Middeldorp C M, Cath D C, Beem A L, Willemsen G, Boomsma D I
Department of Biological Psychology, Vrije Universiteit, Van der Boechorststraat 1, Amsterdam, The Netherlands.
Psychol Med. 2008 Nov;38(11):1557-65. doi: 10.1017/S0033291708002985. Epub 2008 Feb 25.
The association between life events and anxious depression might be due to causality or to gene-environment correlation. We examined unidirectional and reciprocal causality and a gene-environment correlation model, in which genes that influence the vulnerability for anxious depression also increase the risk of exposure to life events. The effect of genes that influence environmental exposure might be mediated through personality and we therefore also examined the association between life events and personality (neuroticism and extraversion).
Information on life events, anxious depression, neuroticism and extraversion was collected in 5782 monozygotic (MZ) and dizygotic (DZ) twins who participated in a longitudinal survey study of the Netherlands Twin Register. To examine causality, data were analysed longitudinally. To examine gene-environment correlation, the co-twin control method was used.
Anxious depression and, to a lesser extent, neuroticism scores increased after exposure to life events. Anxious depression and neuroticism also predicted the experience of life events. Prospectively, extraversion was not associated with life events. Anxious depression, neuroticism and extraversion scores did not differ between the non-exposed subjects of MZ and DZ twin pairs and unrelated subjects discordant for life events.
Our findings suggest that reciprocal causation explains the relationship between life events and anxious depression and between life events and neuroticism. Extraversion is not related to life events. No evidence was found for gene-environment correlation, i.e. the genes that influence anxious depression, neuroticism or extraversion do not overlap with the genes that increase the risk of exposure to life events.
生活事件与焦虑性抑郁之间的关联可能是因果关系所致，也可能是基因 - 环境相关性导致。我们研究了单向和双向因果关系以及一种基因 - 环境相关模型，在该模型中，影响焦虑性抑郁易感性的基因也会增加遭遇生活事件的风险。影响环境暴露的基因效应可能通过人格来介导，因此我们还研究了生活事件与人格（神经质和外向性）之间的关联。
在参与荷兰双胞胎登记纵向调查研究的5782对同卵（MZ）和异卵（DZ）双胞胎中收集了有关生活事件、焦虑性抑郁、神经质和外向性的信息。为了研究因果关系，对数据进行了纵向分析。为了研究基因 - 环境相关性，使用了同卵双胞胎对照方法。
暴露于生活事件后，焦虑性抑郁以及程度较轻的神经质得分增加。焦虑性抑郁和神经质也预测了生活事件的发生。前瞻性地看，外向性与生活事件无关。MZ和DZ双胞胎对中未暴露的个体以及生活事件不一致的无关个体之间，焦虑性抑郁、神经质和外向性得分没有差异。
我们的研究结果表明，双向因果关系解释了生活事件与焦虑性抑郁之间以及生活事件与神经质之间的关系。外向性与生活事件无关。未发现基因 - 环境相关性的证据，即影响焦虑性抑郁、神经质或外向性的基因与增加遭遇生活事件风险的基因不重叠。
