National Drug and Alcohol Research Centre, University of New South Wales, NSW 2052, Australia.
Int J Drug Policy. 2010 Jan;21(1):10-9. doi: 10.1016/j.drugpo.2009.09.001. Epub 2009 Sep 26.
Over the past five years, the release of cohort studies assessing the link between cannabis and psychosis has increased attention on this relationship. Existing reviews generally conclude that these cohort studies show cannabis has a causal relationship to psychosis, or at least that one cannot be excluded. Few studies have evaluated the relative strengths and limitations of these methodologically heterogeneous cohort studies, and how their relative merits and weaknesses might influence the way the link between cannabis use and psychosis is interpreted. This paper reviews the methodological strengths and limitations of major cohort studies which have looked at the link between cannabis and psychosis, and considers research findings against criteria for causal inference. Cohort studies that assessed the link between cannabis and psychosis were identified through literature searches using relevant search terms and MEDline, PsycINFO and EMBASE. Reference lists of reviews and key studies were hand searched. Only prospective studies of general population cohorts were included. Findings were synthesised narratively. A total of 10 key studies from seven general population cohorts were identified by the search. Limitations were evident in the measurement of psychosis, consideration of the short-term effects of cannabis intoxication, control of potential confounders and the measurement of drug use during the follow-up period. Pre-existing vulnerability to psychosis emerged as an important factor that influences the link between cannabis use and psychosis. Whilst the criteria for causal association between cannabis and psychosis are supported by the studies reviewed, the contentious issue of whether cannabis use can cause serious psychotic disorders that would not otherwise have occurred cannot be answered from the existing data. Further methodologically robust cohort research is proposed and the implications of how evidence informs policy in the case of uncertainty is discussed.
在过去的五年中，评估大麻与精神病之间关联的队列研究不断增加，这引起了人们对这种关系的关注。现有综述通常得出的结论是，这些队列研究表明大麻与精神病之间存在因果关系，或者至少不能排除这种关系。很少有研究评估这些方法学上异质的队列研究的相对优势和局限性，以及它们的相对优缺点可能如何影响对大麻使用与精神病之间关联的解释。本文综述了评估大麻与精神病之间关联的主要队列研究的方法学优势和局限性，并根据因果推断的标准考虑了研究结果。通过使用相关搜索词和 MEDline、PsycINFO 和 EMBASE 进行文献检索，确定了评估大麻与精神病之间关联的队列研究。综述和关键研究的参考文献列表进行了手工检索。仅纳入了评估一般人群队列中大麻与精神病之间关联的前瞻性研究。研究结果以叙述性方式进行综合。通过检索共确定了来自七个一般人群队列的 10 项关键研究。在精神病的测量、考虑大麻中毒的短期效应、潜在混杂因素的控制以及随访期间药物使用的测量方面存在局限性。精神病的预先存在的易感性被认为是影响大麻使用与精神病之间关联的一个重要因素。虽然研究综述支持大麻与精神病之间因果关联的标准，但不能从现有数据回答大麻使用是否会导致本来不会发生的严重精神病障碍的争议性问题。建议进一步进行方法学上稳健的队列研究，并讨论在不确定情况下证据如何为政策提供信息的影响。
