BACKGROUND Cannabis use is associated with outcomes like income, legal problems, and psychopathology. This finding rests largely on correlational research designs, which rely at best on statistical controls for confounding. Here, we control for unmeasured confounders using a longitudinal study of twins. METHOD In a sample of 4,078 American adult twins first assessed decades ago, we used cotwin control mixed effects models to evaluate the effect of lifetime average frequency of cannabis consumption measured on substance use, psychiatric, and psychosocial outcomes. RESULTS On average, participants had a lifetime cannabis frequency of about one to two times per month, across adolescence and adulthood. As expected, in individual-level analyses, cannabis use was significantly associated with almost all outcomes in the expected directions. However, when comparing each twin to their cotwin, which inherently controls for shared genes and environments, we observed within-pair differences consistent with possible causality in three of the 22 assessed outcomes: cannabis use disorder symptoms (βW-Pooled = .15, SE = .02, p = 1.7 × 10-22), frequency of tobacco use (βW-Pooled = .06, SE = .01, p = 1.2 × 10-5), and illicit drug involvement (βW-Pooled = .06, SE = .02, p = 1.2 × 10-4). Covariate specification curve analyses indicated that within-pair effects on tobacco and illicit drug use, but not cannabis use disorder, attenuated substantially when covarying for lifetime alcohol and tobacco use. CONCLUSIONS The cotwin control results suggest that more frequent cannabis use causes small increases in cannabis use disorder symptoms, approximately 1.3 symptoms when going from a once-a-year use to daily use. For other outcomes, our results are more consistent with familial confounding, at least in this community population of twins. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

中文翻译：

---

终生使用大麻频率对心理和社会影响有限：来自对 4,078 名双胞胎进行的 30 年社区研究的证据。


背景大麻的使用与收入、法律问题和精神病理学等结果相关。这一发现很大程度上依赖于相关研究设计，这些设计最多依赖于混杂的统计控制。在这里，我们通过对双胞胎的纵向研究来控制未测量的混杂因素。方法 在几十年前首次评估的 4,078 名美国成年双胞胎样本中，我们使用 cotwin 控制混合效应模型来评估终生平均大麻消费频率对物质使用、精神和社会心理结果的影响。结果 平均而言，参与者一生中使用大麻的频率约为每月一到两次，从青春期到成年期。正如预期的那样，在个人层面的分析中，大麻的使用与预期方向上的几乎所有结果均显着相关。然而，当将每对双胞胎与他们的 cotwin（本质上控制共享基因和环境）进行比较时，我们观察到配对内差异与 22 个评估结果中的三个可能的因果关系一致：大麻使用障碍症状（βW-Pooled = .15，SE = .02，p = 1.7 × 10-22）、烟草使用频率（βW-Pooled = .06，SE = .01，p = 1.2 × 10-5）以及非法药物参与（βW-Pooled = .06 ，SE = .02，p = 1.2 × 10-4)。协变量规格曲线分析表明，当终生饮酒和烟草使用共变时，对烟草和非法药物使用的配对内效应显着减弱，但大麻使用障碍则不然。结论 cotwin 对照结果表明，更频繁地使用大麻会导致大麻使用障碍症状略有增加，从每年一次使用到每天使用时，大约增加 1.3 个症状。 对于其他结果，我们的结果与家庭混杂因素更加一致，至少在这个社区双胞胎群体中是这样。 （PsycInfo 数据库记录 (c) 2023 APA，保留所有权利）。