Andrade Chittaranjan
Department of Psychopharmacology, National Institute of Mental Health and Neurosciences, Bangalore, India.
J Clin Psychiatry. 2016 Jun;77(6):e739-42. doi: 10.4088/JCP.16f10918.
Psychosis is one of the most serious among the adverse effects associated with cannabis use. The association between cannabis use and psychosis has been variously explored in a series of recent meta-analyses. The results of these meta-analyses show that persons who develop psychosis experience onset of psychosis about 2-3 years earlier if they are cannabis users; this effect is not observed with alcohol or other substance use. Higher levels of cannabis use are associated with greater risk of psychosis. Current cannabis abuse or dependence (but not past use or lower levels of current use) increases the risk of transition into psychosis in persons at ultrahigh risk of psychosis. About a third of patients with first-episode psychosis are cannabis users, and, at follow-up, about half of these users are found to continue their cannabis use. Continued cannabis use (in those who are treated after developing psychosis) is associated with higher risk of relapse into psychosis, and discontinuation of cannabis use reduces the risk of relapse to that in cannabis nonusers. Finally, persons with psychosis who continue to use cannabis have more severe positive symptoms and poorer levels of functioning. Because experimental studies in humans show that cannabinoids and cannabis can induce psychotic symptoms, it is reasonable to assume that the epidemiologic data indicate a causal effect of cannabis in anticipating, triggering, or exacerbating psychosis in vulnerable individuals and in worsening the course and outcome of the illness in those who continue to use the substance. Given the public health implications of these findings, the trend to legalize medical marijuana must be viewed with concern, and efforts are necessary to educate patients and the public about the serious mental and physical health risks associated with cannabis use and abuse.
精神病是与使用大麻相关的最严重的不良反应之一。近期一系列的荟萃分析对大麻使用与精神病之间的关联进行了多方面的探究。这些荟萃分析的结果表明，患精神病的人如果是大麻使用者，其精神病发作时间要比非使用者早大约2至3年；而酒精或其他物质的使用则未观察到这种效应。大麻使用量越高，患精神病的风险就越大。当前存在大麻滥用或依赖（而非过去使用或当前较低的使用水平）会增加超高风险精神病患者转变为精神病的风险。约三分之一的首发精神病患者是大麻使用者，在随访中，发现这些使用者中约有一半继续使用大麻。持续使用大麻（在患精神病后接受治疗的患者中）与精神病复发的较高风险相关，而停止使用大麻可将复发风险降低至非使用者的水平。最后，继续使用大麻的精神病患者有更严重的阳性症状且功能水平更差。由于人体实验研究表明大麻素和大麻可诱发精神病症状，因此有理由认为流行病学数据表明大麻在易感个体中引发、触发或加剧精神病以及在继续使用该物质的患者中恶化疾病进程和结果方面具有因果效应。鉴于这些发现对公共卫生的影响，必须对医用大麻合法化的趋势予以关注，并且有必要努力教育患者和公众了解与大麻使用和滥用相关的严重身心健康风险。
