Cannabis in the USA is transitioning from a nationwide illegal status to liberalisation for medicinal or recreational use across different jurisdictions. As the acceptability and accessibility of cannabis continue to grow, updated knowledge on the cancer risk from recreational cannabis use is necessary to inform recommendations by public health organisations, policy makers, and clinical practitioners. We reviewed the evidence to date. Our umbrella review of current global epidemiological evidence reveals that links between cannabis exposure and cancer risk are more suggestive than conclusive. The cancer type most closely linked to cannabis use is non-seminoma testicular cancer. However, evidence is emerging of an increased risk of other types of cancer (eg, lung squamous cell carcinoma, head and neck squamous cell carcinoma, and oral, breast, liver, cervical, laryngeal, pancreatic, thyroid, and childhood cancer), underscoring the potential importance of incorporating prevention and cessation of cannabis use in cancer prevention efforts. Our review also identified the need for replication of previous studies for additional epidemiological investigations that use rigorous study designs, and data collection protocols free from the biases of major confounders, misclassification, and measurement error in assessing cannabis exposure. Research on the long-term health and economic consequences of all cannabis products (both medical and recreational) are also needed. Currently, the insufficient evidence on the health risks of cannabis use reduces the ability of policy makers, health-care professionals, and individuals to make informed decisions about cannabis use and could expose the public to a potentially serious health risk.

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美国的癌症风险和大麻合法化：证据概述


美国的大麻正在从全国性的非法状态过渡到不同司法管辖区的医疗或娱乐用途自由化。随着大麻的可接受性和可及性不断提高，有必要更新关于娱乐性使用大麻的癌症风险的知识，以便为公共卫生组织、政策制定者和临床从业者提供建议。我们评价了迄今为止的证据。我们对当前全球流行病学证据的总括性审查表明，大麻暴露与癌症风险之间的联系更多的是提示性的，而不是决定性的。与大麻使用最密切相关的癌症类型是非精原细胞瘤睾丸癌。然而，越来越多的证据表明，其他类型癌症（例如，肺鳞状细胞癌、头颈部鳞状细胞癌以及口腔癌、乳腺癌、肝癌、宫颈癌、喉癌、胰腺癌、甲状腺癌和儿童癌）的风险增加，强调了将预防和停止使用大麻纳入癌症预防工作的潜在重要性。我们的综述还确定了复制先前研究的必要性，以进行额外的流行病学调查，这些调查使用严格的研究设计和数据收集方案，在评估大麻暴露时没有主要混杂因素、错误分类和测量误差的偏差。还需要对所有大麻产品（包括医疗和娱乐）的长期健康和经济影响进行研究。目前，关于大麻使用健康风险的证据不足，降低了政策制定者、医疗保健专业人员和个人对大麻使用做出明智决定的能力，并可能使公众面临潜在的严重健康风险。