Predictors of outcome in a primary care depression trial

Abstract

Objective: Previous treatment trials have found that approximately one third of depressed patients have persistent symptoms. We examined whether depression severity, comorbid psychiatric illness, and personality factors might play a role in this lack of response.

Design: Randomized trial of a stepped collaborative care intervention versus usual care.

Setting: HMO in Seattle, Wash.

Patients: Patients with major depression were stratified into severe (N = 149) and mild to moderate depression (N = 79) groups prior to randomization.

Interventions: A multifaceted intervention targeting patient, physician, and process of care, using collaborative management by a psychiatrist and primary care physician.

Measurements and main results: Patients with more severe depression had a higher risk for panic disorder (odds ratio [OR], 5.8), loneliness (OR, 2.6), and childhood emotional abuse (OR, 2.1). Among those with less severe depression, intervention patients showed significantly improved depression outcomes over time compared with those in usual care (z = -3.06, P<.002); however, this difference was not present in the more severely depressed groups (z = 0.61, NS). Although the group with severe depression showed differences between the intervention and control groups from baseline to 3 months that were similar to the group with less severe depression (during the acute phase of the intervention), these differences disappeared by 6 months.

Conclusions: Initial depression severity, comorbid panic disorder, and other psychosocial vulnerabilities were associated with a decreased response to the collaborative care intervention. Although the intervention was appropriate for patients with moderate depression, individuals with higher levels of depression may require a longer continuation phase of therapy in order to achieve optimal depression outcomes.

FIGURE 1

SCL depression adjusted means (adjusted for age, gender, chronic disease score, and neuroticism) with standard errors for patients in the high severity strata.

FIGURE 2

SCL depression adjusted means (adjusted for age, gender, chronic disease score, and neuroticism) with standard errors for patients in the low severity strata.