title: The respiratory effects of cannabis dependence in young adults.
abstract: OBJECTIVE
  To evaluate the relationship between cannabis dependence and respiratory symptoms and lung function in young adults, while controlling for the effects of tobacco smoking.
  
  
  METHODS
  Nine hundred and forty-three young adults from a birth cohort of 1037 subjects born in Dunedin, New Zealand in 1972/1973 were studied at age 21.
  
  
  METHODS
  Standardized respiratory symptom questionnaires were administered. Spirometry and methacholine challenge tests were undertaken. Cannabis dependence was determined using DSM-III-R criteria. Descriptive analyses and comparisons between cannabis-dependent, tobacco-smoking and non-smoking groups were undertaken. Adjusted odds ratios for respiratory symptoms, lung function and airway hyper-responsiveness (PC20) were measured.
  
  
  RESULTS
  Ninety-one subjects (9.7%) were cannabis-dependent and 264 (28.1%) were current tobacco smokers. After controlling for tobacco use, respiratory symptoms associated with cannabis dependence included: wheezing apart from colds, exercise-induced shortness of breath, nocturnal wakening with chest tightness and early morning sputum production. These were increased by 61%, 65%, 72% (all p < 0.05) and 144% (p < 0.01) respectively, compared to non-tobacco smokers. The frequency of respiratory symptoms in cannabis-dependent subjects was similar to tobacco smokers of 1-10 cigarettes/day. The proportion of cannabis-dependent study members with an FEV1/FVC ratio of < 80% was 36% compared to 20% for non-smokers (p = 0.04). These outcomes occurred independently of co-existing bronchial asthma.
  
  
  CONCLUSIONS
  Significant respiratory symptoms and changes in spirometry occur in cannabis-dependent individuals at age 21 years, even although the cannabis smoking history is of relatively short duration.
authors.affiliation: Department of Medicine, Dunedin School of Medicine, University of Otago Medical School, Dunedin, New Zealand. robin.taylor@stonebow.otago.ac.nz
authors.forename: D R
authors.initials: DR
authors.lastname: Taylor
authors.forename: R
authors.initials: R
authors.lastname: Poulton
authors.forename: T E
authors.initials: TE
authors.lastname: Moffitt
authors.forename: P
authors.initials: P
authors.lastname: Ramankutty
authors.forename: M R
authors.initials: MR
authors.lastname: Sears
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D005260:Female; D005541:Forced Expiratory Volume / Q000187:drug effects; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000150:complications*; D012120:Respiration Disorders / Q000139:chemically induced*; D011795:Surveys and Questionnaires; D014797:Vital Capacity