11.2: Physical Health and Growth in Early Adulthood

Learning Objectives

By the end of this section, you will be able to:

• Identify major features in physical health and change across early adulthood
• Describe the markers of physical maturity that appear and are completed during early adulthood
• Identify lifestyle choices that promote healthy outcomes for early adulthood and beyond

Elisa was so excited to move into her dorm room for her first year of college. However, by the end of her first semester, she felt like life was better back at her mom’s house. Though she was getting good grades, she had stopped exercising, wasn’t sleeping enough, and was eating take out or fast-food for most of her meals. She just didn’t have the energy she used to have before college and noticed that she often had circles under her eyes. Over the winter break, Elisa decided to make changes to her lifestyle to help her feel more energized. She realized enjoying her newfound freedom at college had led to some unhealthy lifestyle choices and that this wasn’t how she wanted to live her life.

Becoming an adult means becoming more responsible for managing our eating, sleeping, and exercise habits. Learning more about what to expect during this period and how our habits affect our health can benefit our overall well-being. In this section, we’ll cover changes in the body during emerging adulthood.

Physical Changes in the Body

Development and physiological changes continue over the entire lifespan. Although the physical transition from childhood to adolescence is easy to see with significant changes in height, weight, and strength, just as some examples, the transition from adolescence to early adulthood may sometimes be more subtle. Part of the reason for this is that the transition to early adulthood involves certain processes stopping. For example, height no longer increases, and our primary and secondary sexual characteristics are donewill complete their process of developing by early adulthood (Hochberg & Konner, 2020).

In general, many of our physical capabilities are at their peak during emerging early adulthood, including muscle strength (Francis et al., 2017), lung function (Mahmoud et al., 2023) hearing (Irace et al., 2021), and immune system functioning (Brodin & Davis, 2017). Let’s consider specific changes to a few of our major body systems.

• Bones. Bones stop growing between the ages of 17 and 25 when the epiphyses, the ends of long bones like the ones in our arms and legs, fuse together. The collarbone is the last bone to mature, around the age of 25 (Hughes et al, 2020; Olivares et al., 2020). There’s also an increase in bone mineral density (Hochberg & Konner, 2020; Lantz et al., 2008).
• Joints. The quality and amount of synovial fluid, the lubricant keeping joints healthy, starts to show some minimal decline as early as age 28, which can lead to increased stiffness (Temple-Wong et al., 2016). For individuals who have had an injury, such as athletes or from an accident, post-traumatic arthritis osteoarthritis may also occur (Punzi et al., 2016).
• Skin. The level of collagen, a substance that helps keep skin firm and elastic, peaks at 25 and slowly declines afterwards (Reilly & Lozano, 2021).
• Body composition. The percentages of both fat and muscle tend to increase during early adulthood, (Hochberg & Konner, 2020), although muscle mass increases more for people assigned male at birth and fat mass increases more for people assigned female at birth (Lantz et al., 2008). Body fat percentage shows a steady gradual increase starting in emerging adulthood for people assigned female at birth, but for people assigned male at birth, this figure dips around age 20 and then rises at a rate similar to that for people assigned female at birth, although overall body fat percentage tends to remain lower (Westerterp, 2018).
• Endocrine system. Testosterone peaks sometime between the late teens and mid 20s and then remains stable until middle age (Hochberg & Konner, 2020; Hull et al., 2011). Fasting glucose levels drop in adolescence and the early parts of emerging adulthood, starting to rise after age 25 (Hammel at al., 2022); similarly, insulin resistance increases after age 20 (Zhong et al., 2019).

Though people within early adulthood are typically at their healthiest, genetic predispositions for health conditions such as heart disease and high blood pressure, when present, can start to influence health during this time. Drinking and drug use, often associated with young people exploring life for the first time on their own, can also contribute to health problems (Table 11.1).

Table 11.1 Summary of Changes in Bodily Systems during Young Adulthood

Bodily System	Changes	Result
Bones	Ends of bones fuse Increased bone density	Strong bones
Joints	Synovial fluid declines as early as age 28	Stiff joints
Skin	Collagen declines after age 25	Skin wrinkles
Body composition	Fat and nonfat tissue increase early Nonfat tissue declines in mid-20s (for men)	Increases in body fat and muscle Decline in muscle amount and strength
Endocrine function	Testosterone peaks (for AMAB) Fasting glucose levels drop Insulin resistance increases	Height of reproductive ability Glucose tolerance declines

Foundations for Health

The choices we make during young adulthood, especially lifestyle choices and our responses to sociocultural influences, can have both immediate and long-term influences on health. New health challenges may arise, such as increases in overweight/obesity, substance use, mental health challenges, and being a victim or perpetrator of gun violence. But there are also many opportunities for positive influences on health and establishing productive habits. While we can’t control every aspect of our health, we can take steps to maintain or even enhance our physical and mental well-being.

Diet and Exercise

Healthy habits established early influence later well-being, especially cardiovascular health (Liu et al., 2012). For example, a healthy diet and a physically active lifestyle can help to protect cardiovascular health, even if a person has a genetic predisposition toward heart disease (U.S. Preventative Services Task Force, 2020). Physical activity builds and maintains muscle, bone, and joint health and improves strength (Figure 11.5). Being moderately active can also help maintain the health and functioning of the heart and lungs, counteract the negative effects of stress, and reduce blood pressure (Chen et al., 2020). In fact, many disorders can be kept in check with proper diet, exercise, and sleep.

Figure 11.5 Exercise has many potential benefits for our physical and mental well-being. (credit: modification of work “Participants of the Boot Camp Challenge training program perform slaloms during a session Aboard the Marine Corps recruit Depot San Diego CA Aug. 23, 2011” by Lance Cpl. Katalynn M. Thomas/Wikimedia Commons, Public Domain)

Education may also have a protective influence on health during early adulthood and beyond. Research using data from the National Longitudinal Study of Adolescent to Adult Health (AKA Add Health) suggests people with higher levels of education tend to have healthier behavioral “profiles” or habits (Skalamera & Hummer, 2016). Admittedly, these are correlational data, so we can’t definitively say that getting more education causes people to have healthier habits. It could be that having more education increases income, which increases access to resources such as gyms, healthy food, and medical care. This doesn’t mean that individuals in early adulthood need to restrict their diets to green smoothies and spend all of their time at the gym. Rather, they should understand that eating healthy food and being active are important, though often challenging with busy schedules.

One way to make healthy behaviors more manageable is to think of them as smaller tasks that can be done over time. For example, the American Heart Association (AHA) recommends that adults get 150 minutes (2.5 hours) of moderate intensity aerobic activity each week (American Heart Association, 2024), but that 150 minutes isn’t meant to be done all at once. Also, physical activity can include things like brisk walking, gardening, and dancing, meaning that people can stay active in a variety of ways. The AHA recommendations also encourage 75 minutes of high-intensity aerobic activity (swimming laps, running, singles tennis) each week and muscle-strengthening activities such as weightlifting two days a week, but emphasize that any activity is better than none (American Heart Association, 2024).

