Article first published October 2014; updated March 2021


First described by Kanner in the early 1940’s,1 Autism Spectrum Disorders (ASDs) are characterised by a triad of qualitative impairments in communication, social interaction and rigid/repetitive behavioural patterns. As a group of complex neuro-developmental disorders (encompassing autistic disorder, Asperger’s syndrome and pervasive developmental disorder, unspecified), ASDs are usually diagnosed in childhood, with an onset typically before the age of 3.2 Why then should their diagnosis be of interest to old age specialists?

There are many reasons why older adults with ASDs were not diagnosed in early life. Firstly, autism and Asperger’s Syndrome are relatively ‘modern’ diagnoses e.g. they did not appear in the World Health’s Organisation International Classification of Diseases until 1992 (autism appeared in Diagnostic and Statistical Manual-III in 1980, with Asperger’s syndrome appearing in Diagnostic and Statistical Manual-IV in 1994). Even then, knowledge of their persistence after childhood was limited. Secondly, we do not have validated screening and diagnostic ASD instruments for the assessment of older adults. Finally, and importantly, psychiatric comorbidity, which is very common,3 may mask an ASD. Perhaps as a reflection of the above, referrals to old age psychiatry for suspected ASD are rare.4

Prevalence of autism spectrum disorders in older adults

One UK study revealed that the prevalence of ASDs were relatively stable in older age groups: 1.1% of 14-44 year olds, 0.9% of 45-75 year olds, and 0.8% of those aged 75 and older.5, 6 However, it is thought that these results may underestimate the prevalence of ASDs in older adults because the study did not adequately sample from individuals with intellectual disability, and those in institutional settings i.e. samples where one would expect a high prevalence.Moreover, although some people’s autism is diagnosed in childhood, for every three known cases, there are two individuals without a diagnosis who might need assessment, support and interventions for autism at some point in their lives.8

Why is making a diagnosis important?

ASD can be easily missed in older adults, particularly in those presenting with co-morbid psychiatric disorders, which can potentially result in iatrogenic damage.9 Particular problems may arise in identifying Asperger’s syndrome (sometimes referred to as high functioning autism), which can be misdiagnosed as depression, personality disorder, or a psychotic illness.

Missing a diagnosis of ASD not only leads to inadequate care, but can also result in inadequate recognition and treatment of comorbid mental and physical health problems. Even where older adults with ASD are receiving support (e.g. as result of a co-occurring psychiatric disorder, or learning disability), the support can break down if the ASD is not also identified and properly supported. Many adults who received their diagnosis later in life struggle to make sense of their earlier lives, and regret the opportunities and experiences they missed due to an undiagnosed ASD.10

When should I suspect a possible diagnosis of ASD?

During the psychiatric interview, a possible impairment in one or more of the three core areas of an ASD may become apparent – see Box 1 for examples. NICE guidance recommends that for adult patients without a moderate to severe learning disability, one’s clinical suspicion is supported by use of the Autism-Spectrum Quotient 10- items (AQ-10) screening tool11 (see Box 2) . The AQ-10 is a self-report questionnaire, and if an individual scores 6 or more, a comprehensive assessment for ASD should be offered. Currently however, there are no specific ASD screening instruments for older adults.



Box 1:      Consider the possibility of ASD, when one or more, of both A and B is present:




  • Persistent difficulties in social interaction                
  1. A limited interaction, which is aloof, indifferent, or unusual.
  2. The interaction is used to fulfil the patient’s needs only.
  3. The interaction is naïve or one-sided.         
  4. The patient seems to have difficulty in understanding unwritten ‘social rules’ e.g. judging how close to stand someone, or what’s an appropriate topic of conversation.
  • Persistent difficulties in social communication       
  1. Lack of responsiveness to others
  2. Little or no change in behaviour in response to different social situations.               
  3. Limited social demonstration of empathy
  4. Patient seems to have difficulty in understanding people’s gestures, facial expression or tone of voice
  5. Patient seems very literal, and sometimes struggle with jokes, metaphors, sarcasm, or common turns of phrase.
  • Rigid and repetitive behaviours, resistance to change or restricted interests


  • History of problems in obtaining or sustaining employment or education
  • Difficulties in initiating or sustaining social relationships
  • Previous or current contact with mental health or learning disability services
  • A history of a neurodevelopmental condition (including learning disabilities and attention deficit hyperactivity disorder) or mental disorder






Box 2  Autism Spectrum Quotient – 10 items (AQ-10): a quick referral guide for adults with suspected autism who do not have a learning disability


Please tick one option per question only

Definitely agree

Slightly agree

Slightly disagree

Definitely disagree


I often notice small sounds when others do not






I usually concentrate more on the whole picture, rather than on small details






I find it easy to do more than one thing at once






If there is an interruption, I can switch back to what I was doing very quickly






I find it easy to “read between the lines” when someone is talking to me.






I know how to tell if someone listening to me is getting bored






When I’m reading a story I find it difficult to work out the characters’ intentions






I like to collect information about categories of things (e.g. types of car, types of bird, types of train, types of plants etc.)






