Emerging research highlights the importance of the timing of the onset of a depressive episode. This study examines the risk factors and psychiatric features of participants who experienced their first major depressive episode as children, teenagers or adults. This study is unique in that it emphasises the importance of examining onset of an episode during critical developmental periods.

Participants were 372 depressed outpatients who were either treated with psychotherapy (IPT or CBT) or medication as part of two separate randomised clinical trials. Participants completed a number of assessment measures including clinician ratings of DSM diagnoses. Personality was also assessed using Cloninger's (e.g., 1994) Temperament and Character Inventory.

Participants with childhood onset and teenage-onset depression had a higher number of co-morbid diagnoses and more DSM III/IV personality disorder diagnoses than those with adult-onset depression. Specifically, more participants with childhood or teenage onset depression had diagnoses of avoidant and borderline personality disorder. Women who had childhood onset depression were over three times more likely to have attempted suicide compared to other participants. Participants with childhood onset depression were also more likely to report being threatened with abuse, have experienced psychological abuse and reported more abuse incidents. Age of onset was also associated with a number of differences in temperament and character.

This research emphasises the significance of understanding the age of onset of a depressive episode. Depressive episodes that begin in childhood/adolescence are associated with higher co-morbidity and greater personality dysfunction.