Neurobehavioral effects of interferon therapy.

Interferon (IFN) therapy is associated with neuropsychiatric side effects including cognitive dysfunction and mood syndromes of varying severity. These problems are the most common causes of treatment discontinuation. Dose and duration of treatment influence risk of IFN-induced side effects. Rates of IFN-induced depression vary, but approach 50% in recent studies. Presence and severity of depressive symptoms at or before treatment predicts development of mood disorders during IFN therapy. Several possible endocrine and neurotransmitter perturbations may be responsible for IFN neurotoxicity, with recent research suggesting different symptoms clusters are related to different underlying mechanisms. The interpretation of these clusters has been influenced by subjective versus objective evaluation of cognitive function. Effective management of IFN-induced neuropsychiatric side effects should involve pretreatment screening and interval assessment during therapy. Antipsychotic and psychostimulant drugs may be used against cognitive dysfunction. Antidepressants have been shown to be effective against IFN-induced depression and can be very valuable in support of adequate or completed therapy.