Some individuals come for first diagnosis in adulthood, perhaps prompted by the diagno- sis of autism in a child in the family or a breakdown of relations at work or home. Obtaining de- tailed developmental history in such cases may be difficult, and it is important to consider self- reported difficulties. Where clinical observation suggests criteria are currently met, autism spectrum disorder may be diagnosed, provided there is no evidence of good social and com- munication skills in childhood. For example, the report (by parents or another relative) that the cation skills throughout childhood would rule out a diagnosis of autism spectrum disorder; however, the absence of developmental information in itself should not do so.
Manifestations of the social and communication impairments and restricted/ repeti- tive behaviors that define autism spectrum disorder are clear in the developmental period.
In later life, intervention or compensation, as well as current supports, may mask these dif- ficulties in at least some contexts. However, symptoms remain sufficient to cause current impairment in social, occupational, or other important areas of functioning.
The best established prognostic factors for individual outcome within autism spectrum disorder are presence or absence of associated intellectual disability and language impair— ment (e.g., functional language by age 5 years is a good prognostic sign) and additional mental health problems. Epilepsy, as a comorbid diagnosis, is associated with greater in- tellectual disability and lower verbal ability.
Environmental. A variety of nonspecific risk factors, such as advanced parental age, low birth weight, or fetal exposure to valproate, may contribute to risk of autism spectrum dis- order.
Genetic and physiological. Heritability estimates for autism spectrum disorder have ranged from 37% to higher than 90%, based on twin concordance rates. Currently, as many as 15% of cases of autism spectrum disorder appear to be associated with a known genetic mutation, with different de novo copy number variants or de novo mutations in specific genes associated with the disorder in different families. However, even when an autism spectrum disorder is associated with a known genetic mutation, it does not appear to be fully penetrant. Risk for the remainder of cases appears to be polygenic, with perhaps hun- dreds of genetic loci making relatively small contributions.
Cultural differences will exist in norms for social interaction, nonverbal communication, and relationships, but individuals with autism spectrum disorder are markedly impaired against the norms for their cultural context. Cultural and socioeconomic factors may affect age at recognition or diagnosis; for example, in the United States, late or underdiagnosis of autism spectrum disorder among African American children may occur.
Autism spectrum disorder is diagnosed four times more often in males than in females. In clinic samples, females tend to be more likely to show accompanying intellectual disabil- ity, suggesting that girls without accompanying intellectual impairments or language delays may go unrecognized, perhaps because of subtler manifestation of social and com- munication difficulties.
Functional Consequences of Autism Spectrum Disorder
In young children with autism spectrum disorder, lack of social and communication abil- ities may hamper learning, especially learning through social interaction or in settings with peers. In the home, insistence on routines and aversion to change, as well as sensory sensitivities, may interfere with eating and sleeping and make routine care (e.g., haircuts, dental work) extremely difficult. Adaptive skills are typically below measured IQ. Ex- treme difficulties in planning, organization, and coping with change negatively impact academic achievement, even for students with above-average intelligence. During adult- hood, these individuals may have difficulties establishing independence because of con- tinued rigidity and difficulty with novelty.
Many individuals with autism spectrum disorder, even without intellectual disability, have poor adult psychosocial functioning as indexed by measures such as independent living and gainful employment. Functional consequences in old age are unknown, but so- cial isolation and communication problems (e.g., reduced help-seeking) are likely to have consequences for health in older adulthood.