Patient description: A 26-year-old obese woman with a history of bipolar disorder complains that her recent struggles with her weight and eating have caused her to feel depressed. She states that she has recently had difficulty sleeping and feels excessively anxious and agitated. She also states that she has had thoughts of suicide. She often finds herself fidgety and unable to sit still for extended periods of time. Her family tells her that she is increasingly irritable. Her current medications include lithium carbonate and zolpidem.

Clinical trial eligibility criteria: eligible ages (years): 8.0-19.0,  Psychotic Disorders DSM diagnoses that have an FDA indication for atypical antipsychotic use for at least one agent in the respective pediatric or adult age group. Specifically, primary DSM-IV diagnosis of Early Onset Schizophrenia Spectrum (EOSS; schizophrenia, schizoaffective disorder, schizophreniform disorder, psychotic disorder NOS); Bipolar Spectrum (bipolar I, II and NOS); Major depressive disorder with psychosis; Mood disorder NOS corresponding to Leibenluft and colleagues severely mood dysregulated (SMD) broad spectrum bipolar disorder; Mood disorder NOS corresponding to irritability associated with autism spectrum disorders; or for adult teen participants aged 18-19 years Major depressive disorder. Diagnoses will be determined by clinical interview, Leibenluft's modification of the K-SADS-PL, and the "Aberrant Behavior Checklist" (cutoff score of 18, as used by FDA for approval of risperidone and aripiprazole in minors) Clinically stable on current treatment regimen for at least 30 days, as assessed in a three-step process Current SGA treatment with olanzapine, quetiapine, risperidone, ziprasidone aripiprazole, asenapine, iloperidone, lurasidone, paliperidone, or olanzapine/fluoxetine for ≥ 8 weeks Stable dose of current SGA and psychotropic co-medications for at least 30 days Body mass index (BMI) at least in the 85th percentile for age and gender Substantial weight gain over the previous 3 years while taking a SGA, as reflected by family and referring physician's judgment. The weight gain did not have to occur on the child's current SGA. Weight needs to have remained stable or increased over past year Agrees to use two effective forms of birth control or to remain abstinent Has a primary caretaker who has known the child well for at least 6 months before study entry  Treatment with any medication (other than the currently prescribed psychotropic medications) that would significantly alter glucose, insulin, or lipid levels. Exception: orlistat and amantadine are permitted if the individual has taken the drug for at least one year without weight loss Major neurological or medical illness that affects weight gain or that would prevent participation in physical activities Fasting glucose levels indicating need for prompt treatment Pediatrician or pediatric gastroenterologist recommendation to address abnormal fasting labs by pursuing more active treatment than those in the 2007 American Medical Association guidelines Diagnosis of anorexia nervosa or bulimia nervosa, as based on current or lifetime DSM-IV Diagnosis of substance dependence disorder (other than tobacco dependence) within the past month, as based on DSM-IV Positive urine toxicology indicating ongoing use of illicit substance Current treatment with more than one antipsychotic medication Current treatment with more than 3 total psychotropic medications (i.e., 2 psychotropics plus SGA), with the exception of subjects taking 2 medications for ADHD in which a total of 4 psychotropic medications are allowed Known hypersensitivity to metformin