title: Impulsivity and opioid drugs: differential effects of heroin, methadone and prescribed analgesic medication.
abstract: BACKGROUND
  Previous studies have provided inconsistent evidence that chronic exposure to opioid drugs, including heroin and methadone, may be associated with impairments in executive neuropsychological functioning, specifically cognitive impulsivity. Further, it remains unclear how such impairments may relate of the nature, level and extent of opioid exposure, the presence and severity of opioid dependence, and hazardous behaviours such as injecting.
  
  
  METHODS
  Participants with histories of illicit heroin use (n = 24), former heroin users stabilized on prescribed methadone (methadone maintenance treatment; MMT) (n = 29), licit opioid prescriptions for chronic pain without history of abuse or dependence (n = 28) and healthy controls (n = 28) were recruited and tested on a task battery that included measures of cognitive impulsivity (Cambridge Gambling Task, CGT), motor impulsivity (Affective Go/NoGo, AGN) and non-planning impulsivity (Stockings of Cambridge, SOC).
  
  
  RESULTS
  Illicit heroin users showed increased motor impulsivity and impaired strategic planning. Additionally, they placed higher bets earlier and risked more on the CGT. Stable MMT participants deliberated longer and placed higher bets earlier on the CGT, but did not risk more. Chronic opioid exposed pain participants did not differ from healthy controls on any measures on any tasks. The identified impairments did not appear to be associated specifically with histories of intravenous drug use, nor with estimates of total opioid exposure.
  
  
  CONCLUSIONS
  These data support the hypothesis that different aspects of neuropsychological measures of impulsivity appear to be associated with exposure to different opioids. This could reflect either a neurobehavioural consequence of opioid exposure, or may represent an underlying trait vulnerability to opioid dependence.
authors.affiliation: Division of Neuroscience,Medical Research Institute, Ninewells Hospital and Medical School, Dundee University,Dundee,UK.
authors.forename: A
authors.initials: A
authors.lastname: Baldacchino
authors.affiliation: Division of Neuroscience,Medical Research Institute, Ninewells Hospital and Medical School, Dundee University,Dundee,UK.
authors.forename: D J K
authors.initials: DJ
authors.lastname: Balfour
authors.affiliation: Division of Neuroscience,Medical Research Institute, Ninewells Hospital and Medical School, Dundee University,Dundee,UK.
authors.forename: K
authors.initials: K
authors.lastname: Matthews
mesh_terms: D000293:Adolescent; D000328:Adult; D000700:Analgesics / Q000009:adverse effects*; D056344:Executive Function / Q000187:drug effects*; D003932:Heroin / Q000009:adverse effects*; D006556:Heroin Dependence / Q000188:drug therapy; D006801:Humans; D007175:Impulsive Behavior / Q000187:drug effects*; D008297:Male; D008691:Methadone / Q000009:adverse effects*; D058850:Opiate Substitution Treatment; D055815:Young Adult
chemical_list: D000700:Analgesics; D003932:Heroin; D008691:Methadone
keywords: opioid abuse