TY - JOUR
T1 - Cannabis use and earlier onset of psychosis
T2 - A systematic meta-analysis
AU - Large, Matthew
AU - Sharma, Swapnil
AU - Compton, Michael T.
AU - Slade, Tim
AU - Nielssen, Olav
PY - 2011/6
Y1 - 2011/6
N2 - Context: A number of studies have found that the use of cannabis and other psychoactive substances is associated with an earlier onset of psychotic illness. Objective: To establish the extent to which use of cannabis, alcohol, and other psychoactive substances affects the age at onset of psychosis by meta-analysis. Data Sources: Peer-reviewed publications in English reporting age at onset of psychotic illness in substance-using and non-substance-using groups were located using searches of CINAHL, EMBASE, MEDLINE, PsycINFO, and ISI Web of Science. Study Selection: Studies in English comparing the age at onset of psychosis in cohorts of patients who use substances with age at onset of psychosis in non-substance-using patients. The searches yielded 443 articles, from which 83 studies met the inclusion criteria. Data Extraction: Information on study design, study population, and effect size were extracted independently by 2 of us. Data Synthesis: Meta-analysis found that the age at onset of psychosis for cannabis users was 2.70 years younger (standardized mean difference=-0.414) than for nonusers; for those with broadly defined substance use, the age at onset of psychosis was 2.00 years younger (standardized mean difference=-0.315) than for nonusers. Alcohol use was not associated with a significantly earlier age at onset of psychosis. Differences in the proportion of cannabis users in the substance-using group made a significant contribution to the heterogeneity in the effect sizes between studies, confirming an association between cannabis use and earlier mean age at onset of psychotic illness. Conclusions: The results of meta-analysis provide evidence for a relationship between cannabis use and earlier onset of psychotic illness, and they support the hypothesis that cannabis use plays a causal role in the development of psychosis in some patients. The results suggest the need for renewed warnings about the potentially harmful effects of cannabis.
AB - Context: A number of studies have found that the use of cannabis and other psychoactive substances is associated with an earlier onset of psychotic illness. Objective: To establish the extent to which use of cannabis, alcohol, and other psychoactive substances affects the age at onset of psychosis by meta-analysis. Data Sources: Peer-reviewed publications in English reporting age at onset of psychotic illness in substance-using and non-substance-using groups were located using searches of CINAHL, EMBASE, MEDLINE, PsycINFO, and ISI Web of Science. Study Selection: Studies in English comparing the age at onset of psychosis in cohorts of patients who use substances with age at onset of psychosis in non-substance-using patients. The searches yielded 443 articles, from which 83 studies met the inclusion criteria. Data Extraction: Information on study design, study population, and effect size were extracted independently by 2 of us. Data Synthesis: Meta-analysis found that the age at onset of psychosis for cannabis users was 2.70 years younger (standardized mean difference=-0.414) than for nonusers; for those with broadly defined substance use, the age at onset of psychosis was 2.00 years younger (standardized mean difference=-0.315) than for nonusers. Alcohol use was not associated with a significantly earlier age at onset of psychosis. Differences in the proportion of cannabis users in the substance-using group made a significant contribution to the heterogeneity in the effect sizes between studies, confirming an association between cannabis use and earlier mean age at onset of psychotic illness. Conclusions: The results of meta-analysis provide evidence for a relationship between cannabis use and earlier onset of psychotic illness, and they support the hypothesis that cannabis use plays a causal role in the development of psychosis in some patients. The results suggest the need for renewed warnings about the potentially harmful effects of cannabis.
UR - http://www.scopus.com/inward/record.url?scp=79956120635&partnerID=8YFLogxK
U2 - 10.1001/archgenpsychiatry.2011.5
DO - 10.1001/archgenpsychiatry.2011.5
M3 - Article
C2 - 21300939
AN - SCOPUS:79956120635
SN - 0003-990X
VL - 68
SP - 555
EP - 561
JO - Archives of General Psychiatry
JF - Archives of General Psychiatry
IS - 6
ER -