Estimated rapid transition from first stimulant use until onset of stimulant dependence: Larger for methamphetamine users?

Aims: We expected newly incident methamphetamine users (NIMU) to show stimulant dependence transition probabilities (SDTP) resembling those seen for newly incident cocaine users (NICU; i.e., with 5–6% becoming dependent within 12 months of 1st use), and with lower SDTP estimates seen for newly incident extra-medical users of stimulants (NIEMSU) when METH has not been used. Methods: Data are from 2002–2011 US National Surveys on Drug Use and Health (RDAS), yielding nationally representative samples of more than 4000 NIEMSU and NIMU, all assessed via confidential computer-assisted self-interviews. Estimates fromfive independent year-pair replicationswith analysis-weights and Taylor series variance estimation are summarized usingmeta-analysis. Results: For NIEMSU, the meta-analytic SDTP estimate is 4.1% (95% CI =3.1, 5.0). For NIMU, the corresponding STDP estimate is 3.3% (95% CI =1.5, 5.0). Conclusions: Our presentation will extend this line of stimulant dependence research with subgroup analyses intended to help us understand lower STDP estimates for NIMU as compared to NICU and the NIEMSU with no METH use, which contradicted our expectations. Strata of interest involve METH injection versus other routes of administration, onset-age, which stimulant product is used byNIEMSU, andwhether there is concurrent or past cocaine use. Financial support: NIDA OSR (T32DA021129); JCA (K05DA015799).