Phencyclidine

Selected from ongoing neuroimaging studies, thirty-four (29 male, 5 female) well-characterized, chronic, heavy, MJ smokers (22.8 ± 6.57 years) and twenty-eight (19 male, 9 female) non-MJ smoking healthy control participants (24.3 ± 6.64 years) were included in this investigation (see Table 1). Subjects were recruited from the greater Boston area, with participants from both downtown and suburban locations included. Recruitment sites included local colleges and universities, sports clubs and athletic centers, supermarkets, community centers and other public locations. All subjects received the Structured Clinical Interview for DSM-IV, Patient Edition (SCID-P) to ensure that no Axis I pathology was present and that they did not meet criteria for current or previous drug or alcohol abuse or dependence (excluding MJ abuse for the smokers), binge drinking, or routinely had more than 15 drinks per week. Given that diagnostic criteria for both alcohol abuse and dependence are exclusive of the total number of drinks per week, and our desire to enroll subjects without excessive alcohol use, we used criteria that is consistent with several of our previous investigations (Gruber et al., 2009 (link); Gruber, Silveri, Dahlgren & Yurgelun-Todd, 2011 (link); Pope, Gruber, Hudson, Huestis, & Yurgelun-Todd, 2001 (link)). In addition, subjects were excluded if they reported more than 15 lifetime uses of any category of illicit drugs or had a positive urine screen for any illicit drug (excluding MJ for the smokers), were non-native English speakers, if they had ever experienced a head injury with loss of consciousness or associated symptoms or sequelae or reported a neurological disorder, or if they had ever used psychotropic medications.
In order to qualify for study entry, MJ smokers had to have smoked MJ a minimum of 2500 times in their lives, used MJ at least five of the last seven days, test positive for urinary cannabinoids, and meet DSM-IV criteria for MJ abuse or dependence. MJ smokers were required to abstain from smoking for at least 12 hours before cognitive testing to ensure that they were not acutely intoxicated at the time of assessment and were told that they would have to give a urine sample upon arrival at the laboratory. To ensure compliance of the 12-hour abstinence, subjects were led to believe that this sample would allow us to detect use of MJ within this time frame, a method we have used previously with success (Gruber et al. 2011 (link)). Urine samples were tested for MJ, amphetamines, opioids, phencyclidine, barbiturates, benzodiazepines, and cocaine (Triage® Drugs of Abuse Panel: Immediate Response Diagnostics, San Diego, CA). This procedure was required for three reasons: (1) to exclude subjects who tested positive for other substances of abuse, (2) to determine whether subjects had used MJ recently enough to have a positive urine screen, and (3) to encourage subjects, as requested, to abstain from MJ from the previous evening until arriving at the laboratory to ensure subjects were not acutely intoxicated at the time of the visit. Subjects were repeatedly reminded that they would be tested for MJ use upon their arrival at the lab. A portion of the sample was sent to an outside laboratory for quantification of urinary cannabinoid concentration via gas chromatography–mass spectrometry (GC–MS). Prior to participation, study procedures were explained, and all subjects were required to read and sign an informed consent form approved by the McLean Hospital Institutional Review Board, which described in detail the procedures of the study and explained that participation in the study was voluntary.

Healthy cannabis users, ages 18–45, were invited to reside on the secure clinical research unit of the National Institute on Drug Abuse (NIDA) Intramural Research Program, National Institutes of Health during 24 h monitored cannabis abstinence. Participants self-reported cannabis dependence or abuse, and had a positive urine cannabinoid test (50 ng/mL) that supported a history of cannabis exposure. The NIDA Institutional Review Board approved the study. All participants provided written informed consent and were financially compensated for time and inconvenience. Before inclusion, each participant underwent thorough medical (physical exam, ECG, blood, and urine chemistries) and psychological evaluations, including past and recent drug use history. All subjects in this study were required to have normal serum creatinine (0.6–1.2 mg/dL), and have no history or symptoms of renal disease in order to participate. Thus, any changes that occurred in urine creatinine were the result of changes in hydration rather than altered kidney function and/or diet. Twenty-four hour medical surveillance prevented access to unauthorized licit or illicit drugs. In addition, random urine drug tests for amphetamines, cannabinoids, cocaine, opiates, and phencyclidine were performed. All individual urine voids were collected ad libitum for up to 30 days.