Giuffra L A, Risch N
Department of Psychiatry, Washington University School of Medicine, Jewish Hospital of St Louis, MO 63110.
Psychol Med. 1994 May;24(2):375-83. doi: 10.1017/s0033291700027355.
Several large-scale epidemiological surveys have reported increasing lifetime rates of psychopathology among recently born cohorts. In the case of Major Depressive Disorder (MDD) younger cohorts tend to manifest higher lifetime prevalences of the condition than older cohorts, at any given age. In some studies, cohort differences are so large that the youngest cohort exceeds the lifetime prevalence of the oldest cohort well before passing through their total period of risk. The data on lifetime prevalences that support the existence of secular differences, however, has typically been collected in cross-sectional studies. Thus, individuals are interviewed at a single point in time and asked to recall all prior psychopathology. Due to poor recall, this design may greatly underestimate earlier experiences. In fact, cohort differences are not limited to MDD; similar results have been reported for a wide range of psychopathology, suggesting methodological problems at data collection. We have conducted a simulation study to examine the magnitude of annual rates of forgetting that could produce the secular trends reported for MDD. Small, but constant annual rates produce striking, 'cohort effect-like' curves. The rates needed to reconstruct the reported effect are compatible with published values for test-retest studies of lifetime recall of MDD. This simulation study does not rule out the existence of a cohort effect in some psychiatric disorders, but stresses the possible limitations of using cross-sectional studies to investigate secular trends.
几项大规模的流行病学调查显示，在最近出生的人群中，精神病理学的终生患病率呈上升趋势。就重度抑郁症（MDD）而言，在任何给定年龄，较年轻的人群往往比年长者表现出更高的终生患病率。在一些研究中，人群差异非常大，以至于最年轻的人群在尚未度过整个风险期之前，其终生患病率就超过了最年长者。然而，支持长期差异存在的终生患病率数据通常是在横断面研究中收集的。因此，在某个时间点对个体进行访谈，并要求他们回忆所有先前的精神病理学情况。由于回忆不佳，这种设计可能会大大低估早期经历。事实上，人群差异并不局限于MDD；对于广泛的精神病理学情况也有类似的结果报道，这表明在数据收集方面存在方法学问题。我们进行了一项模拟研究，以检验可能导致MDD报告的长期趋势的年度遗忘率的大小。微小但恒定的年度遗忘率会产生显著的“类似队列效应”曲线。重建报告效应所需的遗忘率与已发表的关于MDD终生回忆的重测研究值相符。这项模拟研究并不排除某些精神疾病中存在队列效应，但强调了使用横断面研究来调查长期趋势可能存在的局限性。
