Consequences of Prolonged Substance Use Disorder in Psychosis, ADHD and Violence: 6 Month Follow-Up Study

Background: Substance Use Disorder (SUD) is frequently associated with psychiatric comorbidity, including psychotic symptoms, impulsivity and neurodevelopmental traits. The influence of age and duration of substance use on these clinical characteristics and on treatment retention remains insufficiently understood. Objectives: To examine the influence between age, duration of substance use, clinical presentation, patterns of violence, and treatment retention in individuals with SUD. Methods: A prospective 6-month cohort study was conducted at the Alcoholism Treatment Unit of the CAUSA Hospital Complex in Salamanca, Spain. A total of 264 patients with SUD were classified into two groups: prolonged substance use (≥55 years of age or ≥25 years of substance use; n = 127) and shorter substance use trajectories (<55 years and <25 years of substance use; n = 137). Participants completed structured clinical interviews and validated measures of quality of life, impulsivity, autistic traits, addiction severity, psychotic symptoms and violence. Non-parametric analyses were applied (α = 0.05; 95% CI). Results: Younger participants showed a significantly higher prevalence of auditory and visual hallucinations and persecutory delusions at baseline. During follow-up, both groups exhibited a reduction in physical aggression while driving and an increase in insults and verbal threats. No significant differences were observed in recent uncontrolled violence. Positive screening results for ADHD, autistic traits and impulsivity were not associated with treatment retention. Lower baseline physical functioning was associated with reduced completion of the 6-month follow-up assessment. Conclusions: Age and duration of substance use were associated with differences in the clinical presentation of SUD. Younger individuals exhibited a greater burden of psychotic symptoms and violence-related behaviours, whereas poorer physical functioning was associated with lower follow-up retention among individuals with prolonged substance use histories. These findings support the importance of age-sensitive assessment and management strategies in patients with SUD.