Measurement of Impulsivity and Its Role in Drug Use Behaviours and Related Health, Harm and Treatment Outcomes Among People Who Use Illicit Drugs-A Scoping Review.

Impulsivity is closely implicated in substance use disorders; however, its definition and assessment among people who use illicit drugs (PWUD) are lacking consistency. This scoping review maps the existing evidence on how impulsivity has been defined, measured, and linked to drug use behaviours and consequences. A systematic search of manuscripts (1990-2025) was conducted across multiple databases, identifying 267 eligible studies. Behavioural tasks (76%) were more commonly used to measure impulsivity compared to self-reported tools (44%). The most frequently used behavioural tasks included the Iowa Gambling Task (26%) (cognitive, decision-making and risk-taking impulsivity) and the Go No-Go Task (23%) (motor impulsivity). Studies relying on self-reported measures primarily used the Barratt Impulsivity Scale (N = 86, 73%). Many studies assessed the association between impulsivity and drug use patterns (39%) and treatment-related variables (40%), with fewer examining risk behaviours (13%) and drug-related consequences (23%). Despite growing research, inconsistencies in impulsivity measurements hinder interpretation and comparability of findings. A universal measurement approach is needed to assess impulsivity in PWUD.