Gao Bipolar Spectrum Lithium/Quetiapine Study

Inclusion Criteria: * Able to provide informed consent before beginning any study-specific procedures * Male and female patients at least 18 years of age * Meets Diagnostic and Statistical Manual -IV criteria for BPI, BP II, or National Comorbidity Survey-R criteria for sub-threshold BP with or without symptoms, in need of medication adjustment(s) * Willing to be randomized to either Lithium or Quetiapine * If a sexually active female of childbearing potential, be using a reliable method of contraception, such as oral contraceptive or long-term injectable or implantable hormonal contraceptive, double-barrier methods (e.g. condom and diaphragm, condom and foam, condom and sponge), intrauterine devices, and tubal ligation * Women with reproductive potential must have a negative urine pregnancy test Exclusion Criteria: * Unwilling to comply with study requirements * Patients who have had severe adverse reaction to Lithium or Quetiapine * Patients who require inpatient care * Drug/alcohol dependence requiring immediate acute detoxification * Pregnancy as determined by serum pregnancy test or breastfeeding * History of nonresponse to Lithium at doses \>900 mg ≥8 wks or to Quetiapine at doses of at least 300 mg/d ≥ 8 week for depression and at least 400-600 mg/d ≥ 4 wks for mania.