Predictors of Outcome in a Primary Care Depression Trial

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.