Preconception to childhood
Events and circumstances occurring early in life, even before birth, affect later mental health. Parents who are prepared emotionally, socially, and economically for having children are most likely to raise healthy, well-adjusted children. Risk factors for later mental health problems occurring preconception or in early childhood include pregnancy during adolescence, low birthweight, perinatal complications, maternal substance use, parental mental illness, family conflict, and child neglect or abuse.  Inadequate prenatal care can lead to low birthweight babies and subsequent behavioral, emotional and learning problems. Substance use during pregnancy increases the likelihood of premature deliveries, low birthweight, and long-term neurological, cognitive, and emotional development problems. Adolescents who become pregnant are less likely to develop employment and survival skills and more likely to experience parental stress; consequently their children are at higher risk of developmental delays and substance-related problems, and are more likely to live under deprived conditions. Prenatal depression, low self-esteem, child care stress, and prenatal anxiety can lead to postpartum depression, which affects bonding and the quality of care given to the infant.
Childhood is a vital time for development of social, cognitive, and emotional skills important in later mental health.[7,8] Protective factors during this period include supportive parenting, feelings of security, positive learning environments, and exercise. Mental health risk factors include violence or conflict, negative life events, lack of connection to school, poor bonding with parents, having a parent with a mental illness, and trauma due to bullying, abuse, or parental loss. Socioeconomic status also impacts opportunities for learning and positive social interaction as well as exposes children to disease and injury.
Many mental disorders manifest their first signs and symptoms on onset during adolescence and early adulthood. In addition to the risks that affect development of younger children, adolescents are vulnerable to tobacco, alcohol, and drug use. Adolescents with family unrest or behavioral problems during childhood are more likely to use drugs and alcohol. Furthermore, academic failure, peer pressure, and media influence are associated with greater substance use which itself is linked to lower educational outcomes, increased violence, and risky sexual behavior.[7,8] Protective factors for mental health among adolescents include problem solving skills, conflict management skills, and safe and supportive communities.
Being able to successfully manage the choices and challenges of adulthood, is dependent on events and circumstances in childhood and adolescence. For example, adolescent pregnancy and a failure to develop skills and good work habits can leave adults inadequately prepared economically. Work-life balance, community involvement, and general health status are also key determinants of mental health in adulthood. Excessive time spent working and caring for others, as well as operating in a difficult or insecure work environment often lead to stress and anxiety. Unemployment and persistent socio-economic pressures, in particular, are associated with poor mental health, higher health care usage, and increased mortality.[6,8]
Inability to participate in the community due to lack of access, neighborhood violence or crime, or having burdensome child- or elder-care responsibilities can lead to social exclusion and loneliness in the individual and an absence of social capital in the community. Furthermore, poor physical health co-occurs with poor mental health, especially depression. Mental Health is negatively affected by both the presence of or treatment for serious medical illnesses—including diabetes, cancer, cardiovascular disease, asthma, and Parkinson’s disease—and many risk behaviors for chronic disease—including low physical activity, tobacco use, alcohol consumption, and a lack of sleep.[5,9] Additional risk factors for poor mental health include personal or family history, excessive substance use, rapid social change, experiencing discrimination, and major life changes, trauma, or stress.[5,6] Protective factors include the ability to cope with stress, the ability to deal with adversity, problem-solving skills, literacy, social support from family and friends, and social and conflict management skills.
Older adults are at particularly high risk for mental health issues resulting from social isolation and chronic disease. Social isolation is common as older adults withdraw from the labor market, and lose partners and friends to illness and death. Social isolation and chronic disease are significant predictors of depression in older adults.
Persons with a large number of protective factors and few risk factors over a lifetime are at increased likelihood for good mental health while those adversely affected by social determinants of health are at increased risk of poor mental health. Social determinants of health affect mental health both directly—through unmitigated (chronic) stress and epigenetic mechanisms—and indirectly—by influencing healthy behaviors, and access to safe housing and healthcare. People with lower education, income, and/or social status, and those who experience discrimination on the basis of race, gender, social class, or other characteristics are at a particularly high risk of mental illness. Figure 2 shows the co-dependency of mental health risk factors and economic vulnerabilities on mental health status.
Mental health among prisoners and inmates
More than half of all male and almost three quarters of female prisoners and inmates suffer from mental illness. Inmates and prisoners with a mental illness are twice as likely to have been homeless in the year prior to incarceration or to have lived in a foster home, agency, or institution while growing up. Availability of appropriate mental health care can reduce the risk of incarceration among persons with mental illness.
Mental health and children and adolescents in the Child Welfare System
Children and adolescents in the Child Welfare system are 4 times more likely to have a mental disorders compared to children in the general population. These children are particularly vulnerable to mental illness due to histories of child abuse and neglect, separation from their biological parents, placement instability, and inability to access appropriate and continuous mental health care.
Mental health among the homeless
The prevalence of mental illness among homeless persons is estimated to be between 40 and 70 percent. The relationship between homelessness and deteriorating mental health is complicated with each further contributing to the other. While lack of affordable housing is the main driver for homelessness, presence of a mental disorder can make it difficult for someone to care for themselves, alienate them from their friends and family, and cause them to be unable to maintain a job and subsequently their home. Likewise, homelessness is traumatizing and can lead to depression, substance abuse, and declining mental and physical health.