Two days ago, two doctors attended a conference in the industry, at which a doctor presented a case – a patient with depression improved after taking medication, and recently discovered hepatitis C virus infection, and was given interferon injection treatment, depressive symptoms reappeared. Should I continue to use it?” . Another specialist said, “The incidence of depression in people using interferon is more than 30%, so it is recommended to continue with another manufacturer if possible”. My consideration is: is interferon the only factor that causes depression, if not, it will affect and mislead the treatment. It is true that this data is “real”, and a more reasonable study would be to divide the treated population with hepatitis C virus infection into two groups: one treated with interferon and one control group, and finally to see if there is a significant correlation between the two groups in terms of the incidence of depression. But in reality it is not possible, every patient is treated aggressively, interferon is almost always the most effective treatment for viral infection, and no one wants to give up this method.