Heterogeneity of stimulant dependence: A National Drug Abuse Treatment Clinical Trials Network study.

In this study, the presence of DSM-IV subtyping for dependence on cocaine and amphetamines (with vs. without physical dependence) was investigated among outpatient stimulant users enrolled in a multisite study of the Clinical Trials Network (CTN-0006). Three mutually exclusive groups were identified: primary cocaine users (n=287), primary amphetamine users (n=99), and dual users (cocaine and amphetamines; n=29). Distinct subtypes were examined with latent class and logistic regression procedures. Cocaine users were distinct from amphetamine users in age and race/ethnicity. There were four distinct classes of primary cocaine users: non-dependence (15%), compulsive use (14%), tolerance and compulsive use (15%), and physiological dependence (tolerance, withdrawal, and compulsive use; 56%). Three distinct classes of primary amphetamine users were identified: nondependence (11%), intermediate physiological dependence (31%), and physiological dependence (58%). Regardless of stimulants used, most female users were in the most severe or the physiological dependence group. These results lend support for subtyping dependence in the emerging DSM-IV, however, DSM-IV employs a broad definition of the presence of either tolerance or withdrawal to define a physiological component.

Results from this investigation and others suggest that tolerance alone is not a good indicator for determining the importance of designating a physiologic component in DSM-IV. For the emerging DSM-V, a more narrow definition requiring both tolerance and withdrawal should be considered and investigated further to validate its existence for different population subgroups.

Supported by the Duke Clinical Research Institute (CTN DSC 1).

Related protocols: CTN-0006