title: Cognitive and subjective effects of mephedrone and factors influencing use of a 'new legal high'.
abstract: OBJECTIVE
  Use of the stimulant drug mephedrone increased dramatically in 2009, and it is still available in the United Kingdom after being controlled in April 2010. This study aimed to assess mephedrone's acute cognitive and subjective effects.
  
  
  METHODS
  A mixed within- and between-subjects design compared 20 mephedrone users, first while intoxicated (T1) and secondly drug free (T2); and 20 controls twice when drug free (T1 and T2).
  
  
  METHODS
  Participants' own homes.
  
  
  METHODS
  Healthy adults recruited from the community.
  
  
  METHODS
  Subjective effects, episodic and working memory, phonological and semantic fluency, psychomotor speed and executive control at were assessed at T1 and T2. Trait schizotypy, depression, changes in mephedrone use since the ban and attitudes influencing use of a hypothetical new legal high were indexed at T2 only.
  
  
  RESULTS
  Compared with controls, mephedrone users had generally impaired prose recall (P = 0.037) and higher scores in schizotypy (P < 0.001) and depression (P = 0.01). Mephedrone acutely primed a marked 'wanting' for the drug (P < 0.001), induced stimulant-like effects, impaired working memory (P < 0.001) and enhanced psychomotor speed (P = 0.024). Impulsivity in mephedrone users correlated with the number of hours in an average (nearly 8 hour) mephedrone session (r = 0.6). Users would be drawn to use a new legal high if it were pure, had no long/short term harms, and was positively rated by friends or on the internet.
  
  
  CONCLUSIONS
  Mephedrone impairs working memory acutely, induces stimulant-like effects in users and is associated with binge use. Factors that influence users' attitudes to new drugs might help to predict future trends in use of the many new psychoactive substances emerging on the internet.
authors.affiliation: Clinical Psychopharmacology Unit, Clinical Health Psychology, University College London, UK. tom.freeman@ucl.ac.uk
authors.forename: Tom P
authors.initials: TP
authors.lastname: Freeman
authors.forename: Celia J A
authors.initials: CJ
authors.lastname: Morgan
authors.forename: James
authors.initials: J
authors.lastname: Vaughn-Jones
authors.forename: Nahida
authors.initials: N
authors.lastname: Hussain
authors.forename: Kash
authors.initials: K
authors.lastname: Karimi
authors.forename: H Valerie
authors.initials: HV
authors.lastname: Curran
mesh_terms: D016022:Case-Control Studies; D000697:Central Nervous System Stimulants / Q000009:adverse effects*; D056344:Executive Function / Q000187:drug effects*; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced*; D008694:Methamphetamine / Q000009:adverse effects / Q000031:analogs & derivatives*; D011596:Psychomotor Disorders / Q000139:chemically induced*; D013064:Speech Disorders / Q000139:chemically induced; D019966:Substance-Related Disorders / Q000150:complications*; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D008694:Methamphetamine; C548233:mephedrone