title: Immune system: a possible nexus between cannabinoids and psychosis.
abstract: BACKGROUND
  Endocannabinoid system is involved in the regulation of the brain-immune axis. Cannabis consumption is related with the development, course, and severity of psychosis. The epidemiological evidence for increased occurrence of immunological alterations in patients with psychosis has not been sufficiently addressed. The aim of this review is to establish whether there is any scientific evidence of the influence of cannabinoids on aspects of immunity that affect susceptibility to psychotic disorder induction.
  
  
  METHODS
  A comprehensive search of PubMed/MEDLINE, EMBASE and ISI Web of Knowledge was performed using combinations of key terms distributed into three blocks: "immune", "cannabinoid", and "endocannabinoid receptor". Studies were considered to be eligible for the review if they were original articles, they reported a quantitative or qualitative relation between cannabinoid ligands, their receptors, and immune system, and they were carried out in vitro or in mammals, included humans. All the information was systematically extracted and evaluated.
  
  
  RESULTS
  We identified 122 articles from 446 references. Overall, endocannabinoids enhanced immune response, whereas exogenous cannabinoids had immunosuppressant effects. A general change in the immune response from Th1 to Th2 was also demonstrated for cannabinoid action. Endogenous and synthetic cannabinoids also modulated microglia function and neurotransmitter secretion.
  
  
  CONCLUSIONS
  The actions of cannabinoids through the immune system are quite regular and predictable in the peripheral but remain fuzzy in the central nervous system. Despite this uncertainty, it may be hypothesized that exposure to exocannabinoids, in particular during adolescence might prompt immunological dysfunctions that potentially cause a latent vulnerability to psychosis. Further investigations are warranted to clarify the relationship between the immunological effects of cannabis and psychosis.
authors: University Hospital Marqués de Valdecilla, Department of Psychiatry, School of Medicine, University of Cantabria, Santander, Spain; CIBERSAM, Biomedical Research Network on Mental Health Area, Madrid, Spain; IDIVAL, Valdecilla Biomedical Research Institute, Santander, Spain. Electronic address: p.suarez.pinilla@gmail.com.
authors: Paula
authors: P
authors: Suárez-Pinilla
authors: University Hospital Marqués de Valdecilla, Department of Psychiatry, School of Medicine, University of Cantabria, Santander, Spain.
authors: José
authors: J
authors: López-Gil
authors: University Hospital Marqués de Valdecilla, Department of Psychiatry, School of Medicine, University of Cantabria, Santander, Spain; CIBERSAM, Biomedical Research Network on Mental Health Area, Madrid, Spain; IDIVAL, Valdecilla Biomedical Research Institute, Santander, Spain.
authors: Benedicto
authors: B
authors: Crespo-Facorro
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology; D063385:Cannabinoid Receptor Modulators / Q000494:pharmacology; D002186:Cannabinoids / Q000378:metabolism* / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D063388:Endocannabinoids / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D007249:Inflammation; D007962:Leukocytes / Q000276:immunology; D011605:Psychoses, Substance-Induced / Q000276:immunology*; D011618:Psychotic Disorders / Q000209:etiology / Q000276:immunology; D012559:Schizophrenia / Q000209:etiology / Q000235:genetics / Q000276:immunology*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology
chemical_list: D063385:Cannabinoid Receptor Modulators; D002186:Cannabinoids; D016207:Cytokines; D063388:Endocannabinoids
keywords: Cytokines; Endocannabinoid system; First-episode psychosis; Immunology; Infection; Microglia; Schizophrenia; Δ(9)THC