title: Cannabis use before age 15 and subsequent executive functioning.
abstract: BACKGROUND
  Many studies have suggested that adolescence is a period of particular vulnerability to neurocognitive effects associated with substance misuse. However, few large studies have measured differences in cognitive performance between chronic cannabis users who started in early adolescence (before age 15) with those who started later.
  
  
  OBJECTIVE
  To examine the executive functioning of individuals who started chronic cannabis use before age 15 compared with those who started chronic cannabis use after 15 and controls.
  
  
  METHODS
  We evaluated the performance of 104 chronic cannabis users (49 early-onset users and 55 late-onset users) and 44 controls who undertook neuropsychological tasks, with a focus on executive functioning. Comparisons involving neuropsychological measures were performed using generalised linear model analysis of variance (ANOVA).
  
  
  RESULTS
  The early-onset group showed significantly poorer performance compared with the controls and the late-onset group on tasks assessing sustained attention, impulse control and executive functioning.
  
  
  CONCLUSIONS
  Early-onset chronic cannabis users exhibited poorer cognitive performance than controls and late-onset users in executive functioning. Chronic cannabis use, when started before age 15, may have more deleterious effects on neurocognitive functioning.
authors.affiliation: Laboratório Interdisciplinar de Neurociências Clínicas and Unidade de Pesquisas em Álcool e Drogas, Departamento de Psiquiatria, Universidade Federal de São Paulo, São Paulo, Brazil. m.alice@plenamente.com.br
authors.forename: Maria Alice
authors.initials: MA
authors.lastname: Fontes
authors.forename: Karen I
authors.initials: KI
authors.lastname: Bolla
authors.forename: Paulo Jannuzzi
authors.initials: PJ
authors.lastname: Cunha
authors.forename: Priscila Previato
authors.initials: PP
authors.lastname: Almeida
authors.forename: Flávia
authors.initials: F
authors.lastname: Jungerman
authors.forename: Ronaldo Ramos
authors.initials: RR
authors.lastname: Laranjeira
authors.forename: Rodrigo A
authors.initials: RA
authors.lastname: Bressan
authors.forename: Acioly L T
authors.initials: AL
authors.lastname: Lacerda
mesh_terms: D000293:Adolescent; D041923:Adolescent Development / Q000187:drug effects*; D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D000704:Analysis of Variance; D001921:Brain / Q000187:drug effects / Q000254:growth & development; D002186:Cannabinoids / Q000008:administration & dosage / Q000009:adverse effects*; D002648:Child; D003072:Cognition Disorders / Q000139:chemically induced* / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004305:Dose-Response Relationship, Drug; D056344:Executive Function / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications* / Q000453:epidemiology; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D002186:Cannabinoids