2. Timing of measurements . Brown and Harris [19] noted that studies that have failed to replicate the GxE between 5-HTTLPR variation and life events have measured the occurrence of stressful life events in the months immediately preceding the depressive outcomes [19]. In contrast, most of the positive replications have been in keeping with the original study by Caspi and colleagues in measuring life events in the five years prior to the outcome. Retrospective recall of adversity over long periods of time may increase the risk of forgetting or discounting of events [30] or lead to a bias due to selective recall when those who are depressed self report [27,31]. When only a lifetime diagnosis of depression is available, information about relative timing of stressors and depression is lost.
