This study will compare two different antidepressant treatment regimens to determine which is more effective in reducing symptoms of bipolar depression.

Depression is a serious condition that is often difficult to diagnosis and treat. Bipolar disorder-related depression is especially complex because of the presence of mania symptoms. Lamotrigine and divalproex are commonly prescribed medications for depression. However, their effectiveness in treating bipolar depression has not been thoroughly evaluated. Studies have shown that combining lamotrigine with another antidepressant may be more effective in reducing depressive symptoms than lamotrigine alone. This study will provide participants with either lamotrigine alone or in combination with divalproex and will determine which regimen is more effective in reducing symptoms of bipolar depression.

Participants will be randomly assigned to a daily regimen of either lamotrigine and divalproex or lamotrigine and placebo for 8 months. Participants will be assessed at study entry, at two unspecified times during the study, and at the end of the study. During each assessment, participants will undergo a brief interview and complete a questionnaire about their depressive symptoms, any physical manifestations of their depression, and their overall level of functioning in daily activities.

Inclusion Criteria:

• Diagnosis of bipolar disorder I or II
• Experiencing symptoms of depression at study entry OR have experienced symptoms of depression within 6 months prior to study entry
• Willing to use acceptable methods of contraception
• Parent or guardian willing to provide informed consent, if applicable

Exclusion Criteria:

• History of liver disease
• History of substance abuse
• Previous treatment with lamotrigine or divalproex
• Lamotrigine or divalproex intolerance