Substance use disorders in patients with intellectual disability admitted to psychiatric hospitalisation

Few studies have looked at the prevalence of substance use disorders (SUD) in people with intellectual disability (ID). The results range between 1% and 6.4% and go up to 20% in people with ID and psychiatric disorders, probably underestimating real prevalence due to several limitations in these studies. ID confers risk for the development of SUD, which in turn will involve negative psychosocial and clinical consequences. We aimed to study the prevalence of SUD in a sample of patients with ID admitted to a brief hospitalisation psychiatric unit, describing them by type and severity and analysing their relationship with clinical, prognostic and access to treatment variables.

We undertook a descriptive, cross-sectional and retrospective study by means of a review of clinical histories of all patients with a diagnosis of ID, admitted in a period of 10 years.

Among the final sample of patients included, 52.3% had a mild ID, 40.9% an unspecified ID, 3.4% a moderate ID and another 3.4% a severe ID. More than one third of the sample met criteria for a SUD. The main SUD was cannabis use disorder (25%), followed by alcohol use disorder (22.7%) and cocaine use disorder (13.6%). The use of more than one substance was the most frequent pattern. Cannabis use disorder and cocaine use disorder were overrepresented in the group with mild ID. A greater number of psychiatric admissions was observed for the group with SUD. Specialised mental health services for ID and specialised addiction network facilities were much less involved in the care of these patients that could be expected according to good clinical practice recommendations.

Substance use disorder in patients with ID and mental health disorders admitted to psychiatric hospitalisation are prevalent, which makes this issue an area of interest for future improvements in case identification, proper referring to specialised treatment resources and an increasing research focusing on specific therapeutic approaches.