Life Hacks: Stress Management

Another important factor in long-term health is stress management. Excessive stress over time eventually affects multiple aspects of our overall level of health (Seiler et al., 2020). Stress causes your brain to turn on the flight or fight response, which in turn causes the adrenal glands to release the hormones adrenaline and cortisol. Adrenaline increases the activity of our cardiovascular system, so our heart rate and blood pressure rise; if this happens repeatedly or lasts a long time, this puts strain on our heart and can lead to hypertension and stroke. Cortisol causes our liver to release glucose (sugar), which over time can lead to Type 2 diabetes (Cleveland Clinic, 2021) and weakens our immune system (O’Connor et al., 2021). Long-term stress is also associated with increased risk of developing specific health problems such as cancer (Dai et al., 2020), respiratory infections, skin diseases like psoriasis (Graubard et al., 2021), and cardiovascular disease (O’Connor et al., 2021).

So how do we reduce stress? There’s no one solution that works for everyone, but here are some things to try.

• Relax. This is harder than it sounds, because most of us can’t just relax on command. However, we can consciously tense and release our muscles or try to control our breathing. For example, a technique called 4-7-8 breathing (where you inhale to a count of four, hold your breath for a count of seven, and exhale to a count of eight) is common in several yoga practices and has been associated with improved heart rate and blood pressure (Vierra et al., 2022). There are also relaxation apps that use breathing and mindfulness exercises to reduce stress.
• Move. Raising your heart rate to decrease your stress might seem counterintuitive, but exercise can reduce muscle tension and regulate our breathing as well as benefiting our cardiovascular health. Depending on exactly what we do, exercising might also help us feel a sense of accomplishment (e.g., we set a new personal record), enjoy the company of others (e.g., walking with a friend), or simply be a distraction from stressful life events (e.g., clearing your mind in a yoga class). Movement doesn’t even have to mean “exercise”; dancing and pushing a lawn mower may have the same types of physical and psychological benefits.
• Prioritize. Stress often involves feeling overwhelmed by responsibilities, but not everything has to be done immediately. One method of prioritizing tasks is called the Eisenhower Matrix, which asks you to classify tasks along two dimensions: How urgent they are, and how important they are. Tasks that are both urgent and important, like refilling a prescription you’re about to run out of, should be done immediately. Tasks that are important but not urgent, like exercising, can be put off until later (but still need to be done). Tasks that are urgent but not important, like grocery shopping, can be delegated to someone else. Finally, tasks that are neither urgent nor important, like rearranging your furniture, can be deleted or ignored.

Figure 11.6 The Eisenhower Matrix classifies tasks along two dimensions: urgency and importance. (CC BY 4.0; Rice University & OpenStax)

You can also use a calendar or to-do list to figure out the most important things on your plate and leave other things for later.

• Communicate. Talk about the things that are bothering you, either with a therapist or with someone in your life. Ask for help if you need it. No one likes asking for help, but people like helping. Remember how good you feel when you can help someone else out, and give someone else the chance to have that same feeling (plus this might give you less to do).

Healthy Sleep

Many young adults have trouble getting a good night’s sleep, and stress and anxiety are among the primary reasons (Suni & Truong, 2023). Sleep matters because it lets the body repair itself at the cellular level. Physical complaints associated with poor sleep include migraines, neck pain, and a poorer sense of self-rated health (Sohn et al., 2021; Wacks & Weinstein, 2021). Poor sleep can also increase our risk of getting sick, reduce our mental and physical health, and cause premature aging at the cellular level (Carroll & Prather, 2021).

The National Institutes of Health (NIH) recommend that adults get seven to eight hours of sleep per night. The effects of lost sleep are cumulative and produce a “sleep debt”; for example, a person who loses two hours of sleep each night for seven days has a sleep debt of 14 hours (2022). Routinely getting less than seven hours a night can make it difficult to think clearly because chronic sleep deprivation appears to damage brain tissue in areas like the prefrontal cortex and hippocampus (Schiel et al., 2023). Cognitive complaints linked to poor sleep include impaired working memory, attention, and numerical processing (Wacks & Weinstein, 2021). Poor sleep is also a risk factor for developing depression (Fang et al., 2019) and other mental health problems such as anxiety disorders and alcohol use (Daniyal et al., 2022; Wacks & Weinstein, 2021), although it’s not clear whether this is due to disrupted circadian rhythms, changes in levels of neurotransmitters like serotonin, or other factors such as coping mechanisms (Riemann et al., 2020). Regardless of the mechanism behind it, without consistently good sleep, both our physical health and mental health suffer.

Using cell phones and other electronic devices appears to be linked to health in several areas, including sleep. Research has consistently indicated an association between heavy cell phone use and declines in sleep quality and quantity, including taking longer to get to sleep, waking up more frequently (and often using the phone during these awakenings), and decreased REM sleep (Daniyal et al., 2022; Sohn et al., 2021; Wacks & Weinstein, 2021). People who report heavy cell phone use and poorer sleep also report numerous physical, cognitive, and mental health complaints identical to the ones mentioned in the previous paragraph.

Exactly why electronic device use is linked to poorer sleep is unclear. Some research suggests that the blue light emitted by electronic devices suppresses melatonin release, therefore disrupting circadian rhythms (e.g., Silvani et al., 2022); however, other research disputes this (e.g., Blume et al., 2024). It’s also possible that using these devices produces emotional arousal that interferes with sleep, causes people to lose track of time and stay up later than they intended, and/or disrupts the association between bed and sleeping (Alshobaili & AlYousefi, 2019; Suni & Rosen, 2024). Regardless of the underlying mechanism, using electronic devices in bed and/or close to bedtime is reliably associated with negative effects on well-being and functioning (Daniyal et al., 2022; Silvani et al., 2022; Sohn et al., 2021; Wacks & Weinstein, 2021). Interestingly, the overall duration of phone use may be less important than how close to bedtime someone uses their phone (Sohn et al., 2021).

Contextual and Cultural Influences on Health

Research has found that having low socioeconomic status early in life can influence well-being and health over the person’s lifetime (Trent et al., 2019; Wickrama et al., 2022; Yang et al., 2017). Being in the lowest 25 percent SES was found to be particularly disadvantageous to long-term health (Yang et al., 2017). In addition to lacking resources to become and stay healthy, people with lower SES encounter are at a higher risk of adverse life events, such as job loss. Having a more limited set of socioeconomic resources is also associated with higher stress and higher instability (Landberg et al., 2019). For those who struggle with chronic poverty this stress can be reflected in health (Beech et al., 2021). Intergenerational transmission of social and economic disadvantages can increase these health and well-being risks for early adults and reduce access to protective factors such as educational opportunities (Vauhkonen et al., 2017; Wagmiller & Adelman, 2009). Government policies and programs, such as tax care credits for low income families, welfare programs, and educational assistance resources can provide opportunities for overcoming these early disadvantages (Van Ryzin et al., 2018; Vauhkonen et al., 2017).

