title: Association of Stimulant Use With Dopaminergic Alterations in Users of Cocaine, Amphetamine, or Methamphetamine: A Systematic Review and Meta-analysis.
abstract: Stimulant use disorder is common, affecting between 0.3% and 1.1% of the population, and costs more than $85 billion per year globally. There are no licensed treatments to date. Several lines of evidence implicate the dopamine system in the pathogenesis of substance use disorder. Therefore, understanding the nature of dopamine dysfunction seen in stimulant users has the potential to aid the development of new therapeutics.
  
  
  
  To comprehensively review the in vivo imaging evidence for dopaminergic alterations in stimulant (cocaine, amphetamine, or methamphetamine) abuse or dependence.
  
  
  
  The entire PubMed, EMBASE, and PsycINFO databases were searched for studies from inception date to May 14, 2016.
  
  
  
  Case-control studies were identified that compared dopaminergic measures between stimulant users and healthy controls using positron emission tomography or single-photon emission computed tomography to measure striatal dopamine synthesis or release or to assess dopamine transporter availability or dopamine receptor availability.
  
  
  
  Demographic, clinical, and imaging measures were extracted from each study, and meta-analyses and sensitivity analyses were conducted for stimulants combined, as well as for cocaine and for amphetamine and methamphetamine separately if there were sufficient studies.
  
  
  
  Differences were measured in dopamine release (assessed using change in the D2/D3 receptor availability after administration of amphetamine or methylphenidate), dopamine transporter availability, and dopamine receptor availability in cocaine users, amphetamine and methamphetamine users, and healthy controls.
  
  
  
  A total of 31 studies that compared dopaminergic measures between 519 stimulant users and 512 healthy controls were included in the final analysis. In most of the studies, the duration of abstinence varied from 5 days to 3 weeks. There was a significant decrease in striatal dopamine release in stimulant users compared with healthy controls: the effect size was -0.84 (95% CI, -1.08 to -0.60; P < .001) for stimulants combined and -0.87 (95% CI, -1.15 to -0.60; P < .001) for cocaine. In addition, there was a significant decrease in dopamine transporter availability: the effect size was -0.91 (95% CI, -1.50 to -0.32; P < .01) for stimulants combined and -1.47 (95% CI, -1.83 to -1.10; P < .001) for amphetamine and methamphetamine. There was also a significant decrease in D2/D3 receptor availability: the effect size was -0.76 (95% CI, -0.92 to -0.60; P < .001) for stimulants combined, -0.73 (95% CI, -0.94 to -0.53; P < .001) for cocaine, and -0.81 (95% CI, -1.12 to -0.49; P < .001) for amphetamine and methamphetamine. Consistent alterations were not found in vesicular monoamine transporter, dopamine synthesis, or D1 receptor studies.
  
  
  
  Data suggest that both presynaptic and postsynaptic aspects of the dopamine system in the striatum are down-regulated in stimulant users. The commonality and differences between these findings and the discrepancies with the preclinical literature and models of drug addiction are discussed, as well as their implications for future drug development.
authors.affiliation: Psychiatric Imaging Group, Medical Research Council London Institute of Medical Sciences Centre, London, England2Psychiatric Imaging Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, England3Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, England.
authors.forename: Abhishekh H
authors.initials: AH
authors.lastname: Ashok
authors.affiliation: Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, England4Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Yuya
authors.initials: Y
authors.lastname: Mizuno
authors.affiliation: National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland6National Institute on Drug Abuse, Bethesda, Maryland.
authors.forename: Nora D
authors.initials: ND
authors.lastname: Volkow
authors.affiliation: Psychiatric Imaging Group, Medical Research Council London Institute of Medical Sciences Centre, London, England2Psychiatric Imaging Group, Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, England3Department of Psychosis Studies, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, England.
authors.forename: Oliver D
authors.initials: OD
authors.lastname: Howes
mesh_terms: D019969:Amphetamine-Related Disorders / Q000378:metabolism*; D019970:Cocaine-Related Disorders / Q000378:metabolism*; D003342:Corpus Striatum / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D006801:Humans; D011954:Receptors, Dopamine / Q000378:metabolism*
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D011954:Receptors, Dopamine; D004298:Dopamine