Symptom Profile and Mental Health Conditions in Older Adults with Autism Spectrum Disorder (ASD)

Background: Although Autism Spectrum Disorder (ASD) is a lifelong condition, few studies have examined age-related changes in symptom profile. This is important, as the prevalence of ASD in older adults (50 years +) can be expected to increase with an aging population. To improve service provision for older adults, there is first a need to assess whether ASD symptomatology changes with age and if co-occurring mental health conditions influence presentation.

Objectives: To conduct an exploratory analysis of ASD symptomatology and co-occurring mental health conditions of younger (18-49 years) and older (aged 50-75 years) adults with ASD, compared with gender and age matched clinical controls without ASD (nil ASD).

Methods: A retrospective review of the medical records of 330 patients assessed for ASD at a specialist adult ASD diagnostic clinic between March 2003 and July 2017 identified 171 older adults (ASD N=108, Nil ASD N= 63). A comparison sample of 159 younger adults (ASD N= 101, Nil ASD N= 58) attending the same clinic was randomly selected. The groups were balanced on diagnosis and gender (older: M:F= 124:47; younger M:F= 109:49). Patient clinical records included the Autism Spectrum Quotient (AQ: self-report and informant), Autism Diagnostic Observation Schedule Generic and 2^nd Edition (ADOS-G/2), Hospital Anxiety and Depression Scale (HADS) and clinician identified current diagnoses (ICD-10). ANOVA and Chi-square analyses examined the effects of diagnosis (ASD vs nil ASD) and age (younger vs older), on autism symptoms (self-report, informant and clinician rated) and co-occurring diagnoses (number and type). Post-hoc correlation analyses were used where appropriate.

Results: There were significant main effects of diagnosis (ASD > nil-ASD) on the AQ [F(1,119)=472.64, p=.02] and social impairments [F(1,227)=121.23, p<.001], communication impairments [F(1,227)=96.10, p<.001] and repetitive and stereotyped behaviours on the ADOS-G/2 [F(1,224)=16.09, p<.001]. There was a significant main effect of age (older > younger) on social and communication impairments on the ADOS-G/2 [F(1,227)=70.39, p<.001, (F(1,227)=96.10, p<.001, respectively]. The diagnosis by age interaction was significant [F(1,227)=15.64, p<.001], revealing an age-related decline in communication difficulties and increase in social interaction impairments in ASD. There were no differences in the number of adults with mental health conditions (other than ASD). However, older adults were more likely to have anxiety and depression [χ2(1) = 6.31, p = .01, χ2(1) = 6.17, p = .01, respectively], whereas younger adults were more likely to have ADHD, [χ2(1) = 4.32, p = .04], regardless of diagnostic group. Older adults showed significant associations between social interaction impairments and self-rated HADS anxiety and depression scores [r = .31, p =.04 and r = .42, p < .001 respectively].

Conclusions: With increasing age in ASD, communication abilities improve but social interaction difficulties persist and worsen. Symptoms of anxiety and depression appear to contribute to greater impairment in older adults with ASD. More work is needed to confirm our findings and establish whether better identification and treatment of mental health conditions in older people with ASD will improve quality of life.