Abstract
OBJECTIVE: Alcohol use disorder (AUD) clinical trials have traditionally prioritized abstinence, and more recently, heavy drinking cessation as primary treatment endpoints. Reductions in World Health Organization (WHO) risk drinking levels may offer a viable harm reduction-aligned alternative. Despite evidence supporting WHO risk level reductions as meaningful indicators of AUD treatment response, their utility in individuals with co-occurring posttraumatic stress disorder (PTSD) remains unknown. The present study compared 1- and 2-level WHO risk drinking reductions with abstinence and heavy drinking (HD) outcomes, and assessed their sensitivity across PTSD and substance use disorder (SUD) interventions, including behavioral and pharmacological treatments. METHODS: We conducted an integrative data analysis of 10 trials for adults with comorbid PTSD and SUD (PTSD+SUD). The proportion of participants achieving each of the four alcohol outcomes was calculated. Logistic regression models assessed treatment effects relative to treatment as usual (TAU). RESULTS: Across the 10 trials (N = 433; mean [SD] age, 39.7 [11.6] years; 359 [73.0 %] men), the most frequently achieved drinking outcome at end-of-treatment was a 1 + level WHO risk reduction (82.8 %), followed by a 2 + level reduction (72.2 %), HD cessation (65.6 %) and, least frequently, abstinence (53.0 %). Pharmacological interventions significantly outperformed TAU across all drinking outcomes. CONCLUSIONS: Findings provide initial support for WHO risk drinking levels as viable endpoints in PTSD+SUD trials. Given their attainability, WHO risk levels may provide clinically relevant outcome metrics for these interventions. Future research should assess whether such reductions correspond to improvements in alcohol-related harms and broader functional outcomes.