Nitric oxide involvement in depression during interferon-alpha therapy.
It has been postulated that interferon induces depression via a nitric oxide-related system. The purpose of this study was to test whether there was a difference in the effects of interferon-alpha (IFN-alpha) on nitric oxide production between patients with and without interferon-induced depression. The subjects had chronic hepatitis C and were being treated with IFN-alpha. We measured plasma nitrate, a marker of nitric oxide production in vivo, before, during, and after interferon therapy. Of 146 patients, 9 developed depression within the first 4 wk of interferon therapy, and 8 developed depression later. In the former group, a significant plasma nitrate increase was observed during therapy, followed by a decrease to baseline after discontinuation. This, however, was not the case with the latter group or those who had no psychiatric symptoms. These results suggest nitric oxide involvement in at least some forms of IFN-alpha-induced depression.