The association between speed of transition from initiation to subsequent use of cannabis and later problematic cannabis use, abuse and dependence.
OBJECTIVE
To test whether speed of transition from initiation use to subsequent use of cannabis is associated with likelihood of later cannabis dependence and other outcomes, and whether transition speed is attributable to genetic or environmental factors.


METHODS
Cross-sectional interview study.


METHODS
Australia.


METHODS
A total of 2239 twins and siblings who reported using cannabis at least twice [mean age at time of survey = 32.0, 95% confidence interval (CI) = 31.9 - 32.1, range = 22-45].


METHODS
Time between initiation and subsequent cannabis use (within 1 week; within 3 months; between 3 and 12 months; more than 1 year later), later use of cannabis and symptoms of DSM-IV cannabis abuse/dependence. Multinomial regression analyses (comparison group: more than 1 year later) adjusted the association between speed of transition and the outcomes of cannabis daily use, abuse/dependence and treatment-seeking after controlling for socio-demographic, childhood, mental health, peer and licit drug factors. Twin modelling estimated the proportion of variance in transition speed attributable to genetic (A), common environment (C) and unique environmental (E) factors.


RESULTS
Subsequent use of cannabis within 1 week of initiation was associated with daily use [odds ratio (OR) = 2.64, 95% CI = 1.75-3.99], abuse and/or dependence (OR = 3.25, 95% CI = 2.31-4.56) and treatment-seeking for cannabis problems (OR = 1.89, 95% CI = 1.03-3.46). Subsequent use within 3 months was associated with abuse and/or dependence (OR = 1.61, 95% CI = 1.18-2.19). The majority of the variation of the speed of transition was accounted for by unique environment factors (0.75).


CONCLUSIONS
Rapid transition from initiation to subsequent use of cannabis is associated with increased likelihood of subsequent daily cannabis use and abuse/dependence.
Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
Lindsey A
LA
Hines
Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
Katherine I
http://orcid.org/0000-0002-2725-5535
KI
Morley
Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
John
J
Strang
Department of Psychiatry, Washington University School of Medicine, St Louis, MO, USA.
Arpana
A
Agrawal
Department of Psychiatry, Washington University School of Medicine, St Louis, MO, USA.
Elliot C
EC
Nelson
School of Social Sciences, University of the Sunshine Coast, Queensland, Australia.
Dixie
D
Statham
QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
Nicholas G
NG
Martin
Addictions Department, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
Michael T
MT
Lynskey
D000328:Adult; D017668:Age of Onset; D000428:Alcohol Drinking / Q000453:epidemiology; D001315:Australia / Q000453:epidemiology; D002648:Child; D002650:Child Abuse, Sexual / Q000706:statistics & numerical data; D016241:Child of Impaired Parents / Q000706:statistics & numerical data; D019955:Conduct Disorder / Q000453:epidemiology; D003866:Depressive Disorder / Q000453:epidemiology; D004522:Educational Status; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007398:Interpersonal Relations; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology* / Q000209:etiology; D008385:Marijuana Smoking / Q000453:epidemiology*; D008875:Middle Aged; D012907:Smoking / Q000453:epidemiology; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D055815:Young Adult
Cannabis; cannabis abuse; cannabis dependence; initiation; subsequent use; transitions; twin study