This study will last 12 weeks. Participants will be randomly assigned to receive either 250 mg Depakote or placebo. The dose of medication will increase at the end of Week 1 to 500 mg of either depakote or placebo; participants will remain on this dose through Week 5. At Week 6, participants will cross-over and receive the other treatment (either depakote or placebo), which they will take through Week 12. Study visits will occur weekly and will include a physical exam, blood and urine tests, and self-reports of adverse events. In addition, caregivers will complete reports about mood swings throughout the study.