World Autism Month: Comorbidities in Adult Autism
A quarter of the general population have problems with their mental health at some point in their life. IN autistic people, this number is much higher with nearly 80% of adults with autism experiencing mental health issues during their lives.
Autism may co-occur with a number of physical and mental health difficulties. The prevalence is much higher for a range of conditions.
Anxiety disorders were diagnosed in 20.1% of autistic adults compared with 8.7% of population without autism in one study (Nimmo-Smith et al, 2019). Other studies suggest even 50% prevalence of anxiety symptoms in a group with autism (Lugnegard et al, 2011). In this study, from the spectrum of anxiety disorders the most commonly reported comorbidities were: social anxiety disorder (22%), generalised anxiety disorder, GAD (22%), agoraphobia (15%), panic disorder (13%) and obsessive-compulsive disorder, OCD (7%).
Hollocks with colleagues in his metanalysis estimated lifetime prevalence in autistic adults: social phobia -20%, OCD – 7%, GAD – 4%, agoraphobia – 4% (Hollocks et al, 2018).
According to research nearly 70% of autistic people had experienced at least one episode of major depression (Lugnegard et al, 2011). The prevalence of depressive disorders among individuals with autism was reported in several studies, which ranged from 1.47% to 54% (Hossain et al, 2020). Lifetime prevalence in other study was estimated to be 10% (Hollocks et al, 2018).
Study suggests that in an outpatient sample of adults with autism, 6% of the patients could have current diagnosis of bipolar illness (Joshi et al, 2013). However, the rates of lifetime bipolar disorder could be higher for autism (25% lifetime prevalence), compared to non-autistic adults (13% lifetime prevalence).
People with autism are 3 times more likely to develop schizophrenia. Lugo Marin with colleagues estimated pooled prevalence of psychotic illness among adults with autism, in their metanalysis, at 6.4% (Lugo-Marin et al, 2018). Other studies suggested significantly higher prevalence of schizophrenia in individuals with autism than in controls, and the prevalence of autism in individuals with schizophrenia ranged from 3.4 to 52% (Zheng et al, 2018).
In large dataset reviews transgender and gender-diverse individuals were 3.03 to 6.36 times more likely to be autistic than were cisgender individuals (Warrier et al, 2020). Other research, employing diagnostic criteria for autism, suggested a prevalence of 6–26% in transgender populations, higher than the general population, but no different from individuals attending psychiatry clinics (Thrower et al, 2020).
The reviewed studies showed that, on average, 4.7% of patients with certain eating disorder diagnoses (anorexia nervosa -AN; bulimia-BN; binge eating disorder -BED) received diagnosis of autism. For comparison large National Epidemiologic Survey in US estimates prevalence of lifetime AN, BN, and BED were 0.80%, 0.28% and 0.85% respectively (Udo et al, 2018).
Other study suggested a prevalence of 7.9% of eating disorder symptoms among autistic outpatient individuals, with anorexia and binge eating disorder being the most frequent (Karjalainen et al, 2016).
In a systematic review conducted by Arnevik and colleagues on patients with autism and substance use disorder it was reported that the prevalence rates ranged widely, from 0.7% to 36%, and most studies involved highly selected samples. Such inconsistencies limit the comparisons between studies and render it difficult to establish an overall rate for the co-occurrence of autism and substance use disorder. No systematic prevalence studies of non-biased samples have been published (Arnevik et al, 2016).
Attention deficit/hyperactivity disorder(AD/HD)
Research combining data from multiplesources and analysed using meta-regression reported a worldwide-pooled estimate of 5.29–7.2% in children (Thomas et al, 2016), 2.5% in adults (Simon et al, 2009) and between 2.8% in older adulthood (Michielsen et al, 2012) in population without autism.
However, study by Lugnegard found prevalence of ADHD among autistic population at 30% (Lugnegard et al 2011) and meta-analyse by Lai found overall pooled prevalence estimates of 28% (95% CI 25–32) (Lai et al, 2019).
Intellectual disability (ID) and autism are two neurodevelopmental conditions noted to have a high degree of overlap and co-occurrence. Historically, symptoms of ID were reported to co-occur in approximately 70% or more of those with autism; however, the rate of co-occurrence is now believed to be around 32% (Bilder et al, 2013; Jill et al, 2020). Additionally several genetic conditions would present with significantly higher rate of autistic features, e.g. tuberous sclerosis complex or Fregile-X.
Prevalence of epilepsy in the general population is between 1 and 2%, whilst general estimates suggest a prevalence of ~25–30% in individuals with autism (Parmeggiani et al, 2010).
Autism has been found to be associated with diverse sleep alterations (Baglioni et al, 2016). Specifically it was correlated with both sleep discontinuity and shorter duration of REM sleep. From previous meta-analyses, it was found that overall pooled prevalence estimates of 12% (95% CI 10-15) for sleep–wake disorders (Lai et al, 2019).
Large population-based studies found that individuals with autism present more often with gastrointestinal problems (34.7%) than neurotypical individuals, where most complaints concerned, with statistical difference, constipation, diarrhoea and oesophageal reflux (Croen et al, 2015).
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- Gillan Drew, An Adult with an Autism Diagnosis: A guide for the Newly Diagnosed. Jessica Kingsley Publishers.
- Jeanette Purkins, Emma Goodall, Jane Nugent, The Guide to Good Mental Health on the Autism Spectrum. Jessica Kingsley Publishers.
- Lee A. Wilkinson, Overcoming Anxiety and Depression on the Autism Spectrum : A Self-Help Guide Using CBT. Jessica Kingsley Publishers.
- Luke Beardon, Autism and Asperger Syndrome in Adults. Sheldon Press.
- Matt Tincani, Andy Bondy, Autism Spectrum Disorders in Adolescents and Adults: Evidence-based and promising Interventions. Guilford Press.
- Valerie Gaus, Living Well on the Spectrum: How to Use Your Strenghts to Meet the Challanges of Asperger Syndrome/High-Functioning Autism. Guilford Publications.