Predictors of treatment response in obsessive-compulsive disorder: multivariate analyses from a multicenter trial of clomipramine.

There have been many attempts to find predictors of the therapeutic response to the clomipramine treatment of obsessive-compulsive disorder. The majority of studies have failed to identify such predictors. Possible reasons for this failure include the small sample size of most studies, samples homogeneous with respect to the study factors of interest, and the use of statistical procedures that are insensitive to individual differences or that inadequately control for confounding. We have reanalyzed data from Ciba-Geigy's large, multicenter clinical trial of clomipramine for obsessive-compulsive disorder, using stratification and regression techniques to identify multiple prognostic factors and control for confounders. We assessed the relationship between therapeutic response and baseline measures such as severity of symptoms, type of symptoms (obsessions, compulsions, depression), length of illness, age of onset, and other demographic factors (age, race, and sex). We found age of onset to be a strong predictor of response to clomipramine: people who develop obsessive-compulsive disorder later in life have a better chance of responding than do those who become ill earlier, independent of length of illness. We also found that baseline depression is associated with response, but the association appears to be nonlinear.