UNDERREPORTING OF COCAINE USE AT POSTTREATMENT FOLLOW-UP AND THE MEASUREMENT OF TREATMENT EFFECTIVENESS

Substance abusers, especially cocaine abusers, may underreport their s ubstance use in outcome interviews. Follow-up interviews were conducte d and urine specimens were obtained on 633 persons 9 months after admi ssion to a 3-month cocaine treatment program. Although 422 (67%) repor ted no use of cocaine in the past 30 days, 134 of these (32%) had coca ine-positive urines. This group did not differ on most characteristics at intake or follow-up from the 288 with cocaine-negative wines. The amount of treatment received did affect willingness to admit drug use. Of 132 treatment completers who reported no cocaine use at follow-up, 21 (16%) had positive urines. Of 91 early dropouts who also reported no cocaine use: 36 (40%) had positive urines. This differential rate o f underreporting had the effect of seriously underrepresenting the eff ectiveness of treatment completion as compared with little or no treat ment.