LAUSR

Purpose Little is known about the associations between mild intellectual disability (MID), borderline intellectual functioning (BIF) and aggressive behaviour in general mental health care. The study aims to establish the association between aggressive behaviour and MID/BIF, analysing patient characteristics and diagnoses. Method 1174 out of 1565 consecutive in-and outpatients were screened for MID/BIF with the Screener for Intelligence and Learning Disabilities (SCIL) in general mental health care in The Netherlands. During treatment, aggressive behaviour was assessed with the Staff Observation Aggression Scale-Revised (SOAS-R). We calculated odds ratios and performed a logistic and poisson regression to calculate the associations of MID/ BIF, patient characteristics and diagnoses with the probability of aggression. Results Forty-one percent of participating patients were screened positive for MID/BIF. Patients with assumed MID/BIF showed significantly more aggression at the patient and sample level (odds ratio (OR) of 2.50 for aggression and 2.52 for engaging in outwardly directed physical aggression). The proportion of patients engaging in 2–5 repeated aggression incidents was higher in assumed MID (OR = 3.01, 95% CI 1.82–4.95) and MID/BIF (OR = 4.20, 95% CI 2.45–7.22). Logistic regression showed that patients who screened positive for BIF (OR 2,0 95% CL 1.26–3.17), MID (OR 2.89, 95% CI 1.87–4.46), had a bipolar disorder (OR 3.07, 95% CI 1.79–5.28), schizophrenia (OR 2.75, 95% CI 1.80–4.19), and younger age (OR 1.69, 95% CI 1.15–2.50), were more likely to have engaged in any aggression. Poisson regression underlined these findings, showing a SCIL of 15 and below (β = 0.61, p<0.001) was related to more incidents. Conclusions We found an increased risk for aggression and physical aggression in patients with assumed MID/BIF. We recommend screening for intellectual functioning at the start of treatment and using measures to prevent and manage aggressive behaviour that fits patients with MID/BIF.