Gundel LK, et al. - The association between non-affective mental disorders in childhood/adolescence and later depression was investigated. This nationwide prospective cohort study revealed that children and adolescents with non-affective mental disorders were at considerably increased absolute and relative risks of developing depression in young adulthood, particularly females diagnosed with anxiety- or eating disorders in adolescence. These findings could help in identifying groups of children and adolescents at very high risk of developing depression.

• The clinicians performed a nationwide register-based prospective cohort study of individuals with and without non-affective mental disorders early in life.
• They estimated cumulative incidences and incidence rate ratios (IRR) for later depression.

• For a mean of 9.14 years, 475,213 females and 484,813 males born 1990-2007 were followed (contributing a total of 8,778,331 person-years of observation).
• The clinicians diagnosed 7,963 (5,451 females) with depression in the cohort.
• Depression was more common in individuals with prior non-affective mental disorders in adolescence (15.98% in females and 7.02% in males) and in childhood (4.98% in females and 1.6% in males), compared to the background population (3.94% and 1.3% in females; 1.37% and 0.47% in males).
• In childhood/adolescence, eating and anxiety disorders carried the highest absolute risk of depression.
• When compared to youths without such disorders, the relative risk of depression was particularly high the first year after the first non-affective disorder (IRR=15.5; 14.07-17.10), but remained highly elevated more than five years after the first non-affective diagnosis (IRR=2.05; 1.84-2.28).