Racial Discrimination

Racial discrimination is associated with decreased feelings of well-being and health, including increased anxiety and depression (Beech et al., 2021). Research (Lei et al., 2021) following over 1,800 people between the ages of 18 and 28 for a decade revealed that the more frequently young people experience discrimination, the higher their risk of developing mental health issues or a problem with substance misuse (or substance abuse), the use of drugs or alcohol in excess or for purposes for which they weren’t intended, leading to problems in physical, social, and/or psychological functioning, often termed substance misuse or problematic substance use in order to avoid stigma of "abuse"; often related to substance use disorder (SUD). The research from Lei et al. (2021) also points to a possible cumulative effect. Black individuals often deal with extra stressors during early adulthood, including discrimination in employment and housing, and in interactions with others at work or school (Beech et al., 2021). The stress caused by discrimination appears to negatively affect people’ social, mental, and physical health (Hope et al., 2015).

The health effects of being a person of color may start early. A 2021 study by the Urban Institute measured the numbers of different groups considered “on track” for healthy developmental outcomes, with “on track” referring to having a variety of potentially beneficial characteristics and life circumstances such as being born into a two-parent family, having good interpersonal and self-control skills, and having an income at least 100 percent above the federal poverty level. While approximately 67 percent of White individuals are born on track for a healthy developmental outcome according to the criteria presented, only 17 percent of Black children and 34 percent of Hispanic children are. By the time people reach thirty years of age, 66 percent of White adults are still on track, while less than 40 percent of Black individuals and 54 percent of Hispanic individuals are (Acs et al., 2021) (Figure 11.7). For Black and Hispanic people in the United States, their chances of attaining successful development generally improve between birth and adulthood, but are consistently lower than the chances of their White peers.

Figure 11.7 The percentage of the population considered “on track” for healthy development—due to having potentially beneficial characteristics and life circumstances such as income and good socioemotional skills—shows variations by race. (credit: modification of work “Percent on Track in Life Stage by Race” by Social Genome Project/Urban Institute, CC BY 2.0)

Gender and Sexuality

For various reasons, women generally live longer than men but are at higher risk of violence, poverty, and physical and mental health problems (e.g., Kettel et al., 2017). A French study of men’s and women’s use of preventive care screenings indicated that women under age 50 received the fewest screenings, particularly for cardiovascular health and suggested that differences in perception of cardiovascular health risk may be partly responsible (Gaye et al., 2022). Other studies have noted that women are more likely than men to live in poverty and be single parents, which are potentially stressful situations (Bassett & Moore, 2013; Christie-Mizell, 2022; Kettel, 2017; Williams & Baker, 2021). In many cases, the intersection of gender with race and SES appears to increase the likelihood of negative outcomes such as depression and health problems (Christie-Mizell, 2022; Williams & Baker, 2021). These studies also noted that the sociocultural norms and gender role expectations for women produce a lot of stress in that women are expected to be self-sacrificing, nurturing, and subservient (Bassett & Moore, 2013; Christie-Mizell, 2022; Kettel, 2017).

Figure 11.8 LGBTQ+ adults may experience discrimination, violence, and even criminal persecution, which can negatively affect their well-being. (credit: modification of work “Dia de los Muertos Festival Canoga Park CA” by Mark Krynsky/Flickr, CC BY 2.0)

The mental and physical health of LGBTQ+ young adults has become the focus of more research in the past decade. In many countries, being LBGTQ+ meets a range of responses, from passive to active social disapproval, to violence, and even criminal persecution. This can produce an environment of chronic stress that negatively affects health. Compared to heterosexual peers, LGBTQ+ emerging adults are more likely to experience homelessness and food insecurity, often starting in adolescence after their home life becomes intolerable (Bowen et al., 2021; Oi, 2023; Tucker et al., 2024). These circumstances were associated with higher rates of depression, anxiety, physical ailments, and drug use (Tucker et al., 2024). Evidence indicates that LGBTQ+ men were likely to experience negative economic consequences starting as they entered their 30s (Oi, 2023), suggesting that their risk of developing health problems due to chronic stress or lack of access to health care would likely increase as they reached middle age (Figure 11.8).

Specific Individual Health Concerns in Early Adulthood

Obesity, drug and alcohol use, and injuries and accidental death are specific health concerns for young adults. You may have heard that weight gain is common during the first year of college. College freshmen often do gain weight, but not that much—typically about 4 kg (8.8 lb) for male students and about 1.8 kb (4 lb) for female students (Beaudry et al., 2019; Winpenny et al., 2020). This may occur because of new and less healthy eating habits than at home, changes in sleep patterns, and reduced activity levels. Thus, stress may affect our health not just through direct changes in the body but also by changing our health-related behaviors.

Obesity (partly indicated by having a body mass index, or BMI, over 30) occurring during adolescence often carries into early and later stages of adulthood (Ng & Cunningham, 2020; Simmonds et al., 2016). BMI, a measure of height and mass, has been used for years to assess future health problems, but it has come under increasing criticism because it merely focuses on height and weight and doesn’t examine body composition. A person with a lot of muscle mass may have the same BMI as a person with a lot of fat tissue, but we probably wouldn’t consider them to be equally healthy. Nor does obesity guarantee health problems. People with a high BMI have a higher risk of developing heart disease than people with a lower BMI; however, once they develop heart disease, people with a high BMI sometimes live longer and in better health than people with a lower BMI who develop heart disease. This is called the obesity paradox (Horwich et al., 2001) and has been consistently, though not universally, demonstrated (e.g., Carbone et al., 2020; Donataccio et al., 2021; Fröhlich et al., 2022). Additionally, it’s possible to have a BMI that’s too low, as in anorexia nervosa or malnutrition. Being thin doesn’t equal being healthy. Some research has indicated that other measures than BMI alone might better indicate obesity related health risks, such as waist circumference, waist-to-hip ratio. and waist-to-height ratio (Harvard T.H. Chan, 2022; Tu, 2022). The American Medical Association has also adopted the policy to use metrics beyond BMI due to the ways BMI can be an inaccurate and misleading measure of body fat, particularly across racial and ethnic groups (AMA, 2023; Tu, 2022).

Social, environmental, and genetic factors all play a role in increasing the risk of becoming obese. Low socioeconomic status has been connected to obesity, but the connection is not yet well understood. It is believed that stress and limited access to high-quality food may play a role (Spinosa et al., 2019). Additionally, a recent systematic review found emerging adulthood as a risk period for both poor mental health and low diet quality. Findings noted a moderate association between diet quality and measures of psychological health such as depression and anxiety (Collins et al., 2022). The young adults studied in this review weren’t exclusively college students, suggesting that it’s the experience of young adulthood, and not just the college environment, that’s most influential here.

