Depression in youth, between the ages of 10 and 24 years, is both a leading cause of stress and a possible risk factor for future diseases and impairment. Now, a study in the Journal of the American Academy of Child and Adolescent Psychiatry (JAACAP), confirms that depression in childhood or adolescence is associated with higher levels of adult anxiety and substance use disorders, worse health and social functioning, less financial and educational achievement, and increased criminality.

The findings are based on the Great Smoky Mountains Study, an ongoing longitudinal community-based project tracking the health of 1,420 participants from the rural US Southeast that has been ongoing since 1993.

Lead author William Copeland, PhD, and professor in the Department of Psychiatry at the University of Vermont, VA, U.S. said: "One in twelve children struggle with depression at some point between the ages nine and 16, with girls more likely to be affected than boys. This is a common childhood challenge, that, unfortunately, often goes unnoticed by the adults in children's lives, including parents, teachers, and pediatricians.

"The literature is clear that we have effective treatments to help children who are dealing with depression. The problem is that in the real world the majority of children with depression never receive any treatment at all and have to cope with this challenge on their own. This study highlights the consequences of this unmet need."

Children in the study were assessed for depression symptoms through interviews with the children and one of their parents up to eight times between the ages nine to 16. These same participants were then followed up to four times in young adulthood, at ages 19, 21, 25, and 30 to evaluate their mental health and their real world functioning in terms of health, wealth, crime, and social outcomes.

A diagnosis of depression in childhood was associated with a broad range of poorer well-being indicators in adulthood. These links between early depression and poor adult outcomes persisted after accounting for the participants' early exposure to adversities like low socioeconomic status, family problems, abuse and bullying.

The links were strongest for children who chronically displayed high levels of depressive symptoms across childhood rather than those that happened to report symptoms at a single timepoint. This finding is consistent with the idea that persistent depressed mood, in particular, is associated with the worst long-term adult outcomes.

Co-author Iman Alaie, MSc, and a PhD student in the Department of Neuroscience at Uppsala University, Sweden said: "The participants who became depressed as adolescents actually fared worse in the long term than those who had their first bout of depression already in childhood. From a developmental perspective, this was quite an unexpected finding given the current recognition that earlier onset of the disorder may portend poorer outcomes."

The study was not without some good news.

Children who received specialty mental health services to address their mental health challenges were less likely to have worsening mental health problems—particularly anxiety—as they entered adulthood. Even here, however, children who received services continued to display problems in other important areas, including substance use, suggesting that childhood mental health services alone may not be a panacea against all future health problems.

"Our findings underscore the importance of timely and effective treatment, but we should also consider additional support needs during the transition to adulthood," said Ulf Jonsson, an Associate Professor of Child and Adolescent Psychiatry in the Department of Neuroscience, Uppsala University.

Overall, the study affirms the public health burden from childhood depression and depressive symptoms, especially when experienced over longer periods of time. "When we consider the burden of depression on children, their families and school, and look at this from a public health perspective, it becomes clear that we need do a better job alleviating risk factors for childhood depression when possible, having better screening processes to detect childhood depression and to use evidence-based preventions and treatments when we see that a child is at risk for depression or has developed depression," added Lilly Shanahan, Ph.D., professor in the department of Psychology and at the Jacobs Center for Productive Youth Development at the University of Zurich, Switzerland.