American Medical Association, Archives of General Psychiatry, 3(59), p. 215
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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.