Psychological and behavioural effects of interferons

Immunotherapy with interferons may induce neuropsychiatric symptoms and disorders. Interferon-α-based immunotherapy is used to treat patients with chronic hepatitis C and metastatic renal cell carcinoma. Immunotherapy with interferon-α induces symptoms such as slowness, severe fatigue, hypersomnia, lethargy, depressed mood, mnemonic troubles, irritability, short temper, emotional lability, social withdrawal, lack of concentration and full blown major depression in a considerable number of patients treated. The exact mechanism whereby interferon-α induces depression has remained elusive. However, there is now some evidence that interferon-α-based immunotherapy induces the cytokine network, decreases the serotonergic turnover in the brain, and induces the catabolism of tryptophan. There is evidence that interferon-α immunotherapy-induced depression is related to an increased catabolism of tryptophan into kynurenine.