Drug and alcohol use also affect health. Though many adolescents experiment with drugs and alcohol, emerging adulthood is the time when substance use is most likely to occur and to set the foundation for possible substance misuse in the future (UNODC, 2018). Emerging adults (18 to 25) are the largest abusers of marijuana, alcohol, anti-anxiety medications, and ADHD medication (de Jonge et al., 2022; National Center for Drug Abuse Statistics, 2023; Schepis et al., 2020). Drugs and alcohol are frequent elements of socialization at bars, parties, clubs, and concerts during emerging adulthood (de Jonge et al., 2022; Martinotti et al., 2020; Strandberg et al., 2020). In fact, certain drugs such as ketamine and MDMA/Ecstasy are known as “club drugs” because of their association with the nightclub scene (Strandberg et al., 2020). Other potential reasons for the increase in substance use during emerging adulthood include curiosity, financial challenges, and ineffective coping mechanisms for dealing with stress caused by increased responsibilities and changing relationships with family and peers (Ibarra-Mejia et al., 2023; Schepis et al., 2020; Zaami et al., 2020). College students (and young adults in general) are more likely to report using alcohol or drugs to cope with stress than getting counseling (Ibarra-Mejia et al., 2023) (Figure 11.9).

Figure 11.9 Being able to legally drink alcohol brings new experiences and challenges. (credit: “Everyone take a drink” by Dani Lurie/Wikimedia Commons, CC BY 2.0)

This trend of drug and alcohol use increasing in emerging adulthood isn’t confined to any specific country or area of the world, but is a global observation (UNODC, 2018). Additionally, it appears to affect emerging adults regardless of educational status. Emerging adults in the workforce appear to also have higher rates of drug and alcohol use than their older coworkers, suggesting that having disposable income is one factor contributing to this behavior (de Jonge et al., 2022; Strandberg et al., 2020). Table 11.2 shows the percentage of adults ages 18–22 in the United States using alcohol and other drugs, broken down by gender and college enrollment status. In general, rates of substance use are roughly equivalent across groups, with the exception of heavy drinking being more prevalent in male college students compared to the other groups.

Table 11.2 Percentage of Adults Ages 18–22 Reporting Using Specific Substances within the Last Month (source: SAMHSA, 2019)

	College Male	College Female	Noncollege Male	Noncollege Female
Marijuana	22.6	19.9	24.8	22.4
Heavy drinking	9.7	6.8	6.9	5.7
Prescription drugs	3.4	3.1	3.1	3.7
Hallucinogens	1.8	1.0	2.6	1.6
Cocaine/crack	1.2	1.4	1.2	1.8
Methamphetamine	0.2	0.0	0.4	0.2

Substance use is correlated with increased risks of mental health difficulties, risky sexual behavior, violent assault, and injuries and death from accidents and motor vehicle crashes (Baskin-Sommers & Sommers, 2006; de Jonge et al., 2022; Martinotti et al., 2020; National Center for Drug Abuse Statistics, 2023). Repeated use of marijuana and other cannabis-containing substances is associated with increased risk of developing schizophrenia spectrum disorders, particularly in male users (Hjorthøj et al., 2023; Martinotti et al., 2020). Approximately 20 percent of HIV cases can be linked to sharing needles for injected drugs (National Center for Drug Abuse Statistics, 2023). Some substance abuse problems start out as recreational use but snowball into addictions; 8.1 percent of adults ages 18–22 reported a diagnosis of alcohol use disorder and 13.1 percent reported a diagnosis of substance use disorder (SAMHSA, 2019). It’s unclear why some people develop these disorders and others don’t, but there doesn’t seem to be a single pathway or risk factor that guarantees this. There instead appear to be many risk factors, including biological (e.g., variations in dopamine function that affect pleasure-seeking behavior), environmental (e.g., adverse childhood events), psychological (e.g., tendency toward risk-taking) and social (e.g., desire to conform (Potenza, 2013). Regardless of the cause, alcohol or substance use disorders can affect a person’s ability to succeed academically, professionally, and socially, and thus interfere with achieving the typical milestones of emerging adulthood (Table 11.3).

Table 11.3 Classes of Drugs and Their Effects

	Stimulants	Sedative-Hypnotics (“Depressants”)	Opiates	Hallucinogens
Examples	Cocaine, amphetamines (including some ADHD medications such as Adderall), methamphetamines, MDMA (“Ecstasy” or “Molly”)	Alcohol, barbiturates (e.g., secobarbital, pentobarbital), Benzodiazepines (e.g., Xanax)	Opium, Heroin, Fentanyl, Morphine, Oxycodone, Vicodin, methadone, and other prescription pain relievers	Marijuana, LSD, Peyote, mescaline, DMT, dissociative anesthetics including ketamine and PCP
Effects on the body	Increased heart rate, blood pressure, body temperature	Decreased heart rate, blood pressure	Decreased pain, pupil constriction, decreased gut motility, decreased respiratory function	Increased heart rate and blood pressure that may dissipate over time
Psychologically addicting?	Yes	Yes	Yes	Yes

Injuries and Accidental Death

Despite the good physical health typical of young adulthood, people in this developmental stage are at increased risk of accidental death from causes such as car accidents, overdose, and drowning. Other risks include suicide and homicide, especially via gun violence.

The leading causes of death for young adults, according to the CDC (2020), are listed in Figure 11.10.

Figure 11.10 Causes of death aren’t equally distributed across the lifespan; some causes are more likely for some age groups than others. (data source: Centers for Disease Control; attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

Unintentional injury is the most common cause of death during emerging adulthood, and most of those injuries (44.6 percent) are caused by car accidents. Many emerging adults find themselves driving more often—to work, school, stores, and so on—and increased mileage can mean more opportunities for accidents to occur. Being exposed to gun violence at a young age is strongly related to being caught in an event that included gun violence later (Beardslee et al., 2021a, 2021b; Semenza et al., 2024). It’s possible that growing up in an environment where guns and violence are common normalizes these things (Beardslee et al., 2021a).

Mental Health in Emerging and Early Adulthood

Mental health is an important part of overall well-being (Figure 11.11). Emerging adulthood can be full of positive experiences alongside major life changes, but almost everyone has some negative experiences as well. Sometimes, potentially unrelated to life experiences, people develop mental health problems such as depression, anxiety, and substance use disorders. Emerging adulthood is often a pivotal time for mental health. A 2022 meta-analysis indicated that worldwide, 48.4 percent of cases of mental illness had an onset before age 18, and 62.5 percent had an onset before age 25, indicating that the prevalence of mental illness increased by 14.1 percent between the ages of 18 and 25. Eating disorders and obsessive-compulsive disorder, were most likely to be diagnosed between the ages of 17–22, and schizophrenia, alcohol use disorder, panic disorder, and personality disorders were most likely to be first diagnosed between the ages of 25–27 (Solmi et al., 2022). Therefore, the early adulthood stage of development may result in first diagnoses of symptoms from mental, physical, and social struggles that may have occurred earlier in life, and are first identified and properly diagnosed as a young adult.

Figure 11.11 Mental health issues can affect many aspects of our well-being. (credit: modification of work “Man sitting on ground” by NappyStock/nappy, Public Domain)

In addition to young adulthood already being a prime time for developing mental health problems, the COVID-19 pandemic added increased stress to people’s lives due to lockdowns, loss of loved ones, worries about health, and disruption of typical activities. During the first two years of the pandemic, depression, anxiety, and loneliness increased for the world’s population in general but for younger people in particular (Birmingham et al., 2023; Horigan et al., 2021; Juvonen et al., 2022; Molock & Parchem, 2022; Wang et al., 2020; World Health Organization, 2021). Interestingly, longitudinal research suggests that loneliness declined after the first two years because adolescents and young adults adapted to using technology for most of their social interactions (Juvonen et al., 2022), an extension of previously noted trends toward increasing use of social networks for peer interaction and communication (Lima et al., 2017).

