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Psychiatry Res. 2015 Dec 30;230(3):878-84. doi: 10.1016/j.psychres.2015.11.033. Epub 2015 Nov 25.

Evaluating the relationship between cannabis use and IQ in youth and young adults at clinical high risk of psychosis.

Author information

1
Department of Psychiatry, University of Calgary, Calgary, Alberta, Canada.
2
Department of Psychiatry, Harvard Medical School at Beth Israel Deaconess Medical Center, Boston, MA, United States.
3
Department of Psychiatry, UCSD, La Jolla, CA, United States.
4
Department of Psychology, Yale University, New Haven, CT, United States.
5
Department of Psychiatry, Zucker Hillside Hospital, Long Island, NY, United States.
6
Department of Psychiatry, Yale University, New Haven, CT, United States.
7
Department of Psychiatry, University of North Carolina, Chapel Hill, NC, United States; Massachusetts General Hospital, Boston, MA, United States.
8
Departments of Psychology and Psychiatry, Emory University, Atlanta, GA, United States.
9
Departments of Psychiatry and Biobehavioral Sciences and Psychology, UCLA, Los Angeles, CA, United States.
10
University of California, San Francisco, CA, United States.
11
Department of Psychiatry, University of Calgary, Calgary, Alberta, Canada. Electronic address: jmadding@ucalgary.ca.

Abstract

Among people with psychosis, those with a history of cannabis use show better cognitive performance than those who are cannabis naïve. It is unknown whether this pattern is present in youth at clinical high risk (CHR) of psychosis. We evaluated relationships between IQ and cannabis use while controlling for use of other substances known to impact cognition in 678 CHR and 263 healthy control (HC) participants. IQ was estimated using the Vocabulary and Block Design subtests of the Wechsler Abbreviated Scale of Intelligence. Drug and alcohol use severity and frequency were assessed with the Alcohol and Drug Use Scale, and we inquired participants' age at first use. CHR were further separated into early and late age at onset of cannabis use sub-groups, and low-, moderate- and high-frequency sub-groups. No significant differences in IQ emerged between CHR or HC cannabis users vs. non-users, or between use frequency groups. CHR late-onset users showed significantly higher IQ than CHR early-onset users. Age at onset of cannabis use was significantly and positively correlated with IQ in CHR only. Results suggest that age at onset of cannabis may be a more important factor for IQ than use current use or use frequency in CHR.

KEYWORDS:

Age at onset; Alcohol; Cannabis; IQ; Prodrome; Schizophrenia

PMID:
26626949
PMCID:
PMC5037441
DOI:
10.1016/j.psychres.2015.11.033
[Indexed for MEDLINE]
Free PMC Article

Conflict of interest statement

All authors declare no conflict of interest.

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