• INCLUSION CRITERIA:

Two groups of subjects will be recruited for studies under this protocol: unipolar depressives and bipolar depressives. Subjects with unipolar or bipolar depression appear to exhibit abnormal cholinergic function during the depressed phase, and no differences are hypothesized to exist between MDD and BD depressives herein. However, while BD subjects are more difficult to recruit, the evidence for cholinergic abnormalities has been particularly compelling for BD. Moreover, observations from our pilot study suggest that scopolamine will improve symptoms in both MDD and BD, a particularly persuasive observation given BD notoriously has been difficult to treat. Thus, the magnitude of this serious clinical problem justifies the inclusion of BD subjects. Therefore both groups will be recruited. However, BD Type I subjects will be included only if they are currently stable on lithium or valproate to reduce the risks associated with possible precipitation of mania.

The presence of inclusion and exclusion criteria will be established using both an unstructured clinical interview with a psychiatrist and the Structured Clinical Interview for DSM-IV (SCID). Family history of mental illness will be obtained from the subject using the Family Interview of Genetic Studies. We will recruit 24 subjects per group.

DEPRESSED SAMPLES: Subjects (ages 18-55) currently suffering from a major depressive episode falling into one of the following subgroups:

1. . MAJOR DEPRESSIVE DISORDER (MDD): Subjects will be selected with primary MDD and are currently depressed as defined by DSM-IV criteria for recurrent MDD and current MADRS score in the moderately-to-severely depressed range (greater than or equal to 20). The duration of the index episode is greater than or equal to four weeks.
2. . BIPOLAR DISORDER TYPE II (BD): Subjects will be selected who meet DSM-IV criteria for bipolar disorder Type I or II and are currently depressed, with MADRS score in the moderately-to-severely depressed range (greater than or equal to 20). The duration of the index episode is greater than or equal to four weeks.

EXCLUSION CRITERIA:

Subjects will be recruited who are drug-naive or who have not received psychotropic drugs for at least 3 weeks (8 weeks for fluoxetine) prior to screening. Subjects also will be excluded if they have: a) serious suicidal ideation or behavior, or current delusions or hallucinations, b) inability to provide informed consent, c) serious, unstable illnesses including hepatic, renal, gastroenterologic, respiratory, cardiovascular (including ischemic heart disease, endocrinologic, neurologic, immunologic, or hematologic disease, d) a history of drug or alcohol abuse within 6 months or alcohol or drug dependence in the last five years (DSM IV criteria), e) not using a medically accepted means of contraception and are a woman of childbearing potential, f) current pregnancy (documented by pregnancy testing), g) current breast feeding, h) history of ulcerative colitis or toxic megacolon, i) vision and/or hearing problems severe enough to interfere with testing, j) electrocardiographic evidence of ischemia, arrhythmia, conduction defect, or myocardial infarction, k) current blood pressure of greater than 160 mm Hg or less than 90 mm Hg systolic, or greater than 90 mm Hg diastolic, l) clinically significant cerebrovascular or cardiovascular disease, hypertension, congestive heart disease, angina pectoris, clinic evidence of cerebrovascular disease, gross neurological impairment, hyperthyroidism, known hypersensitivity or idiosyncracy to anticholinergic agents (e.g. skin rashes), glaucoma, renal or hepatic impairment, m) current nicotine use or nicotine dependence within last six months (due to the effects of nicotine on the cholinergic system) n) narrow angle glaucoma (due to the possibility of exacerbation of this condition by scopolamine) o) age greater than 50 years (to reduce the biological heterogeneity encompassed by the MDD and BD criteria, since subjects with a late age-at onset for depression have a far greater likelihood of having MRI correlates of cerebrovascular disease than age-matched, healthy controls or age-matched, early-onset depressives), p) exposure within two weeks to medications likely to affect mood or cognition or likely to interact with scopolamine (e.g. narcotics or anti-cholinergic agents)- as verified by history and urine drug screen, q) HIV positive status, r) history of gastric or intestinal obstructions, s) history of urinary retention or bladder obstruction. During the course of this study, participants will be unable to take some medications, including antidepressant or antianxiety agents, sleep aids, diphenhydramine (e.g. Benedryl) or cough/cold preparations that contain diphenhydramine or antihistamines. A detailed list of allowed and not allowed medications is provided in Appendix B in the protocol.

We are not excluding comorbid anxiety disorders. Exclusion of patients with comorbid anxiety disorders would affect the generalizability of our findings since a substantial percentage of patients with major depression have these comorbid diagnoses. Instead, we will exclude patients with this comorbid diagnosis only if it is believed to be of clinical significance. Allowing participation by patients with histories of comorbid anxiety disorders broadens the inclusion criteria to more closely approximate patients seen in real world settings.