In this trial, fifty participants with current major depressive disorder who are not receiving an antidepressant medication and fifty healthy controls will complete questionnaires and computerized tasks to assess their decision-making styles. There will be three visits for depressed patients and two for healthy controls (the first and third visits). The first visit will involve interviews and questionnaires to assess the participant's level of depression, medical history and quality of life. Participants will then complete the decision-making tasks, and will earn between $5-40 based on their choices, in order to make the decisions on the computer tasks financially meaningful. At the completion of this visit, depressed patients will be prescribed an FDA-approved antidepressant, chosen in consultation with the treating psychiatrist. Patients will be responsible for paying for the prescription themselves. After two weeks on the medication, the patient will be seen for a follow-up visit to ensure tolerability of the medicine. After six weeks on the medicine, patients and healthy controls will return to repeat the questionnaires and the computer based decision-making tasks, and will again earn between $5-40 based on their performance.

During episodes of depression patients with major depressive disorder (MDD) may make sub-optimal decisions based on exaggerated negative beliefs about themselves, the future, or the world around them. These disruptions in decision-making contribute adversely to quality of life, in both work and personal realms. Although effective treatments for depression are available, very little work has explored the effects of treatment on how people make decisions. The specific aspects of decision-making that differ between depressed and health control individuals are unknown, and whether any changes in these decision-making features occur as a result of improvement from depression, or whether medication treatment itself can lead to changes in decision-making, even in the absence of clinical improvement.

In this trial, fifty participants with current major depressive disorder who are not receiving an antidepressant medication and fifty healthy controls will complete questionnaires and computerized tasks to assess their decision-making styles. There will be three visits for depressed patients and two for healthy controls (the first and third visits). The first visit will involve interviews and questionnaires to assess the participant's level of depression, medical history and quality of life. Participants will then complete the decision-making tasks, and will earn between $5-40 based on their choices, in order to make the decisions on the computer tasks financially meaningful. At the completion of this visit, depressed patients will be prescribed an FDA-approved antidepressant, chosen in consultation with the treating psychiatrist. Patients will be responsible for paying for the prescription themselves. After two weeks on the medication, the patient will be seen for a follow-up visit to ensure tolerability of the medicine. After six weeks on the medicine, patients and healthy controls will return to repeat the questionnaires and the computer based decision-making tasks, and will again earn between $5-40 based on their performance.

The overall goal of this study will be to identify whether decision-making characteristics in people with major depression is affected by treatment, and whether depressed patients make decisions differently from healthy controls. A total of 4 decision-making tasks and one control task will be administered via computer to eligible subjects. The specific tasks are:

1. Risk Task - This task assesses tolerance of risk by having participants decide whether they wish to accept a specific dollar payout, or to play a lottery with an uncertain payout.
2. Balloon Analogue Risk Task - The participant is presented with a balloon and offered the chance to earn money by pumping the balloon up by clicking a button. Each click causes the balloon to incrementally inflate and money to be added to a counter up until some threshold, at which point the balloon is over inflated and explodes. Thus, each pump confers greater risk but also greater potential reward. If the participant chooses to cash-out prior to the balloon exploding then they collect the money earned for that trial, but if balloon explodes earnings for that trial are lost. Participants are not informed about the balloons breakpoints; the absence of this information allows for testing both participants' initial responses to the task and changes in responding as they gain experience with the task contingencies.
3. Temporal Discounting Task - Participants are initially asked to choose between taking an immediate reward now or a larger reward at some time in the future. Decisions for seven time points over a 10-year time frame are proposed. The task is then repeated using choices between immediate and delayed losses, based on the same seven time points. This task assesses the manner in which subjects value immediate outcomes compared to long-term consequences.
4. Ultimatum Game - The ultimatum game (UG) is a well-established game-theoretical paradigm commonly employed in behavioral economics to measure emotional reactions to unfair offers. In the UG, two subjects sequentially exchange real monetary amounts. Specifically, a proposer is provided with a sum of money by the experimenter ($10), and asked to share this amount of money with another player, the responder. The responder then decides whether to accept or reject the offer made by the proposer. If the responder accepts the offer, both players receive the respective amounts from the proposer's offer. If she rejects the offer made by the proposer, both players receive nothing ($0). This is best illustrated via the following two potential scenarios: 1. the proposer offers a fair split of $5 for himself and $5 for the responder. This is an offer that is typically accepted by a great majority of responders. 2. The proposer offers a split of $9 for himself and $1 for the responder. Such offers are commonly rejected by the majority of responders, despite incurring a financial loss of $1.
5. Continuous Performance Task - This task involves identifying patterns of numbers briefly displayed on a computer screen. This task will serve as a control variable for attention in analyzing the results of the decision-making tasks.

Inclusion Criteria for MDD Subjects:

1. Male or female, age 18-65
2. Primary Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV TR) Diagnosis of Major Depressive Disorder.
3. Has a 17-item Hamilton depression rating scale (HDRS-17) score >=16.
4. Ability to visually read and understand English language
5. Not currently taking an antidepressant.
6. Women of reproductive potential must be willing to take a medically approved form of birth control throughout the duration of the study.

Inclusion Criteria for Healthy Control Subjects:

1. Male or female, age 18-65
2. No current DSM-IV TR diagnosis of a mental illness.
3. No lifetime history of Major Depressive Disorder or Dysthymia.
4. Has a 17-item Hamilton depression rating scale (HDRS-17) score ≤7.
5. Ability to visually read and understand English language
6. Not currently taking any psychoactive medication

Exclusion Criteria for all subjects:

1. Has met criteria at any time during their life for bipolar disorder, a primary psychotic disorder (e.g. schizophrenia), or dementia.
2. Meet criteria for substance abuse or dependence within three months of the screening visit.
3. Presents with a clinically significant suicide risk, as assessed by a study physician.
4. Presence of any unstable or central nervous system-related medical illness that would interfere with cognition or participation.
5. Women who are currently pregnant or lactating, or plan to become pregnant during the study.

All participants who consented to take part in the study and fulfilled all eligibility criteria are included in the baseline analysis.

Adverse events were collected from the time each participant provided informed consent throughout the entire 6 week duration of study participation.