Comparative trial of the WHO ASSIST-linked brief intervention and simple advice for substance abuse in primary care

•We screened primary care patients with the ASSIST.•We compared the effect of the ASSIST-linked brief intervention and simple advice.•Both brief intervention and simple advice decreased drug use for six months.•Our study supports the benefit of early intervention of drug misuse in primary care.

To help decrease the burden of substance-related problems, the World Health Organization developed the Alcohol, Smoking, Substance Involvement Screening Test (ASSIST) – a sensitive screening questionnaire to help identify misuse of alcohol and other substances – linked to Brief Intervention (BI). This paper compares the effectiveness of the ASSIST followed either by its linked BI or by simple advice (SA). The trial was conducted in southern Thailand. The ASSIST was used to screen patients attending primary care units and categorise them into ‘low-risk’, ‘moderate-risk’ and ‘high-risk’ groups. Patients at ‘moderate-risk’ were randomised to receive ASSIST-linked BI (n = 120) or SA (n = 116). The outcome measures were changes in the ASSIST-Specific Substance Involvement Scores (ASSIST-SSIS), ASSIST-Total Substance Involvement Scores (ASSIST-TSIS) and proportions of patients whose scores at three and six months had decreased from the ‘moderate-risk’ to ‘low-risk’ category. 147 patients (72 BI; 75 SA) completed the six-month trial. There were significant reductions in both ASSIST-SSIS and ASSIST-TSIS, with no significant difference between groups. The percentages of patients converted to the ‘low-risk’ category were 36.7% and 38.8% at month 3, and 53.3% and 53.4% at month 6, for the BI and SA groups, respectively. In conclusion, in primary care administering the ASSIST and telling patients their score, followed either by formal brief intervention or simple advice, are equally effective in decreasing substance use for up to six months.