Background. - Treatment with low-dose interferon alpha (IFN-) is often associated with neuropsychiatric side effects. In addition to depression and anxiety, IFN- associated cognitive impairment significantly affects patient's mental health and quality of life.

Aims of the study. - To measure possible effects of low-dose IFN- on cognitive functioning and its relationship to the development of depression and anxiety.

Method. - We prospectively followed 38 patients with a chronic hepatitis B or C by neuropsychological tests and psychiatric self-rating scales during 12 weeks of low-dose treatment with IFN-.

Results. - Before IFN- treatment, neuropsychological tests as well as self-ratings in the Beck's Depression Inventory (BDI), the Hospital Anxiety and Depression Scale (HADS) and the Self-Report Symptom Inventory 90 Items-Revised (SCL-90-R) were within the normal range. Following 12 weeks of treatment with IFN- resulted in a slight, but significant increase in depression scores. Neuropsychological assessment after 12 weeks of IFN- treatment showed a significant decrease of the immediate recall in the Auditory-Verbal Learning Test (AVLT) and a significant reduction of words recited in the Controlled Oral Word Association Test (COWA). Cognitive impairment did not significantly correlate with depressive symptoms or anxiety.

Conclusion. - Our results indicate that even low-dose IFN- induces cognitive impairment independent from depressive symptoms, which might be related to functional disturbances in the prefrontal cortex and the hippocampus. We suggest close monitoring of cognitive function during IFN- treatment of chronic hepatitis.