Brain Imaging to Understand the Role of Inflammation in N-Acetyl Cysteine (NAC) Treatment of Bipolar Depression

Inclusion Criteria: * Bipolar 2 disorder and meets criteria for a major depressive episode * Age 18-60 * Females of child-bearing potential must be willing to use an acceptable method of birth control throughout the study * Not currently taking psychotropic medications besides those allowed in the clinical trial Exclusion Criteria: * Failed trial or intolerable side effects of NAC * Diagnosis of other major psychiatric disorders such as lifetime schizophrenia, schizoaffective disorder, psychotic features of bipolar disorder, current drug or alcohol abuse or recent drug or alcohol dependence * Significant active physical illness, including blood dyscrasias, lymphomas, hypersplenism, endocrinopathies, renal failure, chronic obstructive lung disease, autonomic neuropathies, peripheral vascular disease. Any disorders with inflammation, malignancy, autoimmune or infectious etiology. Systolic blood pressure \>140 or diastolic blood pressure \> 100 Hemoglobin \<11 in females or \<13 in males * Metal implants, pacemaker, metal prostheses, metal orthodontic appliances or shrapnel in the body * Current, past or anticipated exposure to radiation