There is no one leading risk factor for suicide. Many factors appear to play a role in suicides, occurring in four broad categories: individual risk factors, relationship risk factors, community risk factors, and societal risk factors (CDC, 2023)(Figure 11.12). Specific examples of risk factors include racism and bullying, financial difficulties, lack of opportunities (for work or housing), lack of access to health care and mental health care, feelings of being left out, and relationship problems (CDC, 2021; 2023). Some individuals are at higher risk of attempting or dying by suicide, including veterans, American Indian and Alaskan natives, people living in rural areas, men, and sexual/gender minorities (CDC, 2023a).

Figure 11.12 There are several categories of risk factors for suicide, and people may have more than one risk factor from more than category. (CC BY 4.0; Rice University & OpenStax)

Worldwide, 21 percent of gun deaths are from suicide, but this percentage varies among countries. In the United States, suicide accounts for almost two-thirds of gun-related deaths (World Population Review, 2024). While easy access to guns may contribute to this, another possibility is that repeated exposure to violence produces a sense of hopelessness. There are two research findings consistent with this notion. First, in 2022, Black young adults had more gun-related suicides than White young adults for the first time since data started being collected (Semenza et al., 2024). Second, gun carrying has been found to be negatively correlated with future orientation, the ability to think about and plan for what lies ahead, including predicting consequences of one’s actions. People who are low on future orientation may not have high expectations for themselves and/or consider or care about the consequences of their actions, and thus engage in more dangerous behavior or be more likely to die by suicide (Beardslee et al., 2021a).

Link to Learning

If you or someone you know is at risk of suicide, reach out to the National 988 Suicide and Crisis Lifeline for help. Text or call 988 or chat through their website to receive immediate, confidential support.

References

Acs, G., Werner, K., Blagg, K., & Martin, S. (2021). Identifying pathways for upward mobility Urban Institute. https://www.urban.org/sites/default/...d-mobility.pdf

Alshobaili, F. A., & AlYousefi, N. A. (2019). The effect of smartphone usage at bedtime on sleep quality among Saudi non- medical staff at King Saud University Medical City. Journal of Family Medicine and Primary Care, 8(6), 1953–1957. doi.org/10.4103/jfmpc.jfmpc_269_19

American Heart Association. (2024). American Heart Association recommendations for physical activity in adults and kids. https://www.heart.org/en/healthy-liv...vity-in-adults

Baskin-Sommers, A., & Sommers, I. (2006). The co-occurrence of substance use and high-risk behaviors. Journal of Adolescent Health, 38(5), 609–611. https://doi.org/10.1016/j.jadohealth.2005.07.010

Bassett, E., & Moore, S. (2013). Gender differences in the social pathways linking neighborhood disadvantage to depressive symptoms in adults. PloS One, 8(10), e76554. https://doi.org/10.1371/journal.pone.0076554

Beardslee, J., Docherty, M., Mulvey, E., & Pardini, D. (2021a). The direct and indirect associations between childhood socioeconomic disadvantage and adolescent gun violence. Journal of Clinical Child and Adolescent Psychology, 50(3), 326–336. doi.org/10.1080/15374416.2019.1644646

Beardslee, J., Kan, E., Simmons, C., Pardini, D., Peniche, M., Frick, P. J., Steinberg, L., & Cauffman, E. (2021b). A within-individual examination of the predictors of gun carrying during adolescence and young adulthood among young men. Journal of Youth and Adolescence, 50(10), 1952–1969. https://doi.org/10.1007/s10964-021-01464-6

Beech, B. M., Ford, C., Thorpe Jr, R. J., Bruce, M. A., & Norris, K. C. (2021). Poverty, racism, and the public health crisis in America. Frontiers in Public Health, 9, 699049. https://doi.org/10.3389/fpubh.2021.699049

Birmingham, W. C., Wadsworth, L., Lassetter, J. H., Graff, T. C., Lauren, E., & Hung, M. (2023). COVID-19 lockdown: Impact on college students’ lives. Journal of American College Health, 71(3), 879-893. doi.org/10.1080/07448481.2021.1909041

Blume, C., Cajochen, C., Schöllhorn, I., Slawik, H. C., & Spitschan, M. (2024). Effects of calibrated blue-yellow changes in light on the human circadian clock. Nature Human Behaviour, 8(3), 590–605. https://doi.org/10.1038/s41562-023-01791-7

Bowen, E., Ball, A., Jones, A. S., & Miller, B. (2021). Toward many emerging adulthoods: A theory-based examination of the features of emerging adulthood for cross-systems youth. Emerging Adulthood, 9(3), 189-201. doi.org/10.1177/2167696821989123

Brodin, P., & Davis, M. M. (2017). Human immune system variation. Nature Reviews Immunology, 17(1), 21–29. https://doi.org/10.1038/nri.2016.125

Carbone, S., Lavie, C. J., Elagizi, A., Arena, R., & Ventura, H. O. (2020). The impact of obesity in heart failure. Heart Failure Clinics, 16(1), 71-80. https://doi.org/10.1016/j.hfc.2019.08.008

Carroll, J. E., & Prather, A. A. (2021). Sleep and biological aging: A short review. Current Opinion in Endocrine and Metabolic Research, 18, 159-164. https://doi.org/10.1016/j.coemr.2021.03.021

Centers for Disease Control and Prevention. (2022a). Distracted driving. www.cdc.gov/transportationsa...x.html#problem

Centers for Disease Control and Prevention. (2022b). Impaired driving: Get the facts. www.cdc.gov/transportationsa...factsheet.html

Centers for Disease Control and Prevention. (2022c). Risk and protective factors. www.cdc.gov/suicide/factors/index.html

Centers for Disease Control and Prevention. (2023a). Disparities in suicide. www.cdc.gov/suicide/facts/di...n-suicide.html

Centers for Disease Control and Prevention. (2023b). Preventing youth violence. www.cdc.gov/violencepreventi.../fastfact.html

Centers for Disease Control and Prevention. (2020). Injury Data Visualization Tools | WISQARS | CDC. Wisqars.cdc.gov. https://wisqars.cdc.gov/data/lcd/home

Centers for Disease Control and Prevention. (2023b). Suicide data and statistics. www.cdc.gov/suicide/suicide-...tatistics.html

Chen, M. L., Hu, J., McCoy, T. P., Letvak, S., & Ivanov, L. (2020). Associations of lifestyle intervention effect with blood pressure and physical activity among community-dwelling older Americans with hypertension in Southern California. International Journal of Environmental Research and Public Health, 17(16), 5673. https://doi.org/10.3390/ijerph17165673

Christie-Mizell, C. A. (2022). Neighborhood disadvantage and poor health: The consequences of race, gender, and age among young adults. International Journal of Environmental Research and Public Health, 19, 8107. https:// doi.org/10.3390/ijerph19138107

