"Youthful epidemic" or diagnostic bias? Differential item functioning of DSM-IV cannabis use criteria in an Australian general population survey.
BACKGROUND
Prevalence rates of cannabis abuse and dependence are higher for younger adults when compared with older adults. It is necessary to examine the performance of criteria across age groups to establish whether these differences in prevalence rates are a result of diagnostic bias. The current study aims to investigate whether there is any age-related differential item functioning in the DSM-IV diagnostic criteria for cannabis use disorders using an item response theory approach.


METHODS
The sample consisted of 10,641 participants in a population-based survey of Australian adults aged 18 years and older. DSM-IV cannabis use disorders were assessed in all respondents who had used cannabis more than five times in the previous twelve months (n=722). Age-based differential item functioning was assessed in each of the DSM-IV criteria for cannabis use disorders.


RESULTS
Age-based differential item functioning was only detected in the Hazard criterion of the DSM-IV cannabis use disorders. The Hazard criterion was found to be more discriminating for those aged 18-24 when compared with those aged 25 and over.


CONCLUSIONS
The DSM-IV criteria for cannabis use disorders appear to function similarly across age groups. Differential item functioning was only detected in the alpha parameter for the Hazard criterion. These results are discussed with regard to implications for future editions of the DSM system.
Mewton
Louise
L
National Drug and Alcohol Research Centre, University of New South Wales, NSW 2052, Australia. louisem@unsw.edu.au
Teesson
Maree
M
Slade
Tim
T
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001315:Australia / Q000453:epidemiology; D015982:Bias; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis / Q000453:epidemiology*; D015995:Prevalence; D055815:Young Adult