Does stage of illness impact treatment response in bipolar disorder? Empirical treatment data and their implication for the staging model and early intervention.
OBJECTIVE
The staging model suggests that early stages of bipolar disorder respond better to treatments and have a more favourable prognosis. This study aims to provide empirical support for the model, and the allied construct of early intervention.


METHODS
Pooled data from mania, depression, and maintenance studies of olanzapine were analyzed. Individuals were categorized as having had 0, 1-5, 6-10, or >10 prior episodes of illness, and data were analyzed across these groups.


RESULTS
Response rates for the mania and maintenance studies ranged from 52-69% and 10-50%, respectively, for individuals with 1-5 previous episodes, and from 29-59% and 11-40% for individuals with >5 previous episodes. These rates were significantly higher for the 1-5 group on most measures of response with up to a twofold increase in the chance of responding for those with fewer previous episodes. For the depression studies, response rates were significantly higher for the 1-5 group for two measures only. In the maintenance studies, the chance of relapse to either mania or depression was reduced by 40-60% for those who had experienced 1-5 episodes or 6-10 episodes compared to the >10 episode group, respectively. This trend was statistically significant only for relapse into mania for the 1-5 episode group (p=0.005).


CONCLUSION
Those individuals at the earliest stages of illness consistently had a more favourable response to treatment. This is consistent with the staging model and underscores the need to support a policy of early intervention.