Testing the Validity of the Anticipated DSM-5 Inhalant Use Disorder Diagnosis: An Item Response Theory Analysis

Inhalants, usually taking the form of legal, inexpensive household chemicals, are a prevalent substance of misuse in preteens and teenagers. Use of inhalants is particularly alarming because rates are highest among middle schoolers; Monitoring the Future (MTF) estimates the prevalence of lifetime use among 8^th graders to be just over 13%. Assessing problematic inhalant use relies on diagnostic criteria for abuse/dependence from the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Revised (DSM-IV-TR). Several changes to these criteria are proposed for the DSM, Fifth Edition (DSM-5), and it is also proposed that clinically problematic inhalant use be termed inhalant use disorder.

The present study (1) compared diagnostic agreement between two measures of inhalant use abuse/dependence, the Substance Abuse Module (SAM) and Schedules for Clinical Assessment in Neuropsychiatry (SCAN), and (2) evaluated differences in DSM-IV-TR inhalant abuse/dependence syndromes versus the proposed DSM-5 inhalant use disorder diagnosis. In particular, the unidimensionality of an inhalant use disorder construct, as well as the performance of individual items assessing the disorder, was examined. Special attention was paid to the criterion concerning legal problems associated with use, because the anticipated DSM-5 has proposed dropping the criterion, as well as a proposed new criterion of craving that has not previously been part of an abuse/dependence diagnosis.

A community sample of 162 adolescents and young adults (66.7% male; 83.3% Caucasian; mean age = 20.3 years) from St. Louis, MO was examined. Participants completed a variety of measures including the SAM and SCAN. Concordance between abuse/dependence criteria and diagnosis from the two measures was examined; confirmatory factor analysis was used to examine the unidimensionality of inhalant use disorders. Item response theory (IRT) analyses examined performance of individual items in their utility for DSM-IV-TR diagnoses compared to DSM-5 diagnosis.

Results indicated that diagnostic agreement between SAM and SCAN instruments was weak based on weighted kappa, and abuse/dependence criteria appear to assess a single, unidimensional construct. More specifically, IRT analyses suggested that abuse/dependence criteria lie on a single continuum, removal of the ‘legal problems’ criterion would not alter performance of other criteria, and the proposed ‘craving’ criterion was associated with severe inhalant use disorders. Overall, findings suggest that inhalant use is better conceptualized on one continuum (as proposed for DSM-5), than as separate abuse/dependence diagnoses (as in DSM-IV-TR). Implications for assessment of inhalant use and disorder in prevention research will be discussed.