Study to Evaluate the Efficacy of ALKS 3831 on Body Weight in Young Adults Who Have Been Recently Diagnosed With Schizophrenia, Schizophreniform, or Bipolar I Disorder

Inclusion Criteria:

• Has less than 24 weeks previous treatment with antipsychotics (cumulative; lifetime)
• Subject treated with aripiprazole can receive an additional 1 year of treatmentat ≤5 mg/day, and this treatment will not be considered as part of the 24 weeksof previous treatment with antipsychotics
• Has less than 4 years elapse since the initial onset of active-phase of symptoms
• Has a body mass index (BMI) of <30 kg/m^2
• Agrees to use an acceptable method of contraception for the duration of the study andfor 30 days after the last dose of study drug
• Subject meets the criteria for a primary diagnosis of schizophrenia, schizophreniformdisorder, or bipolar I disorder
• For bipolar I disorder, must have been experiencing an episode of acute mania within ≤14 days prior to Visit 1
• Suitable for outpatient treatment
• Additional criteria may apply

Exclusion Criteria:

• Poses a current suicide risk
• Has a history of poor or inadequate response to treatment with olanzapine
• Has previously been treated with long-acting injectable antipsychotic medicationwithin the 2 months prior to screening, or has > 6 months cumulative life use, or hasreceived treatment with electroconvulsive therapy in their lifetime
• Has initiated treatment with mood stabilizers (eg lithium, valproate, etc) >2 monthsprior to Visit 1
• Has a positive drug screen for opioids, phencyclidine (PCP),amphetamine/methamphetamine, or cocaine
• Has taken opioid agonists (eg, codeine, oxycodone, tramadol, morphine) within the 14days prior to Visit 1, or has taken opioid antagonists, including naltrexone andnaloxone, within 60 days prior to Visit 1
• Taking any weight loss agents or hypoglycemic agents
• Has a clinically significant or unstable medical illness, condition, or disorder thatwould be anticipated to potentially compromise subject safety or adversely affect theevaluation of efficacy
• Has joined a weight management program or had significant changes in diet or exerciseregimen within the past 6 weeks
• Has started a smoking cessation program within the past 6 months
• Has a history of diabetes
• Currently pregnant or breastfeeding or is planning to become pregnant during the studyor within 30 days of the last study drug administration
• Additional criteria may apply