Treating Depression: A Randomized Clinical TrialBackground

Clinical depression is a recurrent illness requiring treatment and often hospitalization. Nearly 50% of people who have an episode of major depression will have a recurrence within 2-3 years. Being able to prevent the recurrence of depression in people who are at risk for the disease would go a long way to alleviate the pain and suffering of patients and would also save society many thousands of dollars in medical expenses and lost wages due to an inability to work.

The Study

During the 1980's the federal government, through the National Institutes of Health (NIH), sponsored a multi-centered, randomized, controlled, clinical trial to evaluate two drugs to prevent the recurrence of depression in patients who have had at least one previous episode of the illness (Prien et al., Archives of General Psychiatry, 1984).

The Study Design

The study was multi-centered. There were 5 medical clinics in major metropolitan areas across the United States that participated in this trial. Using many clinics enabled the investigators to enroll many more patients into the study and allowed for more diversity in the patients who participated. There were 3 treatment groups. Patients received either Imipramine (Imip), Lithium (Li), or a Placebo (Pl) where Imip and Li are active drugs. Patients were randomly assigned to one of the 3 treatment groups. Like most other medical studies where new, unexplored treatments are evaluated, patients chose themselves to participate in the study by signing a consent form. Patients were followed for 2-4 years to see whether or not they had a recurrence of depression. If they did not have a recurrence within this time frame, then their treatment was considered a "success". If they did have a recurrence, it was considered a "Failure." The study was double-blinded. A number of additional background variables were measured for each patient.

Variables

AcuteT The number of days the patient had been depressed before the current study started

Treat L=Lithium; I=Imipramine; P=Placebo

Outcome S=Success F=Failure (depression returns)

The Data

Here is the data collected from the study: https://docs.google.com/spreadsheets/d/1HvPIb_WwzAl161cPXYQ7XeZh-DSBWP-zw1kYEhlze24/edit#gid=1048140601

Part 1

1. Describe the population of interest (include where, when, and what type of people were studied)?
2. Describe the sample (include how large and where they were found)?
3. Which variables are categorical (AcuteT, Treatment,Outcome)?
4. What parameter is the researcher interested in studying (Hint: "Mean of ...." OR "Percentage of ...."?)
5. Is this an observational study or an experiment? Explain how you know.
6. What are the explanatory and response variables?
7. List 3 other variables the researcher might want to record on each individual suffering from depression.