Chunk #3 — Bias in a protocol for a meta-analysis of 5-HTTLPR, stress, and depression — Issue 1: “Primary Analysis Plan 2” to study lifetime depression does not allow for establishing temporal order between stress and depression
Setting aside for the moment the question of temporal order between cause and effect, studies using lifetime measures should not be used because these measures are inaccurate, inadequate, and misleading as measures of depression and stress. The literature contains ample documentation that retrospective recall of lifetime depression is inadequate for research purposes. We reviewed this evidence in Psychological Medicine[6], and since then the inadequacy of retrospective recall of lifetime depression has been demonstrated in multiple studies [7]–[9]. Together these and prior papers show that retrospective lifetime reports overlook at least half of depression cases. Thus Plan 2 of the meta-analysis will wrongly assign many individuals who have had depression to the non-depressed outcome group. Numerous publications have noted that retrospective checklists of lifetime stressful life events are likewise unsuitable for research purposes [10,11]. In relation to the subject of the proposed meta-analysis, GxE research, the poor accuracy of these retrospective recall measures is particularly important. Simulation studies reveal that the difference between measurements that are unreliable (correlation with true score = 0.4) vs reliable (0.7) corresponds to a large difference