I find it easy to work out what someone is thinking or feeling just by looking at their face






I find it difficult to work out people’s intentions





  • Only 1 point can be scored for each question.
  • Score 1 point for Definitely or Slightly Agree on each of items 1,7,8 and 10.
  • Score 1 point for Definitely or Slightly Disagree on each of items 2, 3, 4, 5, 6, and 9.
  • If an individual scores more 6 or more, consider referring them for a specialist diagnostic assessment.


Making the diagnosis in later life

A clinical diagnosis of ASD is usually based on a psychiatric examination, which includes a detailed developmental history, normally provided by the patient’s parents. In older adults, obtaining such a developmental history may be impossible, either owing to the lack of informants, and/or because of significant recall bias e.g. owing to a long time-line, or potential cognitive impairment in the informant.

As many individuals with ASD have impaired insight into their disabilities,12 obtaining collateral histories from knowledgeable informants e.g. close relatives and carers, can enhance the accuracy of the diagnostic process.

For younger adults, NICE recommends that a formal ASD assessment is undertaken by multi-professional trained and competent specialists, who may support their work by using a formal assessment tool, such as the Autism Diagnostic Observation Schedule.11

In practice however, older adult services generally do not have access to such specialist teams (owing to age barriers), and none of the formal assessment tools have been validated for this age group.

Currently therefore, diagnosis in older adults remains a clinical one, based on identifying the core signs and symptoms of ASD, which have been present since childhood and have persisted into old age. This should be supported by collateral histories from close relatives/informants, and may (if available) include school reports.13

For the non-specialist, the operational diagnostic characteristics of the Diagnostic and Statistical Manual (DSM) may be more clinician-friendly. In the new DSM-V, the former diagnoses of autism, Asperger’s syndrome and pervasive developmental disorder, not otherwise specified, have been merged into a single unifying diagnosis – Autism Spectrum Disorder, the diagnostic criteria for which are outlined in Box 3.


Box 3. DSM-5 Criteria for Autism Spectrum Disorder


Currently, or by history, must meet criteria for A, B, C and D.




  • Persistent deficits in social communication and social interaction across contexts, not accounted for by general developmental delays, and manifest by all 3 of the following:
  1. Deficits in social-emotional reciprocity
  2. Deficits in non-verbal communicative behaviours used for social interaction
  3. Deficits in developing and maintaining relationships




  • Restricted, repetitive patterns of behaviour, interests, or activities as manifested by at least two of the following:
  1. Stereotyped or repetitive speech, motor movements, or use of objects
  2. Excessive adherence to routines, ritualised patterns of verbal or nonverbal behaviour, or excessive resistance to change
  3. Highly restricted, fixated interests that are abnormal in intensity of focus
  4. Hyper- or hypo-reactivity to sensory input or unusual interest in sensory aspects of environment




  • Symptoms must be present in early childhood (but may not become fully manifest until social demands exceed limited capacities)




  • Symptoms together limit and impair everyday functioning




Differential diagnoses of ASD in older patients

The presence of ASD can be masked by other psychiatric disorders, or by a normal or high intelligence. Moreover, ASD symptoms can have significant overlap with other disorders, examples of which are outlined in Box 4. It can be challenging to disentangle the social and communication problems associated with ASD, from the often complicated clinical picture in older adults, especially when developmental information is not available.


 Box 4:  Differential diagnoses


Differential parameter 


  • Detailed information about “premorbid” functioning is key; dementia is progressive (age on onset usually after 55-60 years), whereas ASD is a lifelong condition.
  • Consider an early fronto-temporal dementia, which can be difficult to differentiate from ASD; neuropsychological assessment and neuroimaging can be helpful here.



  • ASD can show overlap with the negative symptoms of schizophrenia, especially the disorganised type. Eliciting a history of decline in adolescence/early adulthood is important here.
  • Very late onset schizophrenia may resemble ASD, but its onset is later in life.


Anxiety Disorders

  • These are characterised by irrational cognitions. Communication and social skills should remain intact.

Obsessive Compulsive Disorder (OCD)

  • In OCD, obsessions and compulsions are unwanted, ego-dystonic, resisted and cause distress, whilst repetitive behaviours in ASD comforts the patient.

Personality Disorder

  • Higher functioning individuals with ASD may be considered as having avoidant, obsessive-compulsive, narcissistic or schizoid personality traits/disorder.  Early developmental data are key e.g. emergence of traits in adolescence/early adulthood may be more typical of a personality disorder, whereas early childhood impairment in imaginary play, socialising and restricted behaviours would be more typical of ASD. Where there is doubt, the use of in-depth personality profiling can be helpful15.


Interventions in older adults with ASDs

There is currently a dearth of knowledge in regard to what interventions are required or beneficial for older adults with ASDs.

