Lengthy television viewing in adolescence may raise the risk for depression in young adulthood, according to a new report. The study, in the February issue of The Archives of General Psychiatry, published by the American Medical Association, found a rising risk of depressive symptoms with increasing hours spent watching television. Researchers used data from a larger analysis of 4,142 adolescents who were not depressed at the start of the study. After seven years of follow-up, more than 7 percent had symptoms of depression. But while about 6 percent of those who watched less than three hours a day were depressed, more than 17 percent of those who watched more than nine hours a day had depressive symptoms. ...
The word 'raise' in the title implies cause-and-effect, not just association. When comparing lengthy viewers with those who watch less, what possible confounders can you think of? Provide a possible confounder and your reasoning for this.
Using the confounder from your answer in (a), draw a pathway graph depicting the possible relationship between confounder, possible cause and outcome. Given the limits of the keyboard, do the best you can.