Abstract: Methods and compositions for preventing or reducing weight gain and associated metabolic syndrome in patients receiving atypical antipsychotic drugs for treatment of mental illnesses are described. The invention comprises administering to a patient in need of treatment an effective amount of a dopamine agonist in conjunction with an effective amount of an atypical antipsyochotic drug. In one embodiment of the invention, the dopamine agonist is pramipexole. The dopamine agonist may be administered in a low dose, such as less than 1 mg per day of pramipexole. Examples of atypical antipsychotic drugs which may be administered in conjunction with the dopamine agonist include clozapine, olanzapine, quetiapine and risperadone.