This article presents a prospective study of 71 patients infected with chronic viral hepatitis C and treated with interferon alpha during one year. The objective was to assess the incidence and predictive factors of anxiety and depression symptoms during and after the therapy. Each patient received psychiatric assessment before, during and after treatment, with evaluations using Hamilton-anxiety and MADRS scales. Results confirm the great incidence of depression and anxiety not only during interferon alpha therapy but also after treatment is discontinued. Sleep disorders and MADRS ratings of M4 seem to be predictive of the therapy's side effects. Thus, there seem to be easily discernable parameters allowing depression and suicidal behaviour to be anticipated. This paper emphasises their possible occurrence after the treatment and, therefore, the need for routine assessments after treatment is discontinued. Teams comprising both hepatologists and psychiatrists should complete these assessments. This shows the necessity of interdisciplinary collaboration treatment of this kind.