Recombinant preparations of the cytokine interferon (IFN)-α are increasingly used to treat a number of medical conditions, including chronic viral hepatitis and several malignancies. Although frequently effective, IFNα induces a variety of neuropsychiatric adverse effects, including an acute confusional state that develops rapidly after initiation of high-dose IFNα, a depressive syndrome that develops more slowly over weeks to months of treatment, and manic conditions most often characterised by extreme irritability and agitation, but also occasionally by euphoria. Acute IFNα-induced confusional states are typically characterised by disorientation, lethargy, somnolence, psychomotor retardation, difficulties with speaking and writing, parkinsonism and psychotic symptoms. Strategies for managing delirium should be employed, including treatment of contributing medical conditions, use of either typical or atypical antipsychotic agents and avoidance of medications likely to worsen mental status. Significant depressive symptoms occur in 21-58% of patients receiving IFNα, with symptoms typically manifesting over the first several months of treatment. The most replicated risk factor for developing depression is the presence of mood and anxiety symptoms prior to treatment. Other potential, but less frequently replicated, risk factors include a past history of major depression, being female and increasing IFNα dosage and treatment duration. The available data support two approaches to the pharmacological management of IFNα-induced depression: antidepressant pretreatment or symptomatic treatment once IFNα has been initiated. Pretreatment might be best reserved for patients already receiving antidepressants or for patients who endorse depression or anxiety symptoms of mild or greater severity prior to therapy. Several recent studies demonstrate that antidepressants effectively treat IFNα-induced depression once it has developed, allowing the vast majority of subjects to complete treatment successfully. Recent data suggest that IFNα-induced depression may be composed of two overlapping syndromes: a depression-specific syndrome characterised by mood, anxiety and cognitive complaints, and a neurovegetative syndrome characterised by fatigue, anorexia, pain and psychomotor slowing. Depression-specific symptoms are highly responsive to serotonergic antidepressants, whereas neurovegetative symptoms are significantly less responsive to these agents. These symptoms may be more effectively treated by agents that modulate catecholaminergic functioning, such as combined serotonin-noradrenaline (norepinephrine) antidepressants, bupropion, psychostimulants or modafinil. Additional factors to consider in selecting an antidepressant include potential drug-drug interactions and adverse effect profile. Finally, IFNα appears capable of inducing manic symptoms. Mania, especially when severe, is a clinical emergency. When this occurs, IFNα and antidepressants should be stopped, an emergency psychiatric consultation should be obtained, and treatment with a mood stabiliser should be initiated. © 2005 Adis Data Information BV. All rights reserved.

Background: There has been increasing interest in the role of immunologic processes, notably cytokines, in the development of behavioral alterations, especially in medically ill patients. Interferon (IFN)-α is notorious for causing behavioral symptoms, including depression, fatigue, and cognitive dysfunction, and has been used to investigate the effects of cytokines on the brain. Methods: In the present study we assessed the effects of low-dose IFN-α on brain activity, using functional magnetic resonance imaging during a task of visuospatial attention in patients infected with hepatitis C virus (HCV). Results: Despite endorsing symptoms of impaired concentration and fatigue, IFN-α-treated patients (n = 10) exhibited task performance and activation of parietal and occipital brain regions similar to that seen in HCV-infected control subjects (n = 11). Interestingly, however, in contrast to control subjects, IFN-α-treated patients exhibited significant activation in the dorsal part of the anterior cingulate cortex (ACC), which highly correlated with the number of task-related errors. No such correlation was found in control subjects. Conclusions: Consistent with the role of the ACC in conflict monitoring, ACC activation during IFN-α administration suggests that cytokines might increase processing conflict or reduce the threshold for conflict detection, thereby signaling the need to exert greater mental effort to maintain performance. Such alterations in ACC activity might in turn contribute to cytokine-induced behavioral changes.