Cleveland Clinic. (2021). Cortisol. my.clevelandclinic.org/healt...22187-cortisol

Collins, S., Dash, S., Allender, S., Jacka, F., & Hoare, E. (2022). Diet and mental health during emerging adulthood: a systematic review. Emerging Adulthood, 10(3), 645-659. doi.org/10.1177/2167696820943028

Dai, S., Mo, Y., Wang, Y., Xiang, B., Liao, Q., Zhou, M., Li, X., Li, Y., Xiong, W., Li, G., Guo, C., & Zeng, Z. (2020). Chronic stress promotes cancer development. Frontiers in Oncology, 10, 1492. https://doi.org/10.3389/fonc.2020.01492

de Jonge, M. C., Bukman, A. J., van Leeuwen, L., Onrust, S. A., & Kleinjan, M. (2022). Latent classes of substance use in young adults - A systematic review. Substance Use & Misuse, 57(5), 769–785. doi.org/10.1080/10826084.2022.2040029

Donataccio, M. P., Angiola, V., & Ottavio, B. (2021). Obesity paradox and heart failure. Eating and Weight Disorders, 26(6), 1697-1707. https://doi.org/10.1007/s40519-020-00982-9

Fang, H., Tu, S., Sheng, J., & Shao, A. (2019). Depression in sleep disturbance: A review on a bidirectional relationship, mechanisms and treatment. Journal of Cellular and Molecular Medicine, 23(4), 2324–2332. doi.org/10.1111/jcmm.14170Francis, P., Lyons, M., Piasecki, M., Mc Phee, J., Hind, K., & Jakeman, P. (2017). Measurement of muscle health in aging. Biogerontology, 18(6), 901–911. https://doi.org/10.1007/s10522-017-9697-5

Fröhlich, H., Frey, N., Frankenstein, L., & Täger, T. (2022). The obesity paradox in heart failure: Is it still valid in light of new therapies?. Cardiology, 147(5-6), 529–538. doi.org/10.1159/000527332

Gaye, B., Hergault, H., Lassale, C., Ladouceur, M., Valentin, E., Vignac, M., Danchin, N., Diaw, M., Kvaskoff, M., Chamieh, S., Thomas, F., Michos, E., & Jouven, X. (2022). Gender gap in annual preventive care services in France. eClinical Medicine, 49, 101469. https://doi.org/10.1016/j.eclinm.2022.101469

Graubard, R., Perez-Sanchez, A., & Katta, R. (2021). Stress and skin: An overview of mind body therapies as a treatment strategy in dermatology. Dermatology Practical & Conceptual, 11(4), e2021091. https://doi.org/10.5826/dpc.1104a91

Hammel, M. C., Stein, R., Kratzsch, J., Vogel, M., Eckert, A. J., Triatin, R. D., Colombo, M., Meigen, C., Baber, R., Stanik, J., Spielau, U., Stoltze, A., Wirkner, K., Tönjes, A., Snieder, H., Holl, R. W., Stumvoll, M., Blüher, M., Kiess, W., & Körner, A. (2023). Fasting indices of glucose-insulin-metabolism across life span and prediction of glycemic deterioration in children with obesity from new diagnostic cut-offs. The Lancet Regional Health Europe, 30, 100652. https://doi.org/10.1016/j.lanepe.2023.100652

Hjorthøj, C., Compton, W., Starzer, M., Nordholm, D., Einstein, E., Erlangsen, A., Nordentoft, M., Volkow, N. D., & Han, B. (2023). Association between cannabis use disorder and schizophrenia stronger in young males than in females. Psychological Medicine, 53(15), 7322–7328. https://doi.org/10.1017/S0033291723000880

Hochberg, Z., & Konner, M. (2020). Emerging adulthood, a pre-adult life- history stage. Frontiers in Endocrinology, 10(918). https://doi.org/10.3389/fendo.2019.00918

Hope, E. C., Hoggard, L. S., & Thomas, A. (2015). Emerging into adulthood in the face of racial discrimination: Physiological, psychological, and sociopolitical consequences for African American youth. Translational Issues in Psychological Science, 1(4), 342–351. doi.org/10.1037/tps0000041

Horwich, T. B., Fonarow, G. C., Hamilton, M. A., MacLellan, W. R., Woo, M. A., & Tillisch, J. H. (2001). The relationship between obesity and mortality in patients with heart failure. Journal of the American College of Cardiology, 38(3), 789–95. https://doi.org/10.1016/s0735-1097(01)01448-6.

Hughes, J. L., Newton, P. O., Bastrom, T., Fabricant, P. D., & Pennock, A. T. (2020). The clavicle continues to grow during adolescence and early adulthood. HSS Journal, 16(S2), 372–377. doi.org/10.1007/s11420-020-09754-8

Hull, H. R., Thornton, J., Wang, J., Pierson, R. N., Jr, Kaleem, Z., Pi-Sunyer, X., Heymsfield, S., Albu, J., Fernandez, J. R., Vanitallie, T. B., & Gallagher, D. (2011). Fat-free mass index: changes and race/ethnic differences in adulthood. International Journal of Obesity, 35(1), 121–127. https://doi.org/10.1038/ijo.2010.111

Ibarra-Mejia, G., Lusk, M., & Umucu, E. (2023). Mental health among college students during the COVID-19 pandemic at a Hispanic-serving institution. Health Promotion Practice, 24(3), 455-464. doi.org/10.1177/15248399221092750

Irace, A. L., Chern, A., & Golub, J. S. (2021). Hearing loss patterns throughout life: Insights from Japan. The Lancet Regional Health–Western Pacific, 10. 100152. https://doi.org/10.1016/j.lanwpc.2021.100152

Juvonen, J., Lessard, L. M., Kline, N. G., & Graham, S. (2022). Young adult adaptability to the social challenges of the COVID-19 pandemic: The protective role of friendships. Journal of Youth and Adolescence, 51(3), 585-597. https://link.springer.com/content/pd...22-01573-w.pdf

Kettel, B. (2017). Women, health, and the environment. In S. Sherwin & B. Parish (Eds.), Women, medicine, ethics and the law (1st ed., pp. 23-35). Routledge. doi.org/10.4324/9781003073789

Landberg, M., Lee, B., & Noack, P. (2019). What alters the experience of emerging adulthood? How the experience of emerging adulthood differs according to socioeconomic status and critical life events. Emerging Adulthood, 7(3), 208–222. doi.org/10.1177/2167696819831793

Lantz, H., Bratteby, L. E., Fors, H., Sandhagen, B., Sjöström, L., & Samuelson, G. (2008). Body composition in a cohort of Swedish adolescents aged 15, 17 and 20.5 years. Acta Paediatrica, 97(12), 1691–1697. doi.org/10.1111/j.1651-2227.2008.01035.x

Lei, Y., Shah, V., Biely, C., Jackson, N., Dudovitz, R., Barnert, E., Hotez, E., Guerrero, A., Bui, A. L., Sastry, N., & Schickedanz, A. (2021). Discrimination and subsequent mental health, substance use, and well-being in young adults. Pediatrics, 148(6). doi.org/10.1542/peds.2021-051378

