OBJECTIVE: To determine severity clusters (groups) of substance use in crack cocaine users by the severity scores of the sixth version of the Addiction Severity Index (ASI-6) and compare the groups detected in relation to risk factors as parental styles, childhood maltreatment, and impulsivity. METHODS: A cross-sectional study was conducted with 531 male adults with Substance Use Disorder, admitted to a hospital treatment unit for addiction in Southern Brazil. In order to detect more homogeneous groups of individuals, the approach used involves the K-means clustering using ASI-6 scores to create clusters or groups of individuals with similar severity in different areas. Parenting styles were assessed using the Measure of Parental Style, childhood trauma was assessed using the Childhood Trauma Questionnaire, and the patients' impulsivity was measured using the Barratt Impulsivity Scale 11. Poisson Regression was used for association analysis. RESULTS: Two distinct clusters (groups) were identified, which differed significantly across all composite scores (p<
0.001). These associations were further confirmed through Poisson Regression analysis. The more severe cluster showed significantly higher scores for maternal abuse (p=0.026), sexual abuse (p=0.003), motor impulsivity (p=0.014) and unplanned above the 75th Percentile (p=0.032) compared to the less severe group. Other parenting styles, types of trauma and impulsivity were not significant different between the groups. CONCLUSIONS: The division into severity clusters contributes to the proposition of more targeted treatments. More research focusing on outpatients would be important to reinforce the impact on preventing early life factors and treating impulsivity.