The purpose of this study is to compare weight gain in patients taking ALKS 3831 versus patients taking only olanzapine.

After a screening period of up to 4 weeks, if you are enrolled into the study, you will visit the clinic twice in the first 2 weeks, then every other week for a further 14 weeks. If you agree to participate, you must be willing and able to visit the clinic for the entire study. You may start the study as an inpatient if the study doctor thinks you will likely be able to change to outpatient treatment within 2 weeks after starting the study drug.