Many individuals, clinicians and laypeople alike, read through the autism diagnostic criteria from the DSM-5 via the internet. However, most do not have access to or have never read through the details of the supplementary material included in the full manual.
The supplementary material explains some of the phrases and the intention of the criteria as written. For example, the criteria discuss that the deficits are "persistent" and seen "across multiple contexts." The symptoms "must be present in the early developmental period."
What does the supplementary material explain?
1. Must Be Present in the Early Developmental Period
Although the characteristics are present in the early child, the manual does not stipulate that the symptoms must be recognized and correctly labeled at that time.
Rather, the manual states that the symptoms "may not become fully manifest until social demands exceed limited capacities, or may be masked by learned strategies in later life" (pg 53). Also, "These symptoms are present from early childhood... (although) the stage at which functional impairment becomes obvious will vary according to the characteristics of the individual and his or her environment. Core diagnostic features are evident in the developmental period, but intervention, compensation, and current supports may mask difficulties in at least some contexts."
Additionally, page 56 includes the notation that first recognition of symptoms may occur in adulthood. "Some individuals come for first diagnosis in adulthood, perhaps prompted by the diagnosis of autism in a child in the family or a breakdown of relations at work or home."
Thus, the statement that the symptoms are present early in development is further explained by noting that the characteristics may not always be recognized during early development.
2. Impairments are Pervasive and Sustained (pg 53)
The manual further states on page 53 that "verbal and nonverbal deficits in social communication have varying manifestations, depending on the individual's age, intellectual level, and language ability, as well as other factors such as treatment history and current support." That is, although pervasive and sustained, the way that the social communication characteristics present is impacted by age and other factors.
The presentation of characteristics is also impacted by compensation and learning. "Adults who have developed compensation strategies for some social challenges still struggle in novel or unsupported situations and suffer from the effort and anxiety of consciously calculating what is socially intuitive for most individuals."
Also, "...It is typical for learning and compensation to continue throughout life" (pg 56).
3. The Symptoms are Seen Across Context
Although the intent of this statement is to make sure that only characteristics that are neurologically based are identified as autistic (as opposed to a child's reaction to one person or one situation exclusively). Some misunderstand this statement to suggest that the characteristics must appear the same in every situation.
However, the manual states that characteristics may look different in public than they are experienced in private, "Many adults with autism spectrum disorder without intellectual or language disabilities learn to suppress repetitive behavior in public (pg 54)." Also, supports and compensation can change the way characteristics appear in certain settings: "In later life, intervention or compensation, as well as current supports, may mask these difficulties in at least some contexts (pg 56)."
As seen in #1 above, the manifestation may vary depending on characteristics of the individual and the environment.
4. Diagnosis with Multiple Sources of Information
Also of note, the manual emphasizes that no one approach or source of information should be used in the diagnostic process. Rather than relying on one questionnaire or diagnostic interview, the assessment should be based on multiple sources of input.
Family history and self-report are important aspects of the assessment, in combination with clinician observations and questionnaires. Page 53 notes, "Diagnoses are most reliable and valid when based on multiple sources of information, including clinician's observations, caregiver history, and, when possible, self-report."
When individuals present for diagnosis In adulthood, "Obtaining detailed developmental history in such cases may be difficult, and it is important to consider self-reported difficulties. When clinical observation suggests criteria are currently met, autism spectrum disorder may be diagnosed..." Also, "The absence of developmental information in itself should not [rule out a diagnosis]" page 56.