As well as suffering from delusions and hallucinations people with schizophrenia often experience so-called negative symptoms such as flat mood, lack of interest in being sociable and an inability to experience pleasure, as well as many cognitive problems. Psychiatrists often prescribe antidepressants for these symptoms but there are reports of negative effects as well as positive ones. Researchers from the University of Wolverhampton reviewed 23 studies into the use of antidepressants for people with psychosis. They found a moderate positive effect from the antidepressants and significant responses for the drugs fluoxetine, trazodone and ritanserin.
Singh, Surendra P., Singh, Vidhi and Chan, Kelvin - Efficacy of antidepressants in treating the negative symptoms of chronic schizophrenia: meta-analysis British Journal of Psychiatry September 2010, 197(3), 174-179