Scalori A et al. (2005) Interferon-induced depression: prevalence and management. Dig Liver Dis 37: 102–107

There is evidence that interferon therapy can cause depression. A recent Italian study has investigated this problem in patients receiving interferon and ribavirin for the treatment of chronic hepatitis C.

Scalori and colleagues used the Minnesota Multiphasic Personality Inventory (MMPI) to assess 185 patients prior to therapy and after 3 months of treatment. Using the MMPI depression scale, patients were categorized as 'normal' (score <60/100) or 'abnormal' (score >60/100). Those in the abnormal category underwent further psychiatric assessment and were treated for depression if necessary.

A total of 18 patients (10%) had positive MMPI tests before therapy and were judged to be at risk of depression; 16 of these patients developed a psychiatric disorder. Of 31 patients (17%) who developed a psychiatric disorder after starting therapy, 11 required antidepressant drugs. When carried out at baseline, the positive and negative predictive values of the MMPI for predicting depression were 0.89 and 0.91, respectively. These values increased to 0.91 and 0.93 when the assessment was repeated after 3 months of interferon therapy.

Scalori et al. recommend that all patients should undergo psychiatric evaluation before starting interferon therapy, and that any cases of depression should be addressed by aggressive treatment.