Lima, M. L., Marques, S., Muiños, G., & Camilo, C. (2017). All you need is Facebook friends? Associations between online and face-to-face friendships and health. Frontiers in Psychology, 08. https://doi.org/10.3389/fpsyg.2017.00068

Liu, K., Daviglus, M. L., Loria, C. M., Colangelo, L. A., Spring, B., Moller, A. C., & Lloyd-Jones, D. M. (2012). Healthy lifestyle through young adulthood and the presence of low cardiovascular disease risk profile in middle age. Circulation, 125(8), 996–1004. doi.org/10.1161/circulationaha.111.060681

Mahmoud, O., Granell, R., Peralta, G. P., Garcia-Aymerich, J., Jarvis, D., Henderson, J., & Sterne, J. (2023). Early-life and health behaviour influences on lung function in early adulthood. The European Respiratory Journal, 61(3), 2001316. doi.org/10.1183/13993003.01316-2020

Martinotti, G., Negri, A., Schiavone, S., Montemitro, C., Vannini, C., Baroni, G., Pettorruso, M., De Giorgio, F., Giorgetti, R., Verrastro, V., Trabace, L., Garcia, A., Castro, I., Iglesias Lopez, J., Merino Del Villar, C., Schifano, F., & di Giannantonio, M. (2020). Club drugs: Psychotropic effects and psychopathological characteristics of a sample of inpatients. Frontiers in Psychiatry, 11, 879. https://doi.org/10.3389/fpsyt.2020.00879

Molock, S. D., & Parchem, B. (2022). The impact of COVID-19 on college students from communities of color. Journal of American College Health, 70(8), 2399–2405. doi.org/10.1080/07448481.2020.1865380

National Center for Drug Abuse Statistics. (2023). Drug abuse statistics. https://drugabusestatistics.org/

National Institutes of Health. (2022). How much sleep is enough. https://www.nhlbi.nih.gov/health/sle...how-much-sleep

National Overview of STDs, 2021. (2023, April 11). Www.cdc.gov. www.cdc.gov/std/statistics/2021/overview.htm

Neal, S., Channon, A. A., Chandra-Mouli, V., & Madise, N. (2020). Trends in adolescent first births in sub-Saharan Africa: a tale of increasing inequity? International Journal for Equity in Health, 19(1). https://doi.org/10.1186/s12939-020-01251-y

O'Connor, D. B., Thayer, J. F., & Vedhara, K. (2021). Stress and health: A review of psychobiological processes. Annual Review of Psychology, 72, 663–688. doi.org/10.1146/annurev-psych-062520-122331

Oi, K. (2023). Widening, narrowing, and persistence of socioeconomic gaps between sexual minorities and heterosexuals across adulthood. Journal of Homosexuality, 70(13), 3213–3246. doi.org/10.1080/00918369.2022.2090885

Olivares, L. A. F., De León, L. G., & Fragoso, M. I. (2020). Skeletal age prediction model from percentage of adult height in children and adolescents. Scientific Reports, 10, 15768. https://doi.org/10.1038/s41598-020-72835-5

Ozbay, F., Johnson, D. C., Dimoulas, E., Morgan, C. A., Charney, D., & Southwick, S. (2007). Social support and resilience to stress: From neurobiology to clinical practice. Psychiatry (Edgmont), 4(5), 35–40. www.ncbi.nlm.nih.gov/pmc/articles/PMC2921311/

Potenza, M. N. (2013). Biological contributions to addictions in adolescents and adults: prevention, treatment, and policy implications. The Journal of Adolescent Health, 52(2 Suppl 2), S22–S32. https://doi.org/10.1016/j.jadohealth.2012.05.007

Punzi, L., Galozzi, P., Luisetto, R., Favero, M., Ramonda, R., Oliviero, F., & Scanu, A. (2016). Post-traumatic arthritis: overview on pathogenic mechanisms and role of inflammation. RMD open, 2(2), e000279. doi.org/10.1136/rmdopen-2016-000279

Reilly, D. M., & Lozano, J. (2021). Skin collagen through the lifestages: Importance for skin health and beauty. Plastic and Aesthetic Research, 8(2). https://doi.org/10.20517/2347-9264.2020.153

Riemann, D., Krone, L. B., Wulff, K., & Nissen, C. (2020). Sleep, insomnia, and depression. Neuropsychopharmacology, 45(1), 74–89. https://doi.org/10.1038/s41386-019-0411-y

SAMHSA, Center for Behavioral Health Statistics and Quality (2019). National survey on drug use and health, 2018 and 2019. https://www.samhsa.gov/data/sites/de...ect6pe2019.htm

Schepis, T. S., Klare, D. L., Ford, J.A., & McCabe, S. E. (2020). Prescription drug misuse: Taking a lifespan perspective. Substance Abuse: Research and Treatment, 14. doi.org/10.1177/1178221820909352

Schiel, J. E., Tamm, S., Holub, F., Petri, R., Dashti, H. S., Domschke, K., Feige, B., Goodman, M. O., Jones, S. E., Lane, J. M., Ratti, P.-L., Ray, D. W., Redline, S., Riemann, D., Rutter, M. K., Saxena, R., Sexton, C. E., Tahmasian, M., Wang, H., . . . Spiegelhalder, K. (2023). Associations between sleep health and grey matter Vol. in the UK Biobank cohort (n = 33 356). Brain Communications, 5(4), Article fcad200. doi.org/10.1093/braincomms/fcad200

Seiler, A., Fagundes, C. P., Christian, L. M. (2020). The impact of everyday stressors on the immune system and health. In A. Choukèr (Ed.), Stress challenges and immunity in space (pp. 71-92). Springer. https://doi.org/10.1007/978-3-030-16996-1_6

Semenza, D. C., Daruwala, S., Brooks Stephens, J. R., & Anestis, M. D. (2024). Gun violence exposure and suicide among black adults. JAMA Network Open, 7(2), e2354953. doi.org/10.1001/jamanetworkopen.2023.54953

Silvani, M. I., Werder, R., & Perret, C. (2022). The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review. Frontiers in Physiology, 13, 943108. https://doi.org/10.3389/fphys.2022.943108

Simmonds, M., Llewellyn, A., Owen, C. G., & Woolacott, N. (2016). Predicting adult obesity from childhood obesity: A systematic review and meta-analysis. Obesity Reviews, 17(2), 95–107. doi.org/10.1111/obr.12334

Skalamera, J., & Hummer, R. A. (2016). Educational attainment and the clustering of health-related behavior among U.S. young adults. Preventive Medicine, 84, 83–89. https://doi.org/10.1016/j.ypmed.2015.12.011

Sohn, S. Y., Krasnoff, L., Rees, P., Kalk, N. J., & Carter, B. (2021). The association between smartphone addiction and sleep: a UK cross-sectional study of young adults. Frontiers in Psychiatry, 12, 629407. https://doi.org/10.3389/fpsyt.2021.629407

