Introduction: adverse childhood experiences are related to mental health problems and substance use in adulthood and are defined as a series of events and experiences perceived as harmful by children and adolescents. Objective: to establish the relationship between Adverse Childhood Experiences, Family Functionality and Severity of Psychoactive Substance Dependence in adults. Method: quantitative, correlational-exploratory, non-experimental and cross-sectional study, in a population of 152 people in treatment for substance use during the year 2023, between 18 and 65 years of age, with a focus on 5 public treatment centers in Chile, with a purposive sample of 64 cases. An instrument composed of 3 scales was applied, and descriptive analysis, correlations and linear regression were carried out. Results: there is a high correlation in the 5 subscales of the CTQ-SF of Early Adverse Experiences. The lower the Family Functionality, the higher the levels of Early Adverse Experiences. The detached/separated type of families predominate, but Family Functionality does not correlate significantly with Severity of Psychoactive Substance Dependence. Discussion: psychoactive substance severity does correlate significantly positively with living Early Adverse Experiences. Likewise, the study positively signifies the joint relationship of predictor variables. Conclusions: early adverse experience is related to problematic substance use in adulthood, the traumatic event arises within the family, systemically affecting mental health in adulthood, independent of its structure and compositio
