> To meet diagnostic criteria for ASD according to DSM-5, a child must have persistent deficits in each of three areas of social communication and interaction (see A.1. through A.3. below) plus at least two of four types of restricted, repetitive behaviors (see B.1. through B.4. below).

Example (A.1):

> Deficits in social-emotional reciprocity, ranging, for example, from abnormal social approach and failure of normal back-and-forth conversation; to reduced sharing of interests, emotions, or affect; to failure to initiate or respond to social interactions

The medical diagnostic criteria, despite using technical language, are still vague: "deficits in..." has a wide interpretation. Furthermore, "at least two of the four" permits two people diagnosed with autism to have different symptoms: one child may only have limited interests and insistence on sameness, while another may only have "stereotyped" motor movements and hypersensitivity (and the specific interests, "stereotyped" behaviors, and hypersensitive stimuli can vary).

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Essential (Required) Features:

Persistent deficits in initiating and sustaining social communication and reciprocal social interactions that are outside the expected range of typical functioning given the individual’s age and level of intellectual development.

Specific manifestations of these deficits vary according to chronological age, verbal and intellectual ability, and disorder severity.

Manifestations may include limitations in the following:

Understanding of, interest in, or inappropriate responses to the verbal or non-verbal social communications of others.

Integration of spoken language with typical complimentary non-verbal cues, such as eye contact, gestures, facial expressions and body language.

These non-verbal behaviours may also be reduced in frequency or intensity.

Understanding and use of language in social contexts and ability to initiate and sustain reciprocal social conversations.

Social awareness, leading to behaviour that is not appropriately modulated according to the social context.

Ability to imagine and respond to the feelings, emotional states, and attitudes of others.

Mutual sharing of interests.

Ability to make and sustain typical peer relationships.

Persistent restricted, repetitive, and inflexible patterns of behaviour, interests, or activities that are clearly atypical or excessive for the individual’s age and sociocultural context.

These may include:

Lack of adaptability to new experiences and circumstances, with associated distress, that can be evoked by trivial changes to a familiar environment or in response to unanticipated events.

Inflexible adherence to particular routines; for example, these may be geographic such as following familiar routes, or may require precise timing such as mealtimes or transport.

Excessive adherence to rules (e.g., when playing games).

Excessive and persistent ritualized patterns of behaviour (e.g., preoccupation with lining up or sorting objects in a particular way) that serve no apparent external purpose.

Repetitive and stereotyped motor movements, such as whole body movements (e.g., rocking), atypical gait (e.g., walking on tiptoes), unusual hand or finger movements and posturing.

These behaviours are particularly common during early childhood.

Persistent preoccupation with one or more special interests, parts of objects, or specific types of stimuli (including media) or an unusually strong attachment to particular objects (excluding typical comforters).

Lifelong excessive and persistent hypersensitivity or hyposensitivity to sensory stimuli or unusual interest in a sensory stimulus, which may include actual or anticipated sounds, light, textures (especially clothing and food), odors and tastes, heat, cold, or pain.

The onset of the disorder occurs during the developmental period, typically in early childhood, but characteristic symptoms may not become fully manifest until later, when social demands exceed limited capacities.

The symptoms result in significant impairment in personal, family, social, educational, occupational or other important areas of functioning.

Some individuals with Autism Spectrum Disorder are able to function adequately in many contexts through exceptional effort, such that their deficits may not be apparent to others.

A diagnosis of Autism Spectrum Disorder is still appropriate in such cases.