Response, partial response, and nonresponse in primary care treatment of depression

Depressive disorders are one of the most common reasons for visits to primary care physicians. This study identifies factors related to poor response to depression treatment with selective serotonin reuptake inhibitors (SSRIs) in primary care settings by (1) examining clinical response taking into account treatment, (2) comparing baseline characteristics and outcomes between patients classified by response, and (3) examining characteristics predicting poor response.

A Randomized Trial Investigating SSRI Treatment (ARTIST) was a prospective naturalistic trial comparing effectiveness of SSRI therapy. Eligible patients were randomized to treatment (N = 601) and followed up for 9 months. Treatment patterns were classified as "adequate" (6-month continuous medication), "aggressive" (defined by a treatment algorithm), or "inadequate" (discontinuations) by patient-reported medication use. Clinical response was determined by use of the Symptom Checklist-20 (SCL-20), with patients classified as remitters (score < or =6), partial remitters (50% decrease in symptoms), or nonresponders. Groups were compared on baseline characteristics, functioning, and treatment patterns. Multinomial logistic regression was used to determine predictors of response.

Of patients completing 6-month evaluations (n = 482), 46% were classified as nonresponders. Additionally, 53% (n = 256) received adequate therapy but did not achieve remission and 13% (n = 61) had aggressive therapy associated with treatment resistance. Significant predictors of nonresponse included older age, diagnosis, worse physical functioning, and lower energy level.

A substantial number of adequately treated patients did not respond to antidepressant therapy. Some of these patients may be considered undertreated or treatment-resistant according to current treatment guidelines recommending dose increases or medication switches for less than adequate clinical response.