ASD and ID: Results from a National Study of ID of Genetic Origin

Background: Intellectual disability (ID) is characterised by significant limitations in cognitive functioning and adaptive behaviour. Many people with ID experience significant behavioural difficulties or mental health problems. IMAGINE-ID, is a recently established national UK study of psychiatric risk in ID of known genetic origin, with up to 10,000 participants. Here, we investigate the association between ID and ASD in the general population, and the prevalence of comorbidities including Anxiety Disorders, Disruptive Behaviour Disorders (DBD), Attention-Deficit/Hyperactivity Disorder (ADHD) and Tic Disorders.

Objectives: In the initial phase of this program, our focus has been on children (4-18 years) with ID that is associated with pathogenic Copy Number Variants (CNV), ascertained by NHS Regional Genetics Centres. By means of online/in-person phenotyping, we aimed to assess the prevalence of ASD, and contrast psychiatric comorbidities in those with and without ASD.

Methods: Over 900 participants with ID of genetic cause confirmed by microarray have so far been recruited into IMAGINE-ID. 651 assessments have been completed and 330 completed assessments have been clinically rated to date (over 1000 by May 2017). A standardized psychiatric interview, the Development and Wellbeing Assessment (DAWBA), is administered to caregivers; this generates probability scores for DSM-5 rated psychiatric symptomatology, including ASD. The DAWBA has been used in the UK’s national studies of child psychiatric adjustment. Genetic aetiology has been established: i) by microarray analyses (UK NHS accredited laboratories, with array resolutions typically 200kb); ii) aetiological SNV identified from the UK Deciphering Developmental Disorders survey.

Results: 31% of participants met criteria for a diagnosis of ASD. The male: female ratio in those with ASD was 3:1 but in the non-ASD group the sex ratio was equal. Mean age overall was 8.9 years (SD=3.8, range 4-18 years), with no significant differences in age, estimated mental age or language age between children with and without ASD. Participants with ASD were significantly more likely to meet DSM-5 criteria for an additional mental health disorder (36% vs 19%; p = 0.00) especially Anxiety Disorders (15% vs. 6%, p = 0.01), and Tic Disorders (4% vs. 1%, p=0.04). There were no significant group differences in the prevalence of ADHD or DBD.

The Everyday Feelings Questionnaire (EFQ) measures impairment in caregiver emotional adjustment, and was completed by all participant parents. EFQ scores were higher for both ASD/non-ASD groups than the general population. Impairment was significantly greater in parents of children with ID+ASD (M=18.7 vs 15.9; p=0.00).

Conclusions: IMAGINE-ID is the first study to systematically evaluate the prevalence of ASD in a national cohort of children with ID of known genetic origin. A higher proportion of participants in IMAGINE ID display clinically significant ASD traits than identified in national UK studies (using the DAWBA) with children with ID of unknown aetiology. When associated with ASD, children with ID were more likely to have additional psychiatric comorbidities, especially Anxiety Disorders and Tic Disorders. The emotional impact of caring for a child with ID is increased in the presence of comorbid ASD.