 Schizophrenia is one of the most severe mental illnesses. The antipsychotic drugs, introduced in early 1950s, have revolutionized the treatment of schizophrenia. About 2 to 4 times as many patients relapse when treated with a placebo as do those treated with antipsychotic drugs. For these medications to be maximally beneficial, they must have an acceptable side effect profile and be taken as prescribed. One untoward effect of many antipsychotic drugs is weight gain. The extent of weight gain apparently varies by drug, which may be because of drugsdiffering degrees of action on serotonergic, dopaminergic, histaminergic, and other neurotransmitter systems. Obesity is a threat to health and longevity. Weight gain may also cause patients taking antipsychotic medication to discontinue their medication, which may predispose them to relapse. 