Psychiatric disorders in adolescents and adults with autism and intellectual disability: a representative study in one county in Norway.
Over half of autistic teens and adults with ID carry extra psychiatric diagnoses, so yearly mental-health screens are essential.
01Research in Context
What this study did
Researchers counted psychiatric disorders in every adolescent and adult with autism plus intellectual disability living in one Norwegian county. They used the Psychopathology in Autism Checklist (PAC) and strict DSM criteria. The team also checked a comparison group who had ID without autism.
What they found
Over half of the autism-plus-ID group had at least one psychiatric diagnosis. Anxiety showed the biggest gap between the groups. Six out of ten people had two or more disorders at the same time.
How this fits with other research
Halvorsen et al. (2025) later showed the PAC tool itself is reliable, so these numbers hold up. Badia et al. (2013) found high anxiety in autistic youth without ID, while this paper finds the same in the ID group; IQ cut-offs explain the difference. Totsika et al. (2010) saw no extra psychiatric risk from autism once adaptive skills were counted, but their sample was adults over 50 and they adjusted the data; the current study gives raw rates in a mixed-age group.
Why it matters
If you serve teens or adults with both autism and ID, plan to screen for anxiety, depression, OCD and psychosis every year. Use a checklist like the PAC and watch for stacked disorders. Flagging these issues early can cut crisis visits and improve quality of life.
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02At a glance
03Original abstract
UNLABELLED: Few studies assess psychiatric disorders in representative samples of individuals with autism and ID. Symptoms of autism and psychiatric disorders have been confounded. PAC, a conceptually analysed and validated screening instrument, was used. AIMS: Assess prevalence of psychiatric disorders in individuals with intellectual disability only (ID-only) and with combination of autism and ID (autism). Sixty-two (autism) and 132 (ID-only) participants were screened for psychiatric disorders with the Psychopathology in Autism Checklist (PAC); included general adjustment problems (GAP), and severe adjustment problems (SGAP) in one county in Norway. Psychosis, depression, anxiety, and OCD were addressed. Both SGAP and a high psychiatric disorder score were required to screen a psychiatric disorder. "Diagnostic overlap" was defined as more than one psychiatric disorder concurrent with autism. Psychiatric disorders and SGAP were found to be high both in the autism (53.2%) and ID-only group (17.4%). More than 50% of the autism and approximately 20% of ID-only group had SGAP. The differences were significant. The autism-psychiatric disorder interaction was significant. The largest differences between the prevalence in the autism and the ID-only group were shown in individuals with anxiety. The majority of the individuals in both study groups were afflicted with more than one psychiatric disorder. About 60% were found to have more than one disorder. The individuals with more severe psychiatric symptoms had higher degrees of diagnostic overlap. Having an intellectual disability seem to imply high risk for developing adjustment problems, and it seems especially difficult for individuals with autism to master every-day challenges.
Research in developmental disabilities, 2010 · doi:10.1016/j.ridd.2010.04.009