Autism Spectrum Disorders in Adulthood

Symptoms, diagnosis, and treatment

Background: The negative effect of autism spectrum disorders (ASD) persists into adulthood, with impacts on social interactions and occupational development. This article reviews the current status of clinical aspects of ASD in adulthood on the basis of ICD-11.

Methods: A selective search of PubMed and other relevant publications on ASD focused on changes in ICD-11 and on prevalence, symptoms, diagnosis, treatment, and prognosis.

Results: The global lifetime prevalence of ASD is around 1%. A number of recent studies have concentrated on behaviors termed “camouflaging” (disguising symptoms typical of autism) and “stimming” (use of repetitive self-stimulation), which affect the mental health of those concerned. Standardized diagnostic instruments are available, but the data on validity in adulthood and on applicability are limited. Gestures, eye contact, facial expressions, social closeness, and reciprocity play particularly important roles in diagnosis. German-language treatment manuals lack randomized controlled studies: a validated treatment strategy is currently available only in English. Investigation of the prognosis showed limitation of occupational perspectives (54% unemployment in the study sample) and 2.9 times higher mortality compared to the general population.

Conclusion: Individual treatment goals should be set, taking account of any coexisting psychiatric disorders. The process of diagnosis remains clinical, using standardized instruments. Further improvement of diagnostic and therapeutic instruments for adult ASD is desirable.

Autism spectrum disorders are characterized by a notably reduced intuition for social interactions, unusual interests, and stereotypical behaviors (1). In adulthood, substantial restrictions to professional development and to developing interpersonal relationships are common (1). This article aims to provide an overview of what is currently clinically known about the symptoms, diagnostic evaluation, and treatment of autism spectrum disorders in adulthood.

Methods

We conducted a selective literature search in PubMed in November 2021, using the search terms “autism” and “Asperger syndrome” as well as “adult/adulthood” in combination with “prevalence”, “symptoms”, “hypersensitivity”, “diagnosis/diagnostic”, “therapy/treatment”; the search was updated in October 2022. Systematic reviews, meta-analyses, and randomized controlled trials were preferentially considered. Furthermore we consulted both S3 guidelines for ASD (diagnostic evaluation; therapy), relevant handbooks, and online publications from WHO and the German Federal Statistical Office that were available up to October 2022.

Prevalence

Exact numbers on the prevalence of ASD in adults in Germany and trends over the past 20 years do not exist. For the purpose of an orientation estimate of prevalence trends we interrogated the Information System of the Federal Health Monitoring database using the following criteria:

• Autism
• Clinical sample of inpatient treatment cases
• All lengths of stay of patients aged 20–50
• Diagnoses: early childhood autism, atypical autism, and Asperger’s syndrome.

The data interrogation found for 2000 a total of 124 treatment cases; by 2020 this had risen to 635 cases (2). This corresponds to an increase by a factor of five over this time period.

Two systematic reviews regarding ASD described for Europe prevalence rates of 0.38% (Germany) to 1.55% (Spain) and for the USA of 1.7–1.85% (3) and a global median prevalence of 1% (Europe 0.24–2.68%) (4). These reviews included mostly studies in children; only few studies included adults as hardly any data exist for this group. Prevalence rates reported 20 years ago were lower (including for Asperger’s syndrome, of about 0.25%) (5). One reason for this increase could be increased attention regarding ASD, with diagnostic investigation more common. But there are also indications that environmental factors are involved, such as ASD after valproate intake during pregnancy (6) and an older age of father or mother at the time of fertilization (7).

Changes in the ICD-11

The ICD-10 included in the chapter on pervasive developmental disorders the categorical diagnoses of early childhood autism and atypical autism, as well as Asperger’s syndrome (8). The crucial differential criterion to Asperger’s syndrome was delayed cognitive development and speech development in early childhood autism (8). It transpired, however, that the validity of the distinction of these diagnostic criteria was not satisfactory and that transitions are fluent. Numbers and the severity of autism symptoms varied within and between the diagnostic subgroups and the prognostic predictability of the subcategories was low (9). The ICD-11 therefore now includes in the chapter on neuronal developmental disorders in analogy to the DSM-V the diagnostic category of autism spectrum disorders on a dimensional basis (1), which enables further specification by means of the two characteristics of an intellectual development disorder and the degree of functional speech impairment (Table 1).

