Importance Cannabis use and potency of cannabis have increased during the past 2 decades. If the association between cannabis use and schizophrenia is causal, this should be reflected in an increase in the proportion of cases of schizophrenia being attributable to cannabis, the population-attributable risk fraction (PARF). Objective To determine whether the PARF for cannabis use disorder in schizophrenia has increased over time. Design, Setting, and Participants This nationwide, register-based historical prospective cohort study included all people in Denmark born before December 31, 2000, who were alive and 16 years or older at some point from January 1, 1972, to December 31, 2016. Data analysis was performed from August 2020 to April 2021. Exposure Diagnosis of cannabis use disorder. Main Outcomes and Measures Diagnosis of schizophrenia, with estimated PARF of cannabis use disorder in schizophrenia from 1972 to 2016. Results A total of 7 186 834 individuals were included in the analysis, including 3 595 910 women (50.0%) and 3 590 924 men (50.0%). The adjusted hazard ratio for schizophrenia fluctuated at approximately 4 (with 95% CIs ranging from approximately 3 to 6) throughout most of the study period when people diagnosed with cannabis use disorder were compared with those without cannabis use disorder. The PARF of cannabis use disorder in schizophrenia also fluctuated, but with clear evidence of an increase from 1995 (when the PARF was relatively stable around 2.0%, with a 95% CI of approximately 0.3% to either side) until reaching some stability around 6.0% to 8.0% (with a 95% CI of approximately 0.5% to either side) since 2010. Conclusions and Relevance The results from these longitudinal analyses show the proportion of cases of schizophrenia associated with cannabis use disorder has increased 3- to 4-fold during the past 2 decades, which is expected given previously described increases in the use and potency of cannabis. This finding has important ramifications regarding legalization and control of use of cannabis.

中文翻译：

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丹麦精神分裂症中大麻使用障碍的人群归因风险分数随时间推移的发展。

在过去的 2 年里，大麻的使用和大麻的效力有所增加。如果大麻使用与精神分裂症之间存在因果关系，这应反映在可归因于大麻的精神分裂症病例比例的增加上，即人群归因风险分数 (PARF)。目的 确定精神分裂症中大麻使用障碍的 PARF 是否随着时间的推移而增加。设计、地点和参与者 这项全国性的、基于登记的历史前瞻性队列研究包括所有在 2000 年 12 月 31 日之前出生的丹麦人，他们在 1972 年 1 月 1 日至 2016 年 12 月 31 日期间的某个时间点活着且 16 岁或以上. 数据分析时间为 2020 年 8 月至 2021 年 4 月。 大麻使用障碍的暴露诊断。主要结果和措施精神分裂症的诊断，估计 1972 年至 2016 年精神分裂症中大麻使用障碍的 PARF。 结果共有 7 186 834 人被纳入分析，其中包括 3 595 910 名女性（50.0%）和 3 590 924 名男性（50.0%）。在研究期间的大部分时间里，当将被诊断患有大麻使用障碍的人与没有大麻使用障碍的人进行比较时，精神分裂症的调整后风险比在大约 4 上下波动（95% CI 范围从大约 3 到 6）。精神分裂症中大麻使用障碍的 PARF 也有波动，但有明确的证据表明从 1995 年（当时 PARF 相对稳定在 2.0% 左右，95% CI 左右为 0.3%）直到达到某种稳定在 6.0 左右自 2010 年以来 % 至 8.0%（95% CI 左右两侧约为 0.5%）。结论和相关性 这些纵向分析的结果显示，在过去 20 年中，与大麻使用障碍相关的精神分裂症病例比例增加了 3 至 4 倍，鉴于之前描述的大麻使用和效力的增加，这是可以预期的。这一发现对大麻使用的合法化和控制产生了重要影响。