Evaluating the drug use "gateway" theory using cross-national data: consistency and associations of the order of initiation of drug use among participants in the WHO World Mental Health Surveys.
BACKGROUND
It is unclear whether the normative sequence of drug use initiation, beginning with tobacco and alcohol, progressing to cannabis and then other illicit drugs, is due to causal effects of specific earlier drug use promoting progression, or to influences of other variables such as drug availability and attitudes. One way to investigate this is to see whether risk of later drug use in the sequence, conditional on use of drugs earlier in the sequence, changes according to time-space variation in use prevalence. We compared patterns and order of initiation of alcohol, tobacco, cannabis, and other illicit drug use across 17 countries with a wide range of drug use prevalence.


METHODS
Analyses used data from World Health Organization (WHO) World Mental Health (WMH) Surveys, a series of parallel community epidemiological surveys using the same instruments and field procedures carried out in 17 countries throughout the world.


RESULTS
Initiation of "gateway" substances (i.e. alcohol, tobacco and cannabis) was differentially associated with subsequent onset of other illicit drug use based on background prevalence of gateway substance use. Cross-country differences in substance use prevalence also corresponded to differences in the likelihood of individuals reporting a non-normative sequence of substance initiation.


CONCLUSIONS
These results suggest the "gateway" pattern at least partially reflects unmeasured common causes rather than causal effects of specific drugs on subsequent use of others. This implies that successful efforts to prevent use of specific "gateway" drugs may not in themselves lead to major reductions in the use of later drugs.
Degenhardt
Louisa
L
National Drug and Alcohol Research Centre, University of New South Wales, Sydney, NSW 2052, Australia. l.degenhardt@unsw.edu.au
Dierker
Lisa
L
Chiu
Wai Tat
WT
Medina-Mora
Maria Elena
ME
Neumark
Yehuda
Y
Sampson
Nancy
N
Alonso
Jordi
J
Angermeyer
Matthias
M
Anthony
James C
JC
Bruffaerts
Ronny
R
de Girolamo
Giovanni
G
de Graaf
Ron
R
Gureje
Oye
O
Karam
Aimee N
AN
Kostyuchenko
Stanislav
S
Lee
Sing
S
Lépine
Jean-Pierre
JP
Levinson
Daphna
D
Nakamura
Yosikazu
Y
Posada-Villa
Jose
J
Stein
Dan
D
Wells
J Elisabeth
JE
Kessler
Ronald C
RC
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000437:Alcoholism / Q000453:epidemiology; D015331:Cohort Studies; D016208:Databases, Factual; D017831:Diagnosis, Dual (Psychiatry); D018450:Disease Progression; D005260:Female; D006801:Humans; D007406:Interview, Psychological; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology; D001523:Mental Disorders / Q000453:epidemiology; D008875:Middle Aged; D012907:Smoking / Q000453:epidemiology; D019966:Substance-Related Disorders / Q000453:epidemiology* / Q000523:psychology; D014944:World Health Organization; D055815:Young Adult