Table 1

Diagnostic criteria for autism spectrum disorders (ASD) according to the ICD-11 and diagnostic codes according to intellectual development and possible functional speech impairment

The previously separate symptom areas of difficulties in social interaction and communication were combined into one symptom area. Here too the separation was not valid—both areas have substantial overlap. Deficits in communication relate materially to social interaction and are not of a structural nature (vocabulary or grammar) (9). Furthermore, because of its frequent occurrence, hyper- or hyposensitivity to sensory stimuli was included as a diagnostically relevant symptom of ASD (9) (Table 2). In the ICD-11 the clinical severity across different phases of life is also described, including adulthood. The fact is mentioned that social difficulties in dyadic relationships can be better managed by compensation strategies than in group constellations and special interests can be useful professionally. The working environment should therefore be adapted to the person. Furthermore, mention is made of the fact that a first diagnosis in adulthood often happens after decompensation in the private or professional environment.

Table 2

Rates of changed sensitivities in the respective sensory modalities*

Symptoms

The symptom areas of ASD in the ICD-11 comprise two categories (Table 1) (1):

• Difficulties in social interaction/communication
• Limited areas of interest/repetitive behaviors including unusual sensory sensitivity.

The symptoms present typically from early childhood, are sustained, and lead to impairments in different areas of life—for example, in family, school, professional, or social environments.

Persons with ASD have a reduced intuition for social situations, do not recognize body language intuitively, and interpret language in a very concrete manner. In talks/chats they grasp the emotional level to an insufficient degree. Even though for their interlocutor, communication—for example during small talk—serves to shape the relationship, for persons with ASD the factual information level is of crucial importance.

Recently, the compensation of autistic characteristics—a conscious or unconscious behavior known as camouflaging or masking—has been studied in a systematic manner. A unified operationalization of this concept does not exist to date. Often, however, this is understood to be the use of specific behaviors and cognitive strategies that autistic persons deploy to ensure that social deficits remain as invisible as possible. They have adapted to the non-autistic world so as to be less conspicuous and cope better within this world (10). Non-autistic behavior can be advantageous especially in conducting partner relationships or friendships, when completing education/training/apprenticeships, in employment, or to prevent exclusion. Camouflaging can, for example, include suppression of repetitive movements, forcibly sustained eye contact, or the use of learnt formulaic phrases (10). Cook et al (2021) in a systematic review analyzed 18 studies of camouflaging in adults with ASD (10). Nine of the studies analyzed an association with sex:

• In five studies, women with ASD deployed camouflaging more often than men with ASD
• One study confirmed stronger camouflaging in a non-binary gender identity compared with male sex
• Three studies did not show any association.

An association with camouflaging and mental wellbeing was investigated in 10 of the studies. Eight studies showed increased depression, anxiety, and a heightened perception of stress for a higher degree of camouflaging.

Repetitive behaviors comprised, for example, rocking and twisting movements, knuckle cracking, chewing items, or producing auditory stimuli such as whistling, humming, or clapping. This self stimulation has recently become known in science as “stimming.” In the past, these stereotypical behaviors in children were categorized as redundant and gradually reduced by training wherever possible. Recent studies in which adults with ASD were questioned in an interview or by means of a questionnaire showed consistently that these behaviors have an important self regulatory function (11, 12, 13): affected persons deploy self stimulation, initially often unconsciously, in order to regulate intense positive or negative emotional states, to soothe themselves, and to regain emotional control over themselves. In this setting, rhythm seems a helpful component in stimming, and focusing the attention on stereotypical behaviors results in a reduction in the perception of overly demanding stimuli. Such stimuli are among the crucial causes of the increased stress experience in ASD and can be externally caused—for example, in the form of noise or other sensory stimuli—or they are of an intrinsic nature—for example, in the sense or debilitating thoughts and feelings (13). Those affected described as problematic the fact that stimming is often socially undesirable (11, 13), since repetitive noises or movements are experienced by others as odd or disturbing. Suppressing stimming, however, leads to further stress. Affected persons have reported improved acceptance of stimming after explaining its function (13).

