Subtypes of illicit drug users: a latent class analysis of data from an Australian twin sample.
This article applies methods of latent class analysis (LCA) to data on lifetime illicit drug use in order to determine whether qualitatively distinct classes of illicit drug users can be identified. Self-report data on lifetime illicit drug use (cannabis, stimulants, hallucinogens, sedatives, inhalants, cocaine, opioids and solvents) collected from a sample of 6265 Australian twins (average age 30 years) were analyzed using LCA. Rates of childhood sexual and physical abuse, lifetime alcohol and tobacco dependence, symptoms of illicit drug abuse/dependence and psychiatric comorbidity were compared across classes using multinomial logistic regression. LCA identified a 5-class model: Class 1 (68.5%) had low risks of the use of all drugs except cannabis; Class 2 (17.8%) had moderate risks of the use of all drugs; Class 3 (6.6%) had high rates of cocaine, other stimulant and hallucinogen use but lower risks for the use of sedatives or opioids. Conversely, Class 4 (3.0%) had relatively low risks of cocaine, other stimulant or hallucinogen use but high rates of sedative and opioid use. Finally, Class 5 (4.2%) had uniformly high probabilities for the use of all drugs. Rates of psychiatric comorbidity were highest in the polydrug class although the sedative/opioid class had elevated rates of depression/suicidal behaviors and exposure to childhood abuse. Aggregation of population-level data may obscure important subgroup differences in patterns of illicit drug use and psychiatric comorbidity. Further exploration of a 'self-medicating' subgroup is needed.
Lynskey
Michael T
MT
Department of Psychiatry, Washington University School of Medicine, St Louis, Missouri 63110, United States of America. mlynskey@wustl.edu
Agrawal
Arpana
A
Bucholz
Kathleen K
KK
Nelson
Elliot C
EC
Madden
Pamela A F
PA
Todorov
Alexandre A
AA
Grant
Julia D
JD
Martin
Nicholas G
NG
Heath
Andrew C
AC
D001315:Australia; D002648:Child; D002650:Child Abuse, Sexual / Q000401:mortality / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D012307:Risk Factors; D019966:Substance-Related Disorders / Q000145:classification / Q000401:mortality / Q000523:psychology; D018433:Twin Studies as Topic; D014427:Twins