Answer the following questions using the circles below, which represent three potential causal structures for depression.
- a. What type of cause does each circle represent?
- b. What type of cause are “lack of physical activity” and “lack of social support” in circle 1?
- c. What type of cause is “genetics” in circles 1, 2, and 3?
- d. In circle 1, if lack of social support is the exposure of interest, what are genetics, lack of physical activity, and the unknown causes?
- e. Imagine that everyone with depression in the population was represented by circle 2, but in the U.S. 75% of people had a gene for depression, while in Canada 30% of people have that gene. In which setting would the effect of social support appear stronger?
- f. If you could intervene to block the gene for depression (assume such a gene exists), what effect would you expect to see on the rate of depression in this population?
Source: Aschengrau and Seage
