People with major depression sometimes develop psychosis (delusions and hallucinations) as well. Studies have shown that between 15-20% of people with major depression are affected in this way. Major depression with psychosis is associated with poorer short-term outcomes, a longer time to recovery, greater residual disability and greater mortality. A study by 259 people with major depression and psychosis by researchers working on the STOP-PD (study of pharmacotherapy of psychotic depression) project looked into the effectiveness of the combination of the antipsychotic drug olanzapine and the antidepressant sertraline compared to olanzapine on its own. They found that both drugs together led to a greater rate of remission (41.9% vs 23.9%) than olanzapine on its own. The side effects (including weight gain) were broadly similar between the two groups.
Meyers, Barnett S. ... [et al] - A double-blind randomized controlled trial of olanzapine plus sertraline vs olanzapine plus placebo for psychotic depression Archives of General Psychiatry August 2009, 66(8), 838-847