title: Contingent Vs. Non-Contingent Rewards: Time-Based Intervention Response Patterns Among Stimulant-Using Men Who Have Sex With Men.
abstract: Stimulant use rates are higher among men who have sex with men (MSM) than the general population. Contingency management (CM) may be an effective intervention for reducing stimulant use in this population. To specify both the mechanism and temporal effects of contingent reward on behavior change, logistic growth trajectory modeling (LGTM) was used to contrast a non-contingent matched rewards condition (i.e., non-contingent yoked controls; NCYC) to a voucher-based CM intervention (maximum=$430) to reduce stimulant use among MSM. Stimulant-using MSM were randomized to either a CM intervention (n=70) or a NCYC condition (n=70). Results from a LGTM (analytical sample n=119; nCM=61; nNCYC=58) indicated four distinct intervention response patterns: responders (i.e., predicted >90% stimulant metabolite-free urinalyses; 64.7% of sample); worsening intervention response (14.3%); non-responders (12.6%); and, single-positive (8.4%); all estimated trajectory coefficients were significant at p<0.03 (2-tailed). Participants receiving CM were significantly overrepresented in the responder (64%) and single-positive (80%) categories (χ2(3)=29.04; p<0.001); all non-responders and 76.5% of the worsening intervention response category were in the NCYC condition. Results demonstrate the utility of trajectory modeling and further support the contingent application of reward as the operative mechanism associated with patterns of stimulant abstinence with CM applied to a sample of stimulant-using MSM outside the context of formal drug treatment.
authors.affiliation: Department of Family Medicine, University of California, 10880 Wilshire Blvd Suite 1800, Los Angeles, CA 90024.
authors.forename: Steven
authors.initials: S
authors.lastname: Shoptaw
authors.affiliation: Center for Clinical AIDS Research & Education, University of California, 11075 Santa Monica Blvd, Suite 100, Los Angeles, CA 90025.
authors.forename: Raphael J
authors.initials: RJ
authors.lastname: Landovitz
authors.affiliation: Friends Research Institute, Inc., 1419 La Brea Ave, Los Angeles, CA 90028; Integrated Substance Abuse Programs, Semel Institute for Neuroscience and Human Behavior, University of California, 11075 Santa Monica Blvd Suite 200, Los Angeles, CA 90025. Electronic address: reback@friendsresearch.org.
authors.forename: Cathy J
authors.initials: CJ
authors.lastname: Reback
mesh_terms: D000328:Adult; D019969:Amphetamine-Related Disorders / Q000628:therapy* / Q000652:urine; D001521:Behavior Therapy / Q000379:methods*; D001727:Bisexuality; D018451:Homosexuality, Male; D006801:Humans; D008297:Male; D008875:Middle Aged; D010043:Outcome and Process Assessment, Health Care; D012201:Reward; D013997:Time Factors
keywords: Contingency management; HIV; Men who have sex with men (MSM); Methamphetamine; Stimulants