17 At intake into the CDS, each participant included in the analyses met criteria lor major depressive disorder had no history of mania, hypomania, or schizoaffective disorder and had no underlying minor or intermittent depression of

at least 2 years’ duration. The analyses included 285 participants who recovered from their intake episode and then had at least one recurrent affective episode over the course of the follow-up period. This was done to accommodate the variables included in the propensity model (as described below). The 285 participants had 3141 different antidepressant selleckchem exposure intervals over the course of time. Each of these intervals constituted a unit of analysis, each with its own propensity Inhibitors,research,lifescience,medical score – based strictly on variables assessed prior to the start

Inhibitors,research,lifescience,medical of the interval. Hence both treatment and propensity for treatment were time-varying, as might be seen in clinical practice. Classification of antidepressant exposure Participants were classified based on the ordinal categorical antidepressant dose they received during each week of follow-up. Four ordered categorical antidepressant doses ranged from no treatment to, for example, ≥300 mg imipramine or >30 mg fluoxetine. (Categorical doses for 14 antidepressants are described in Inhibitors,research,lifescience,medical detail elsewhere17,18). A change from one antidepressant to another did not initiate a new exposure interval, but instead extended the current interval duration, unless Inhibitors,research,lifescience,medical the categorical dose was modified. Use of concomitant medications had no bearing on weekly exposure classification. The unit of analysis in both examples presented here is “antidepressant

exposure interval,” which is defined as a period ol consecutive weeks during which the categorical antidepressant dose classification remained unchanged. This is in Inhibitors,research,lifescience,medical contrast to most studies where the unit of analysis is the participant per se. Propensity model A mixed -effects ordinal logistic regression model examined the propensity lor treatment intensity. Treatment intensity was the ordinal-dependent variable, with lour ordered categorical antidepressant Thalidomide doses as described earlier.18,17 Demographic and clinical variables hypothesized to be associated with treatment intensity were included as independent variables in the propensity model. The results indicate that those who had more severe depressive symptoms, more prior episodes, and more intensive somatic therapy in the past were significantly more likely to receive higher antidepressant doses. This suggests that the prior course of illness was more difficult for those who subsequently received higher doses. Nevertheless, treatment comparisons could be made by stratifying effectiveness analyses on the propensity score because the propensity adjustment removed or greatly reduced the magnitude of the association between each propensity variable and antidepressant dose.