Depression from preschool to adolescence - five faces of stability.

Background: The term 'stability' has different meanings, and its implications for the etiology, prevention, and treatment of depression vary accordingly. Here, we identify five types of stability in childhood depression, many undetermined due to a lack of research or inconsistent findings.

Methods: Children and parents (n = 1,042) drawn from two birth cohorts in Trondheim, Norway, were followed biennially from ages 4-14 years. Symptoms of major depressive disorder (MDD) and dysthymia were assessed with the Preschool Age Psychiatric Assessment (only parents) and the Child and Adolescent Psychiatric Assessment (age 8 onwards).

Results: (a) Stability of form: Most symptoms increased in frequency. The symptoms' importance (according to factor loadings) was stable across childhood but increased from ages 12-14, indicating that MDD became more coherent. (b) Stability at the group level: The number of symptoms of dysthymia increased slightly until age 12, and the number of symptoms of MDD and dysthymia increased sharply between ages 12-14. (c) Stability relative to the group (i.e., 'rank-order') was modest to moderate and increased from ages 12-14. (d) Stability relative to oneself (i.e., intraclass correlations) was stronger than stability relative to the group and increased from age 12-14. (e) Stability of within-person changes: At all ages, decreases or increases in the number of symptoms forecasted similar changes two years later, but more strongly so between ages 12-14.

Conclusions: Across childhood, while most symptoms of MDD and dysthymia become more frequent, they are equally important. The transition to adolescence is a particularly vulnerable period: The depression construct becomes more coherent, stability increases, the level of depression increases, and such an increase predicts further escalation. Even so, intervention at any time during childhood may have lasting effects on reducing child and adolescent depression.