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.