Supplementary Material for: A Biopsychosocial Model of Interferon-Alpha-Induced Depression in Patients with Chronic Hepatitis C Infection

<b><i>Background:</i></b> The aim of this prospective study was to gain a more comprehensive picture of the biopsychosocial effects of interferon-α (IFN-α) treatment of patients with chronic hepatitis C (HCV). The predictors of depressive development and changes in health-related quality of life, life satisfaction and cognitive ability were measured with the inclusion of the social context. Furthermore, the effects of IFN-α treatment on indoleamine 2,3-dioxygenase, the level of tryptophan supply in the brain, the development of neurotoxic kynurenine metabolites and the thyroid glands were investigated. Therefore, for the first time the conditions for the development of depressive episodes in HCV patients treated with IFN-α were examined over the entire period of treatment as well as 3 months later, applying a holistic biopsychosocial model. <b><i>Method:</i></b> Psychiatric and biological assessments were carried out at 6 different times: before, during (at 1, 3, 6 and 9 months) and after the end of IFN-α treatment. <b><i>Results:</i></b> During IFN-α treatment 22 (53.7%) of 41 patients fulfilled the criteria for a treatment-related depressive disorder at least once during treatment. Contributing factors are tryptophan depletion (tryptophan to competing amino acids quotient), increased neurotoxic challenge (kynurenine to kynurenic acid quotient), less social support, female gender, preexisting psychiatric vulnerability, means of transmission, low financial security, impaired sexual satisfaction, small circle of friends, impaired physical role, strong body pain, low general health and vitality, reduced social functioning, impaired mental health and impaired emotional role. <b><i>Conclusions:</i></b> The awareness of relevant risk factors of IFN-α treatment-induced depression is essential to develop preventative treatment strategies.