The prevalence of self-harm and mental disorders among individuals with intellectual disabilities

Mental health disorders are prevalent among individuals with intellectual disabilities (ID). However, there is a lack of research on the impact of concomitant autism spectrum disorders (ASD) or attention deficit hyperactivity disorder (ADHD) on the mental health within this population. We aimed to investigate the prevalence of mental health disorders and registered healthcare visits due to self-harm among individuals with ID.

We used administrative data for all healthcare with at least one recorded diagnosis of mental health disorder or self-harm during 2007-2017 among people with a diagnosis of Down syndrome (DS; n = 1298) and with ID without DS (IDnonDS; n = 10,671) using the rest of the population in Stockholm Region (n = 2,048,488) for comparison.

The highest odds ratios for a mental health disorder were present in females with IDnonDS (9.01) followed by males with IDnonDS (8.50), compared to the general population. The ORs for self-harm among individuals with IDnonDS were high (8.00 for females and 6.60 for males). There were no registered cases of self-harm among individuals with DS. The prevalence of an anxiety or affective disorder was higher among individuals with ID including DS with concomitant ASD or ADHD. Neighbourhood socio-economic status was associated with a lower occurrence of mental health disorders and self-harm in wealthier areas for all outcomes and for all groups.

Self-harm and psychiatric comorbidities were common among individuals with ID without DS with an attenuated difference among those with concomitant ASD or ADHD, which calls for attention.