title: Cross-sectional and prospective relation of cannabis potency, dosing and smoking behaviour with cannabis dependence: an ecological study.
abstract: OBJECTIVE
  Increased delta-9-tetrahydrocannabinol (THC) concentrations in cannabis may lead to higher THC exposure, cannabis dependence and treatment need, but users may also adapt the actual intake of THC through reduced inhalation of THC containing smoke (titration). We investigated whether consumers of stronger cannabis use less cannabis per joint or inhale less smoke than those using less potent cannabis and whether these factors predict cannabis dependence severity.
  
  
  METHODS
  Heavy cannabis users (n = 98) brought their own cannabis, rolled a joint and smoked it ad libitum in a naturalistic setting. We analysed the content of the joint, its association with smoking behaviour and the cross-sectional and prospective (1.5-year follow-up) relations between smoking behaviour and cannabis dependence severity (total number of DSM-IV dependence symptoms).
  
  
  RESULTS
  THC concentration in cannabis (range 1.10-24.70%) was correlated positively with cannabis dose per joint (b = 0.008, P = 0.01), but the resulting THC concentration per joint (range 0.24-15.72%) was associated negatively with inhalation volume (b = -0.05, P = 0.03). Smoking behaviour measures (number of puffs, inhaled volume, reduction of puff volume and puff duration while smoking) predicted follow-up dependence severity, independently of baseline dependence severity and monthly THC dose (number of joints × cannabis dose × cannabis THC concentration). Monthly THC dose only predicted follow-up dependence severity when unadjusted for baseline severity.
  
  
  CONCLUSIONS
  Cannabis users titrate their delta-9-tetrahydrocannabinol intake by inhaling lower volumes of smoke when smoking strong joints, but this does not fully compensate for the higher cannabis doses per joint when using strong cannabis. Thus, users of more potent cannabis are generally exposed to more delta-9-tetrahydrocannabinol. Smoking behaviour appears to be a stronger predictor for cannabis dependence severity than monthly delta-9-tetrahydrocannabinol dose.
authors.affiliation: Trimbos Institute, Netherlands Institute of Mental Health and Addiction, Utrecht, the Netherlands.
authors.forename: Peggy
authors.initials: P
authors.lastname: van der Pol
authors.forename: Nienke
authors.initials: N
authors.lastname: Liebregts
authors.forename: Tibor
authors.initials: T
authors.lastname: Brunt
authors.forename: Jan
authors.initials: J
authors.lastname: van Amsterdam
authors.forename: Ron
authors.initials: R
authors.lastname: de Graaf
authors.forename: Dirk J
authors.initials: DJ
authors.lastname: Korf
authors.forename: Wim
authors.initials: W
authors.lastname: van den Brink
authors.forename: Margriet
authors.initials: M
authors.lastname: van Laar
mesh_terms: D000328:Adult; D002188:Cannabis / Q000737:chemistry*; D002849:Chromatography, Gas; D003430:Cross-Sectional Studies; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology*; D008385:Marijuana Smoking / Q000453:epidemiology*; D009426:Netherlands / Q000453:epidemiology; D011446:Prospective Studies; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D013759:Dronabinol
keywords: Dose; THC concentration; exposure; frequent cannabis use; marijuana; smoking topography; titration