Mental disorders such as anxiety and depression often emerge for the first time during adolescence and early adulthood, with about three-quarters of mental disorders having their first onset before the age of 25 (Kessler et al, 2005). Evidence suggests that incidence rates for depressive disorders increase in early adolescence, with prevalence continuing to rise throughout adolescence (Lewinsohn et al, 1998; Lewinsohn and Essau, 2002; Costello et al, 2003). Age of onset for anxiety varies by disorder, with specific phobia, separation anxiety disorder, social phobia and obsessive compulsive disorder (OCD) most likely to onset during the adolescent years (Kessler et al, 2007, 2009). The experience of mild levels of depressive and anxiety symptoms that do not meet the threshold for diagnosis, but can nevertheless cause significant psychological distress, is also common during adolescence (Hankin, 2006).
This is concerning because of the potential for mental health difficulties that onset at this time to set up developmental cascades of vulnerability, which may extend well into adulthood (Masten and Cicchetti, 2010). Adolescence is a time of prominent transitions, and this developmental stage heralds significant physical, cognitive, psychological, interpersonal and socio-contextual changes (Weir et al, 2012). Depressive or anxiety disorders may interfere with the young person’s capacity to effectively navigate these transitions and complete key developmental milestones (Kessler and Wang, 2009). A failure to detect and treat these conditions in a timely manner can lead to numerous adverse life course consequences (Kessler et al, 2001; Merikangas et al, 2010), which presents a strong moral and economic argument for intervention early in life.