PET and MRI Brain Imaging of Bipolar Disorder

PET and MRI imaging will be used to investigate the aims described above in patients who have bipolar disorder or unipolar depression and are currently experiencing a depressive episode. Both healthy controls and depressed participants with bipolar disorder or unipolar depression will be recruited. Patients who are on medication before enrolling in the study will have a three week washout. At baseline, healthy controls and patients will have an MRI consisting of both structural and functional sequences. Psychological measures will also be obtained at baseline. Within one week of the MRI, both patients and healthy controls will have one CUMI and one DASB PET scan. Following the baseline PET scans, patient participants will begin medication treatment with either lithium or lamotrigine, based on the clinical judgement of the treating psychiatrist. Psychological measures will be obtained every 2 weeks. After 6 weeks of medication treatment at a therapeutic dose, patients will be assessed for remission (defined as a 50% decrease in the HDRS score from baseline). If this criteria is met, patient participants will then have follow-up PET scans (one CUMI and one DASB). If this criteria is not met, the patient will be switched to the other medication under study and will be reevaluated after an additional 4 weeks of medication treatment. Patients who still do not demonstrate a 50% decrease in their HDRS will be considered non-responders and will have repeat CUMI and DASB scans.