Depression is common in rheumatoid arthritis (RA) populations and has been hypothesized to result from patients' belief that they cannot control their disease or its impact. In a sample of 106 patients with RA, we found that scores on a measure of helplessness mediated the relationship between severe, disabling RA and depression. Further, this association was independent of the previously demonstrated correlation between cognitive distortion and depression in RA patients. Thus, both helplessness and cognitive distortion may be important factors in the development and treatment of depression among RA patients.