Does the 'gateway' matter? Associations between the order of drug use initiation and the development of drug dependence in the National Comorbidity Study Replication.
BACKGROUND
The 'gateway' pattern of drug initiation describes a normative sequence, beginning with alcohol and tobacco use, followed by cannabis, then other illicit drugs. Previous work has suggested that 'violations' of this sequence may be predictors of later problems but other determinants were not considered. We have examined the role of pre-existing mental disorders and sociodemographics in explaining the predictive effects of violations using data from the US National Comorbidity Survey Replication (NCS-R).


METHODS
The NCS-R is a nationally representative face-to-face household survey of 9282 English-speaking respondents aged 18 years and older that used the World Health Organization (WHO) Composite International Diagnostic Interview (CIDI) to assess DSM-IV mental and substance disorders. Drug initiation was estimated using retrospective age-of-onset reports and 'violations' defined as inconsistent with the normative initiation order. Predictors of violations were examined using multivariable logistic regressions. Discrete-time survival analysis was used to see whether violations predicted progression to dependence.


RESULTS
Gateway violations were largely unrelated to later dependence risk, with the exception of small increases in risk of alcohol and other illicit drug dependence for those who initiated use of other illicit drugs before cannabis. Early-onset internalizing disorders were predictors of gateway violations, and both internalizing and externalizing disorders increased the risks of dependence among users of all drugs.


CONCLUSIONS
Drug use initiation follows a strong normative pattern, deviations from which are not strongly predictive of later problems. By contrast, adolescents who have already developed mental health problems are at risk for deviations from the normative sequence of drug initiation and for the development of dependence.
Degenhardt
L
L
National Drug and Alcohol Research Centre, University of NSW, Sydney, NSW, Australia. l.degenhardt@unsw.edu.au
Chiu
W T
WT
Conway
K
K
Dierker
L
L
Glantz
M
M
Kalaydjian
A
A
Merikangas
K
K
Sampson
N
N
Swendsen
J
J
Kessler
R C
RC
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D017668:Age of Onset; D000437:Alcoholism / Q000453:epidemiology / Q000523:psychology; D015897:Comorbidity; D018450:Disease Progression; D005260:Female; D006306:Health Surveys; D006801:Humans; D007389:Internal-External Control; D007406:Interview, Psychological / Q000379:methods; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000523:psychology; D001523:Mental Disorders / Q000453:epidemiology / Q000523:psychology; D008875:Middle Aged; D016017:Odds Ratio; D011237:Predictive Value of Tests; D012307:Risk Factors; D012959:Socioeconomic Factors; D019966:Substance-Related Disorders / Q000453:epidemiology* / Q000523:psychology; D014029:Tobacco Use Disorder / Q000453:epidemiology / Q000523:psychology; D014481:United States / Q000453:epidemiology; D055815:Young Adult