Sensory sensitivities in ASD manifest, for example, as hypersensitivities towards auditory or tactile stimuli, so that ticking clocks, humming electrical devices, or light touches can be experienced as disagreeable or burdensome. Studies have described that in 18–69% of people with ASD who are affected have hyperacusis (14). The underlying causes are heterogeneous and can, among others, also result in a reduced/delayed stapedius reflex, anatomical particularities of the semicircular canals of the ear, or abnormal neuronal connections in the olivary nuclei (14). The other sensory modalities too can be affected by changed sensitivity, visually, for example, in the form of heightened contrast perception or an extended visual field (15). Olfactorily or gustatorily, hypersensitivity or hyposensitivity may be present (15). Table 2 provides an overview of data on the rates of changed sensitivity of the sensory modalities, collected by Leekam et al (2006) in 200 autistic children and adults (categorized into four groups by IQ and age) (16). In 64–83% more than one sensory modality was affected. The rates of changed auditory sensitivities was lower in this study than in the study reported by Danesh et al (14).

Diagnosis

The diagnosis of ASD is made clinically. To date no valid methods exist for confirming the diagnosis technically or biologically. The diagnostic investigation is done mostly in specialized centers and includes a detailed psychiatric examination and medical history regarding the diagnostic criteria in childhood and adulthood. The Autism Diagnostic Interview-Revised (ADI-R) (17) and the diagnostic observation scale for autistic disorders (ADOS-2) (18) are still the diagnostic gold standard. The ADI-R comprises 93 items and is preferably undertaken with the patient’s parents. Module 4 of the ADOS-2 was conceived for adults and included special interview questions and test questions. A study of 385 adolescents with ASD and 288 controls found by using machine learning that the isolated use of five test subgroups of the ADOS module 4 (gestures, eye contact, facial expressions, social approaches, reciprocity), with a sensitivity of 72% and a specificity of 87%, were comparable with the application of the entire test (19).

In the most recently published S3 guidelines for the diagnostic evaluation of ASD, neither of these two instruments is recommended, and nor are any of the other available standardized diagnostic interviews for use in adults, as there isn’t enough study evidence for their diagnostic validity, among others (20). The current UK guidelines from the Institute for Health and Care Excellence (NICE) (21) do, however, recommend several standardized interviews and instruments for diagnosing ASD in adults (Table 3).

Table 3

Recommendations of the NICE guideline (21) for instruments for diagnosing ASD in adulthood and available quality criteria*

A third-party medical history should be taken from a person who experienced the affected person in childhood (for example, a parent or an older sibling). If available, comments from school reports or psychiatric preliminary reports are also helpful information sources. On contact, especially the lacking eye contact and lack of facial expression and a monotonous way of speaking may be conspicuous.

A physical exam should be added in order to, for example, ascertain low-grade ataxia or slight uncertainty in coordination as soft signs of ASD (22). Particularities of the facial skull (Fragile X syndrome: narrow, elongated face, prominent ears and forehead, in 20–30% ASD), height, and development of secondary sexual characteristics (Klinefelter syndrome; above average height, reduced body hair; in 11–12% ASD) can indicate syndromic autism (22). There are no precise data on the rates of syndromic disorders as a cause of ASD; according to estimates rates vary between 10% and 20% (22).

An exploration regarding psychiatric comorbidities should be carried out, especially depression (30–70%), anxiety disorders (45–56%), and attention deficit/hyperactivity disorder (ADHS) (30%) are common in ASD (22).

In terms of perspective/outlook, the development of objective methods to add to the diagnostic repertoire is important. In a study of 664 persons with and without ASD, differences were seen on MRI scans of the brain by means of machine learning and a specific neuronal atlas was developed. This atlas helps identify the brains of patients with ASD with a precision of 97±2% (23), although no prospective confirmation of this tool is available to date.

Therapy

The S3 guideline on the therapy of ASD (24) emphasizes that at the start of treatment, clear, individual therapeutic goals should be defined that can be geared towards the core symptoms of ASD as well as on comorbid psychiatric disorders. For adults with ASD without intellectual disability, group therapy for 3–6 months with 6–8 participants is recommended, which among others includes the following parameters (24):

• Discussions of situations in everyday life
• Training in small talk, conversational technique, and establishing contact
• Dealing with stress, emotions, and conflicts.

