一项研究报告说,近期一项研究所报告的在青春期开始使用大麻与智商下降之间的正关联有可能用社会经济地位对智商造成的混杂的影响加以解释。Ole Rogeberg使用一个模拟模型评估了社会经济地位对智商的潜在影响,结果发现这种混杂因素足以重现智商变化和接触大麻之间的联系,而该联系是由此前新西兰达尼丁(Dunedin)的一个大规模群组研究所报告的。此前发表的基于同一个达尼丁群组的论文指出,早期开始使用大麻的情况在具有某些风险因素的人群中更常见,这些风险因素与社会经济地位低有相关性。此外,此前的研究提示有类似的智商但是社会经济地位不同的儿童自选或者被选入了对认知有不同要求的环境,而这反过来又导致了他们智商的分化。这位作者提出,得出接触大麻和智商下降之间的因果推论可能为时尚早,而且对达尼丁群组的进一步分析可能有助于区分有竞争性的解释。这位作者说,根据智商变化是否由于大麻造成的永久性神经毒性损伤,或者智商变化是否由于不同的认知环境造成的其他非永久性效应,其所带来的政策意义可能不同。(生物谷Bioon.com)
doi: 10.1073/pnas.1215678110
PMC:
PMID:
Correlations between cannabis use and IQ change in the Dunedin cohort are consistent with confounding from socioeconomic status
Ole Rogeberg1
Does cannabis use have substantial and permanent effects on neuropsychological functioning? Renewed and intense attention to the issue has followed recent research on the Dunedin cohort, which found a positive association between, on the one hand, adolescent-onset cannabis use and dependence and, on the other hand, a decline in IQ from childhood to adulthood [Meier et al. (2012) Proc Natl Acad Sci USA 109(40):E2657–E2664]. The association is given a causal interpretation by the authors, but existing research suggests an alternative confounding model based on time-varying effects of socioeconomic status on IQ. A simulation of the confounding model reproduces the reported associations from the Dunedin cohort, suggesting that the causal effects estimated in Meier et al. are likely to be overestimates, and that the true effect could be zero. Further analyses of the Dunedin cohort are proposed to distinguish between the competing interpretations. Although it would be too strong to say that the results have been discredited, the methodology is flawed and the causal inference drawn from the results premature.