Proc Natl Acad Sci U S A. 2012 Oct 2;109(40):E2657-64. doi: 10.1073/pnas.1206820109. Epub 2012 Aug 27.

Persistent cannabis users show neuropsychological decline from childhood to midlife.

Meier MH, Caspi A, Ambler A, Harrington H, Houts R, Keefe RS, McDonald K, Ward A, Poulton R, Moffitt TE.

Source

Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA. madeline.meier@duke.edu

Abstract

Recent reports show that fewer adolescents believe that regular cannabis use is harmful to health. Concomitantly, adolescents are initiating cannabis use at younger ages, and more adolescents are using cannabis on a daily basis. The purpose of the present study was to test the association between persistent cannabis use and neuropsychological decline and determine whether decline is concentrated among adolescent-onset cannabis users. Participants were members of the Dunedin Study, a prospective study of a birth cohort of 1,037 individuals followed from birth (1972/1973) to age 38 y. Cannabis use was ascertained in interviews at ages 18, 21, 26, 32, and 38 y. Neuropsychological testing was conducted at age 13 y, before initiation of cannabis use, and again at age 38 y, after a pattern of persistent cannabis use had developed. Persistent cannabis use was associated with neuropsychological decline broadly across domains of functioning, even after controlling for years of education. Informants also reported noticing more cognitive problems for persistent cannabis users. Impairment was concentrated among adolescent-onset cannabis users, with more persistent use associated with greater decline. Further, cessation of cannabis use did not fully restore neuropsychological functioning among adolescent-onset cannabis users. Findings are suggestive of a neurotoxic effect of cannabis on the adolescent brain and highlight the importance of prevention and policy efforts targeting adolescents.

Comment in

Personality may explain the association between cannabis use and neuropsychological impairment. [Proc Natl Acad Sci U S A. 2013]
Personality may explain the association between cannabis use and neuropsychological impairment.Daly M. Proc Natl Acad Sci U S A. 2013 Mar 12; 110(11):E979. Epub 2013 Mar 4.
Reply to Rogeberg and Daly: No evidence that socioeconomic status or personality differences confound the association between cannabis use and IQ decline. [Proc Natl Acad Sci U S A. 2013]
Reply to Rogeberg and Daly: No evidence that socioeconomic status or personality differences confound the association between cannabis use and IQ decline.Moffitt TE, Meier MH, Caspi A, Poulton R. Proc Natl Acad Sci U S A. 2013 Mar 12; 110(11):E980-2.
Long-term effects of adolescent-onset and persistent use of cannabis. [Proc Natl Acad Sci U S A. 2012]
Long-term effects of adolescent-onset and persistent use of cannabis.Gonzalez R, Swanson JM. Proc Natl Acad Sci U S A. 2012 Oct 2; 109(40):15970-1. Epub 2012 Sep 24.