We explored the course of bipolar I illness in 172 probands who were f
ollowed up prospectively for up to 5 years. Probands were grouped into
three categories based on whether the symptoms of the index episode w
ere only depressed, only manic, or mixed/cycling. Data were available
for recovery from the index episode, subsequent relapse, and rates of
recovery from the first prospective episode. Pure manic probands had a
significantly faster rate of recovery (median, 6 weeks) than the mixe
d/cycling probands (median, 17 weeks), and the pure depressive proband
s had an intermediate rate (median, 11 weeks). After 5 years of follow
-up the mixed/cycling patients continue to have the lowest cumulative
probability of recovery from the index episode. Mixed/cycling probands
also had a substantially faster time to relapse after recovery from t
he index episode compared with pure manic patients. For those patients
who relapsed, the mixed/cycling patients had the lowest cumulative pr
obability of recovery from the first prospectively observed episode. T
he treatment received by these patients is described and there is a di
scussion of how this treatment may have influenced the findings on cou
rse and outcome.