proband’s friends and relatives. 2) Some studies assess stress through currently depressed individuals’ self-reports, which are biased by mood-congruent memory revision and thus overcount events (13). Moreover, humans seek explanations, a phenomenon termed “effort after meaning,” which leads respondents who have been depressed to misattribute their illness to a life event. Some studies assess events through long-term retrospective reports (sometimes over decades), which are flawed by forgetting and undercount life events, particularly among respondents who lack depression. In addition, respondents often overcount trivial and undercount severe events (9). These cognitive processes (mood-congruent memory revision, effort after meaning, and retrospective forgetting) working together can artifactually influence a study’s association between life events and depression. Thus, a correlation between life events and depression does not indicate validity, contrary to claims (14). 3) Some studies test the connection between stress and depression contemporaneously, others across years or decades. 4) Some studies are unable to rule out reverse causation, in which depression precipitates stressful events; for example, one study measured depression over the respondents’ lifetime, but ascertained life stress during only the past year (15). 5) Most studies do not consider variation in participants’ depression history, despite evidence that stress is more relevant for
