title: Cannabis use and cognitive function in first episode psychosis: differential effect of heavy use.
abstract: BACKGROUND
  First episode patients and patients with schizophrenia exhibit increased rates of cannabis use compared to the general population. Contrary to what has been reported in studies with healthy people, most of the published studies so far have reported no impairments or even beneficial effects on neurocognition associated with cannabis consumption in psychotic patients. However, these studies did not address the effects of very high cannabis consumption.
  
  
  OBJECTIVE
  Our aim in this study was to assess the effects on neurocognition of medium and heavy cannabis consumption in first psychotic episode patients.
  
  
  METHODS
  A total of 74 patients were included in the study and assigned to three different groups according to their mean cannabis consumption during the last year (non-users, medium users, and heavy users). Participants were administered verbal memory and other neurocognitive tasks.
  
  
  RESULTS
  Heavy cannabis users were significantly impaired in all the verbal memory measures with respect to non-users, including immediate (p = .026), short-term (p = .005), and long-term (p = .002) memory. There were no significant differences between medium and non-users. Moreover, non-users performed better than all cannabis users in the arithmetic task (p = .020). Heavy cannabis consumption was associated with more commission errors in the continuous performance task (CPT) (p = .008) and more time to complete trail making test A (TMT-A) (p = .008), compared to the group of medium users.
  
  
  CONCLUSIONS
  Heavy cannabis consumption seems to impair verbal memory in first psychotic episode patients. Heavy users also perform worse than medium users in other neurocognitive tasks. Based on the results and the available evidence, a dose-related effect of cannabis consumption is suggested.
authors.affiliation: Parc Sanitari Sant Joan de Déu, Sant Boi de Llobregat, Spain. c.nunez@pssjd.org.|Universitat de Barcelona, Barcelona, Spain. c.nunez@pssjd.org.
authors.forename: Christian
authors.initials: C
authors.lastname: Núñez
authors.affiliation: Parc Sanitari Sant Joan de Déu, Sant Boi de Llobregat, Spain.|Instituto de Salud Carlos III, Centro de Investigación en Red de Salud Mental (CIBERSAM), Madrid, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Ochoa
authors.affiliation: Parc Sanitari Sant Joan de Déu, Sant Boi de Llobregat, Spain.|Instituto de Salud Carlos III, Centro de Investigación en Red de Salud Mental (CIBERSAM), Madrid, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Huerta-Ramos
authors.affiliation: Parc Sanitari Sant Joan de Déu, Sant Boi de Llobregat, Spain.|Instituto de Salud Carlos III, Centro de Investigación en Red de Salud Mental (CIBERSAM), Madrid, Spain.
authors.forename: Iris
authors.initials: I
authors.lastname: Baños
authors.affiliation: Research Unit, Centre d'Higiene Mental Les Corts, Barcelona, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Barajas
authors.affiliation: Instituto de Salud Carlos III, Centro de Investigación en Red de Salud Mental (CIBERSAM), Madrid, Spain.|Psychiatry Department, Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain.
authors.forename: Montserrat
authors.initials: M
authors.lastname: Dolz
authors.affiliation: Psychiatry Department, Hospital Sant Joan de Déu, Esplugues de Llobregat, Spain.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Sánchez
authors.affiliation: Parc Sanitari Sant Joan de Déu, Sant Boi de Llobregat, Spain.
authors.forename: Núria
authors.initials: N
authors.lastname: Del Cacho
authors.affiliation: Parc Sanitari Sant Joan de Déu, Sant Boi de Llobregat, Spain.|Instituto de Salud Carlos III, Centro de Investigación en Red de Salud Mental (CIBERSAM), Madrid, Spain.
authors.forename: Judith
authors.initials: J
authors.lastname: Usall
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001288:Attention / Q000187:drug effects; D002648:Child; D003071:Cognition / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D056344:Executive Function / Q000187:drug effects; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications / Q000523:psychology*; D008433:Mathematics; D008569:Memory Disorders / Q000139:chemically induced / Q000523:psychology; D008570:Memory, Short-Term / Q000187:drug effects; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance / Q000187:drug effects; D012559:Schizophrenia / Q000150:complications; D012565:Schizophrenic Psychology; D055815:Young Adult
keywords: Cannabis; First psychotic episode; Memory; Neurocognition; Psychosis