An early age at bipolar disorder onset is associated with increased depressive morbidity, results from a US study show.
The team found that bipolar disorder patients with an age at onset of 20 years or younger (early onset) spent 20% more weeks in depressive episodes over a mean follow-up period of around 18 years compared with patients with an older age at disease onset.
Williams Coryell (University of Iowa, Iowa City) and team studied 427 individuals with bipolar disorder who were divided into early-onset, middle-onset (21-29 years), and late-onset (≥ 30 years) groups. The mean follow-up period for each group was 17.5, 18.0, and 17.5 years, respectively.
At baseline, patients in the early-onset group had a higher median number of previous depressive episodes than patients in the other two groups combined, at 3.0 versus 1.5 episodes. They were also more likely to have history of suicide attempts (45.2 vs 34.0%) and panic attacks (31.6 vs 20.4%).
During follow up, patients with early-onset bipolar disorder spent a mean 39.9 weeks in depressive episodes, compared with 31.6 weeks for middle-onset patients, and 35.1 weeks for late-onset patients.
Further analysis showed that early age at onset, but not current age, was a significant predictor of depressive morbidity during follow up, while neither age at onset nor current age predicted time in manic or hypomanic episodes.
Coryell and colleagues conclude in the Journal of Affective Disorders: "An early age of onset conveys, to a modest degree, a poorer prognosis as expressed in more depressive morbidity."
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