Dopamine Neurotransmission in Major Depression

Inclusion Criteria:

- Both genders and all ethnic origins, age between 18 and 45;

- Written informed consent;

- Right-handed (Chapman and Chapman 1987);

- Absence of serious or unstable medical illness, including cardiovascular, hepatic,
renal, respiratory, endocrine, neurologic or hematologic disease;

- Absence of history of seizure disorder;

- Absence of history of current diagnosis of any of the following DSM-IV psychiatric
illnesses: organic mental disorder, schizophrenia, schizoaffective disorder,
delusional disorder, psychotic disorders not otherwise specified, bipolar
disorder, patients with mood congruent or mood incongruent psychotic features,
substance dependence, substance abuse within the last 12 months (with the
exception of cocaine or stimulant abuse; which will lead to exclusion), as assessed
by subject history and a structured clinical interview (SCID-I/NP);

- Absence of history of cocaine or stimulant use (e.g., amphetamine, cocaine,
methamphetamine);

- Absence of history of use of dopaminergic drugs (including methylphenidate);

- Absence of current use of other psychotropic drugs

- Absence of substance dependence or substance abuse in the last 12 months;

- Absence of history or current diagnosis of dementia, or a score greater than 26 on
the Mini Mental Status Examination (Folstein, 1975) at the screening visit;

- Absence of clinical or laboratory evidence of hypothyroidism;

- Absence of neurological illness

Specific exclusion criteria for PET scan are as follows:

- Pregnant women, women trying to get pregnant, or women of childbearing potential who
are not using a medically accepted means of contraception (defined as implant,
condom, diaphragm, spermicide, IUD, s/p tubal ligation, partner with vasectomy).

- Failure to meet standard PET safety requirements.

Specific inclusion criteria for depressed participants are as follows:

- DSM-IV diagnostic criteria for MDD melancholia subtype (diagnosed with the use of the
SCID) or MDD with anhedonia (score of 3 or greater on the Snaith-Hamilton Pleasure
Scale (SHPS));

- A baseline HRSD score (Hamilton 1960) greater than or equal to 16 (17-item version);

- Absence of suicidal ideation where outpatient treatment is determined unsafe by the
study clinician. These patients will be immediately referred to appropriate clinical
treatment;

- Absence of past or current mood congruent or incongruent psychotic features;

- Absence of lifetime history of electroconvulsive therapy (ECT)

- Subjects taking antidepressants at the time of their screening visit will be enrolled
only if they are willing (after discussing with their prescribing clinician), and the
study clinician determines that it is clinically appropriate for them to discontinue
their current antidepressant for a period greater than five half-lives of their
current medication (but no longer than 7 days). For these subjects, the baseline
visit and the first physiology session will only occur after the 7 day interval has
passed.

Specific inclusion criteria for control participants are as follows:

- Absence of any psychiatric illness (including alcohol and substance abuse), as
assessed by subject history and a structured clinical interview (SCID-I/NP).

- Absence of any medication for at least three weeks.