NICE guidance for younger adults does not recommend pharmacotherapy in the management of core ASD symptoms,11 which should logically also extend to include older adults. Comorbid mental health symptoms and conditions (e.g. depression, anxiety etc.) should be identified and treated appropriately.

Psychosocial interventions focused on the core symptoms (e.g. improving social interaction), and on life skills, are recommended by NICE for younger adults. In an older population, one might postulate that similar interventions would also be of benefit, and could perhaps be provided by specialist day centres.

Health professionals should be aware that people with autism may experience and report pain differently to others. Difficulties with understanding feelings, with communication, and with insight, can make it challenging for people with ASD to recognise when they are unwell. This becomes more pertinent in older age, when ill health increases.

Carers should be offered an assessment of their own needs (personal, social and emotional), and supported in their caring role e.g. including emergency plans, respite care, advice on practical support and training, as well as future care planning.

Understanding the person’s level of functioning, the presence of physical and other mental health problems, as well as possible challenging behaviours, are key to creating an individual management plan. 


Clinical Case

Ms W, a single 65 year-old retired Caucasian lady, was referred by her GP for an assessment of a likely depressive episode. Her symptoms were one month of: frequent tearfulness, lack of appetite, insomnia, and anhedonia. Ms W lives with her mother, who is 90 years old, and who has a diagnosis of Alzheimer’s dementia. Ms W had recently stopped the mental health team from performing domiciliary visits for her mother. In the past, Ms W had been treated by her GP for depression, and had also self-treated with St. John’s Wort.

Background: Her niece revealed that Ms W always held very rigid rules and routines, which if broken, led to extreme agitation. As examples of her rigidity, Ms W would not sit on her sofa, as she regarded it as “new”, even though it was 10 years old. Similarly, she would make her elderly mother eat whilst standing over the sink, as to avoid any falling crumbs. Only family members, who held to her rules, were permitted to enter their home. Her mother’s memory problems were impacting on her ability to adhere to Ms W’s rules, and the visiting mental health team imposed on Ms W’s routines. Prior to our assessment, this had precipitated an episode of severe agitation, which resulted in Ms W’s arrest by the Police, and treatment with benzodiazepines in the Accident and Emergency department.

Her niece added that Ms W also struggled to verbalise emotions, or to respond to the emotional needs of others. Ms W did not appear to show interest in others, and as a result, was estranged from her family. She had always held repetitive manual labour posts, where she excelled in the work. However, Ms W struggled with the social environment of factory life, and walked out of one long-held post following a simple practical joke i.e. she would always place her coat on a particular hook, and her colleagues moved it to another one. Ms W never had a close friend, and was never in a personal relationship, preferring the company of animals to humans. She described animals as being “easier to understand”. She had fallen out with all of her neighbours, including a new neighbour who had played music on his radio while painting the exterior of his home. Ms W explained that she had always been very sensitive to sound, and also to touch. As a result of the latter, she had missed many medical screening appointments e.g. for breast and cervical cancer screening.

In this case, the chronic history of interpersonal difficulties, in combination with rigidity, inflexibility, lack of social reciprocity and bonding, led to a diagnosis of Pervasive Developmental Disorder, unspecified (ICD-10 code F84.9), and a co-morbid diagnosis of a moderate depressive episode. Ms W did not wish to undergo further assessment, as she felt she had no difficulties. The absence of a detailed developmental history prevented the assignment of a more specific ASD. Using DSM-V, Ms W met the diagnostic criteria for Autism Spectrum Disorder, code 299.0.



As a relatively recent group of disorders, ASD remains largely unknown to old age specialists. There exists a large and undiagnosed population of older adults with ASD, which is expected to increase substantially in the near future. As in our clinical case, the primary reason for referral to old age psychiatry may conceal an underlying ASD.

Healthcare professionals should therefore be alert for signs of a co-morbid ASD in their elderly patients. Whenever possible, a thorough developmental history should be taken, but when this is not feasible, collateral history should be sought for relevant information about long-standing behaviours. In day-to-day practice, it is likely that most cases of ASD in older people will be identified this way. Little if anything is known about the phenotype of ASD as individuals’ age, or about their specific medical, psychiatric and social needs, including the need for long term care. Research is needed to answer these crucial questions, not only to direct future clinical practice, but importantly, to improve the lives of older adults with ASDs.


Some helpful resources:

For patients and their families/carers:

  1. National Autistic Society - UK charity for people with autism spectrum disorder, and their families. They provide information, support and pioneering services, and campaign for people with autism
  1. Caring for someone with autism – Live Well – NHS Choices
  1. Patient information leaflets, and avenues of support

For clinicians:

  1. Autism: recognition, referral, diagnosis and management of adults on the autism spectrum. NICE clinical guideline.
  1. Research autism - UK charity exclusively dedicated to research into interventions in autism
  1. Autism Research Centre - researches biomedical causes of autism spectrum conditions, and develops new and validated methods for assessment and intervention. One can download the AQ-10 from this site also.


Dr. David O’Regan, Dr. Robert Tobiansky, Consultant Old Age Psychiatrist



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