OUTCOME DEFINITIONS AND PREDICTORS IN DEPRESSION

Background: The definition of outcome in antidepressant treatment stud ies may be a crucial factor influencing the relationship between possi ble treatment variables and treatment response. We therefore wanted to investigate possible relationships between baseline severity of depre ssion and anxiety, and different definitions of outcome among outpatie nts with major depressive disorder undergoing antidepressant treatment . Methods: Two hundred and forty-eight patients diagnosed with major d epression with the Structured Clinical Interview for DSM-III-R Diagnos is - Patient Edition were treated with fluoxetine 20 mg/day for 8 week s. Patients were evaluated both pretreatment and posttreatment with th e 17-item Hamilton Rating Scale for Depression (Ham-D-17), the Clinica l Global Impressions Scales for Severity (CGI-S) and Improvement (CGI- I). We chose four continuous definitions of response using a linear re gression method to analyze the relationship to baseline anxiety and de pression. We used a logistic regression analysis for the relationship between seven categorical definitions of response and baseline severit y of depression and anxiety. Results: Greater endpoint severity was si gnificantly positively related to greater baseline severity of depress ion and anxiety. Lesser baseline severity of depression or anxiety pre dicted a greater degree of response on either the endpoint CGI-I score (with lower scores indicating greater improvement) or the percent cha nge in HAM-D-17 score (with higher percent change indicating greater i mprovement). For all seven categorical definitions of response, lower baseline scores were significantly related to the probability of being a responder. Conclusions: These findings support the impression that how outcome is defined affects the strength and direction of observed relationships with predictive variables. Methodological implications a re discussed.