German-language manuals for psychotherapy in adults with ASD in a one-to-one setting (25) and group setting (26, 27), which also address the listed topics, exist (Table 4), but no randomized controlled trials (RCTs) have been published for these so far. The therapeutic concept “PEERS for young adults” (28), however, has been investigated in RCTs, but it is available in English only (Table 4). In adults patients with ASD and existing mental retardation, the treatment according to S3 guidelines should consist primarily of behavioral therapeutic training of everyday practical activities according to the current developmental state of the patient (24). In concrete terms this may mean, for example, practicing bodily hygiene, housework, or an activity in a workshop (24).

Table 4

Therapeutic interventions in autism spectrum disorders (ASD) in adulthood

Self help groups can also provide complementary support for affected persons.

A further important area is job support. Studies have shown that job application training, where job interviews are practiced in role play or in a virtual environment and small talk is rehearsed, and which conveys knowledge regarding finding and holding down a job, improve the success of job applications and result in placements in the first workplace (24, 29, 30) (Table 4).

Thus far, no medication exists for treating the core symptoms of ASD. The S3 guidelines recommends in pronounced stereotypical behaviors to give antipsychotic drugs, such as risperidone or aripiprazole (24) for a limited period of a few weeks. The evidence for use in adults is poor, however (effects size risperidone: standardized mean difference [SMD]=0.97; 95% confidence interval [0.21; 1.74]; effect size of aripiprazole is available only for children/adolescents: SMD=0.48; [0.26; 0.70]) (31). For comorbid anxiety disorders or depressive disorders, selective serotonin reuptake inhibitors (SSRIs) can be used (24) and for comorbid ADHD, methylphenidate or atomoxetine (24).

Oxytocin is an active substance that has been investigated in studies for several years for its potential future clinical application (for example, administered via a nasal spray). Data continue to be heterogeneous, however. Some studies showed short-term unsustained improvements in social interaction, recognition of emotions, and repetitive behaviors, whereas other studies did not show any significant effect (32). The existing data therefore do not justify the use of oxytocin for the treatment of ASD in routine clinical practice.

Prognosis

Intellect is a decisive factor in the prognosis in ASD. Intellectual disability mostly requires comprehensive support, a structured environment, and carers (22). Furthermore, a therapeutic living environment may be indicated. In high functioning ASD, impairments often affect the achievement of age-typical life goals. Often, persons have an above-average educational attainment, but no corresponding employment (22). In the authors’ own studies of adults patients with ASD (aged 20–62 years, mean/average 36.5 years), 46 of 50 persons with ASD under study were in employment, 28% lived in a partner relationship, and 20% had children (33).

A Swedish cohort study of 27,122 persons with a diagnosis of ASD between 1987 and 2009 showed a higher mortality for persons with ASD than for the general population (mortality general population 0.91% versus persons with ASD 2.60%), with mortality increased in almost all causal diagnostic categories (34).

This illustrates the urgent need for specific treatments and support for adults with ASD.

Conclusions

The estimated global median prevalence of ASD is 1%. The diagnosis is still made clinically, by using standardized instruments. The treatment comprises primarily psychotherapeutic interventions. The prognosis in adults with ASD with regard to gainful employment and development of partner relationships is associated with limitations; mortality is higher than in the general population.

Conflict of interest statement
The authors declare that no conflict of interest exists.

Manuscript received on 15 February 2022, revised version accepted on 14 November 2022.

Translated from the original German by Birte Twisselmann, PhD.

Corresponding author
PD Dr. med. Mandy Roy
Autismus-Ambulanz
Asklepios Klinik Nord Ochsenzoll
Langenhorner Chaussee 560
22419 Hamburg, Germany

Cite this as:
Roy M, Strate P: Autism spectrum disorders in adulthood—symptoms, diagnosis,
and treatment. Dtsch Arztebl Int 2023; 120: 87–93.
DOI: 10.3238/arztebl.m2022.0379

cme plus

This article has been certified by the North Rhine Academy for Continuing Medical Education. Participation in the CME certification program is possible only over the internet: cme.aerzteblatt.de. The deadline for submission is 9 February 2024.

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