Solmi, M., Radua, J., Olivola, M., Croce, E., Soardo, L., Salazar de Pablo, G., Shin, J. I., Kirkbride, J. B., Jones, P., Kim, J. H., Kim, J. Y., Carvalho, A. F., Seeman, M. V., Correll, C. U., & Fusar-Poli, P.. (2022). Age at onset of mental disorders worldwide: large-scale meta-analysis of 192 epidemiological studies. Molecular Psychiatry 27, 281–295. https://doi.org/10.1038/s41380-021-01161-7

Spinosa, J., Christiansen, P., Dickson, J. M., Lorenzetti, V., & Hardman, C. A. (2019). From socioeconomic disadvantage to obesity: The mediating role of psychological distress and emotional eating. Obesity, 27(4), 559–564. doi.org/10.1002/oby.22402

Strandberg, A. K., Elgán, T. H., Feltmann, K., Jayaram Lindström, N., & Gripenberg, J. (2020). Illicit drugs in the nightlife setting: Changes in employee perceptions and drug use over a fifteen-year period. Substance Use & Misuse, 55(13), 2116–2128. doi.org/10.1080/10826084.2020.1793365

Suni, E., & Rosen, D. (2024). Mastering sleep hygiene: Your path to quality sleep. Sleep Foundation. https://www.sleepfoundation.org/sleep-hygiene

Suni, E., & Truong, K. (2023). 100+ sleep statistics Sleep Foundation. https://www.sleepfoundation.org/how-...cts-statistics

Temple-Wong, M. M., Ren, S., Quach, P., Hansen, B. C., Chen, A. C., Hasegawa, A., D’Lima, D. D., Koziol, J., Masuda, K., Lotz, M. K., & Sah, R. L. (2016). Hyaluronan concentration and size distribution in human knee synovial fluid: variations with age and cartilage degeneration. Arthritis Research & Therapy, 18, 18. https://doi.org/10.1186/s13075-016-0922-4

Tracy, B. M., Smith, R. N., Miller, K., Clayton, E., Bailey, K., Gerrin, C., Eversley-Kelso, T., Carney, D., & MacNew, H. (2019). Community distress predicts youth gun violence. Journal of Pediatric Surgery, 54(11), 2375–2381. https://doi.org/10.1016/j.jpedsurg.2019.03.021

Trent, M., Dooley, D. G., Dougé, J., Cavanaugh Jr., R. M., Lacroix, A. E., Fanburg, J., Rahmandar, M. H., Hornberger, L. L., Schneider, M. B., Yen, S., Chilton, L. A., Green, A. E., Dilley, K. J., Gutierrez, J. R., Duffee, J. H., Keane, V. A., Krugman, S. D., McKelvey, C. D., Linton, J. M.,…. Wallace, S. B. (2019). The impact of racism on child and adolescent health. Pediatrics, 144(2), e20191765. doi.org/10.1542/peds.2019-1765

Tucker, J. S., Perez, L. G., Klein, D. J., & D'Amico, E. J. (2024). Homelessness and food insecurity during emerging adulthood: Associations with changes in behavioral and physical health over a two-year period. The Journal of Adolescent Health, 74(5), 1006–1011. https://doi.org/10.1016/j.jadohealth.2023.12.007

Van Ryzin, M. J., Fishbein, D., & Biglan, A. (2018). The promise of prevention science for addressing intergenerational poverty. Psychology, Public Policy, and Law, 24(1), 128.

Vauhkonen, T., Kallio, J., Kauppinen, T. M., & Erola, J. (2017). Intergenerational accumulation of social disadvantages across generations in young adulthood. Research in social stratification and mobility, 48, 42–52.

UNODC. (2018). World drug report 2018, Booklet 4.Drugs and age: Drugs and associated issues among young people and older people. https://www.unodc.org/wdr2018/prelau...et_4_YOUTH.pdf

U.S. Preventive Services Task Force. (2020). Behavioral counseling interventions to promote a healthy diet and physical activity for cardiovascular disease prevention in adults with cardiovascular risk factors: U.S. Preventive Services Task Force recommendation statement. JAMA, 324(20), 2069–2075. doi.org/10.1001/jama.2020.21749

Vierra, J., Boonla, O., & Prasertsri, P. (2022). Effects of sleep deprivation and 4-7-8 breathing control on heart rate variability, blood pressure, blood glucose, and endothelial function in healthy young adults. Physiological Reports, 10(13), e15389. doi.org/10.14814/phy2.15389

Wacks, Y., & Weinstein, A. M. (2021). Excessive smartphone use is associated with health problems in adolescents and young adults. Frontiers in Psychiatry, 12, 669042. https://doi.org/10.3389/fpsyt.2021.669042

Wagmiller, R. L., & Adelman, R. M. (2009). Childhood and intergenerational poverty: The long-term consequences of growing up poor. National Center for Children in Poverty. http://www.nccp.org/publication/chil...ional-poverty/

Wang, X., Hegde, S., Son, C., Keller, B., Smith, A., & Sasangohar, F. (2020). Investigating mental health of US college students during the COVID-19 pandemic: Cross-sectional survey study. Journal of Medical Internet Research, 22(9), e22817. https://doi.org/10.2196/22817

Westerterp, K. R. (2018). Changes in physical activity over the lifespan: impact on body composition and sarcopenic obesity. Obesity Reviews, 19 (Suppl. 1), 8-13. doi.org/10.1111/obr.12781

Wickrama, K. (A. S.), Lee, T. K., & O’Neal, C. W. (2022). Explaining physical health disparities and inequalities over the first half of the life course: An integrative review of Add Health studies. Journal of Adolescent Health, 71(6), S47–S54. https://doi.org/10.1016/j.jadohealth.2022.06.019

Williams, D. T., & Baker, R. S. (2021). Family structure, risks, and racial stratification in poverty. Social Problems, 68(4), 964–985. doi.org/10.1093/socpro/spab018

World Health Organization. (2021). Action required to address the impacts of the COVID-19 pandemic on mental health and service delivery systems in the WHO European Region: recommendations from the European Technical Advisory Group on the Mental Health Impacts of COVID-19. iris.who.int/bitstream/handl...-59267-eng.pdf

World Population Review. (2024). Gun deaths by country 2024. https://worldpopulationreview.com/co...ths-by-country

Yang, Y. C., Gerken, K., Schorpp, K., Boen, C., & Harris, K. M. (2017). Early-life socioeconomic status and adult physiological functioning: A life course examination of biosocial mechanisms. Biodemography and Social Biology, 63(2), 87–103. doi.org/10.1080/19485565.2017.1279536

Zhong, V. W., Bancks, M. P., Schreiner, P. J., Lewis, C. E., Steffen, L. M., Meigs, J. B., Schrader, L. A., Schorr, M., Miller, K. K., Sidney, S., & Carnethon, M. R. (2019). Insulin resistance since early adulthood and appendicular lean mass in middle-aged adults without diabetes: 20 years of the CARDIA study. Journal of Diabetes and Its Complications, 33(1), 84–90. https://doi.org/10.1016/j.jdiacomp.2018.09.011