, new research showed.
Investigators at the University of Toronto, The Centre for Addiction and Mental Health (CAMH), and the Institute for Clinical Evaluative Sciences (ICES), in Canada, linked recent population-based survey data from more than 11,000 youngsters to health service use records, including hospitalizations, emergency department (ED) visits, and outpatient visits.
“We found a very strong association between cannabis use and risk of psychotic disorder in adolescence [although] surprisingly, we didn’t find evidence of association in young adulthood,” lead author André J. McDonald, PhD, currently a postdoctoral fellow at the Peter Boris Centre for Addictions Research and the Michael G. DeGroote Centre for Medicinal Cannabis Research, McMaster University, Hamilton, Ontario, Canada, said in a news release.
“These findings are consistent with the neurodevelopmental theory that teens are especially vulnerable to the effects of cannabis,” said Dr. McDonald, who conducted the research.
The study was published online in Psychological Medicine.
Increased Potency
“Epidemiologic research suggests that cannabis use may be a significant risk factor for psychotic disorders,” the authors wrote. However, methodological limitations of previous studies make it difficult to estimate the strength of association, with the current evidence base relying largely on cannabis use during the twentieth century, when the drug was “significantly less potent.” It’s plausible that the strength of association has increased due to increased cannabis potency.
The researchers believe youth cannabis use and psychotic disorders is “a critical public health issue,” especially as more jurisdictions liberalize cannabis use and the perception of harm declines among youth.
To estimate the association between cannabis use during youth and the risk for a psychotic disorder diagnosis, using recent population-based data, they used data from the 2009-2012 cycles of the Canadian Community Health Survey (CCHS) linked to administrative health data at ICES to study noninstitutionalized Ontario residents, aged 12-24 years, who had completed the CCHS during that period.
They excluded respondents who used health services for psychotic disorders during the 6 years prior to their CCHS interview date.
Respondents (n = 11,363; 51% men; mean age [SD], 18.3 [15.2-21.3] years) were followed for 6-9 years, with days to first hospitalization, ED visit, or outpatient visit related to a psychotic disorder as the primary outcome.
The researchers estimated age-specific hazard ratios during adolescence (12-19 years) and young adulthood (20-33 years) and conducted sensitivity analyses to explore alternative model conditions, including restricting the outcome to hospitalizations and ED visits, to increase specificity.
Compared with no cannabis use, cannabis use was significantly associated with an 11-fold increased risk for psychotic disorders during adolescence, although not during young adulthood (adjusted hazard ratio [aHR], 11.2; 95% CI, 4.6-27.3 and aHR, 1.3; 95% CI, 0.6-2.6, respectively).
Perception of Harm Declining
When the researchers restricted the outcome to hospitalizations and ED visits only, the strength of association “increased markedly” during adolescence, with a 26-fold higher association in cannabis users than in nonusers (aHR, 26.7; 95% CI, 7.7-92.8). However, there was no meaningful change during young adulthood (aHR, 1.8; 95% CI, 0.6-5.4).