Background

Family and twin studies suggest that juvenile-onset major depressive disorder (MDD) may be etiologically distinct from adult-onset MDD. This study is the first to distinguish prospectively between juvenile- and adult-onset cases of MDD in a representative birth cohort followed up from childhood into adulthood.

Method

The study followed a representative birth cohort prospectively from birth to age 26 years. Early childhood risk factors covered the period from birth to age 9 years. Diagnoses of MDD were made according to DSM criteria at 3 points prior to adulthood (ages 11, 13, and 15 years) and 3 points during adulthood (ages 18, 21, and 26 years). Four groups were defined as (1) individuals first diagnosed as having MDD in childhood, but not in adulthood (n = 21); (2) individuals first diagnosed as having MDD in adulthood (n = 314); (3) individuals first diagnosed in childhood whose depression recurred in adulthood by age 26 years (n = 34); and (4) never-depressed individuals (n = 629).

Results

The 2 juvenile-onset groups had similar high-risk profiles on the childhood measures. Compared with the adult-depressed group, the juvenile-onset groups experienced more perinatal insults and motor skill deficits, caretaker instability, criminality, and psychopathology in their family-of-origin, and behavioral and socioemotional problems. The adult-onset group's risk profile was similar to that of the never-depressed group with the exception of elevated childhood sexual abuse.

Conclusions

Heterogeneity within groups of psychiatric patients poses problems for theory, research, and treatment. The present study illustrates that the distinction between juvenile vs adult-onset MDD is important for understanding heterogeneity within depression.