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Impairment is present when:

• Occipitofrontal head circumference (OFC) is <3rd centile (microcephaly)
• A seizure disorder has been diagnosed not due to known postnatal influences
• Brain imaging shows convincing evidence of structural abnormalities associated with PAE (e.g. reduced overall brain size, agenesis or hypoplasia of the corpus callosum, reduced cerebellar, hippocampal or caudate volume) after other aetiologies excluded
• Significant neurological diagnoses otherwise unexplained, e.g. cerebral palsy, visual impairment or sensorineural hearing loss, when other causes have been excluded

Exclude other causes of microcephaly (familial, chromosomal, infection, other teratogens) and measure parental head circumference where possible. MRI is not required for diagnosis, but is recommended when clinically indicated. In infants and young children with all three sentinel facial features, microcephaly meets the CNS criterion for FASD with sentinel facial features.

Impairment is present when a composite score, or one or more major subdomain scores, is below the clinical cut-off on a validated test (e.g. Movement ABC-2, BOT-2, Beery VMI) for:

• Fine motor skills
• Gross motor skills
• Graphomotor skills (writing, drawing)
• Visual-motor integration

Tone, reflexes, balance, coordination, strength, and other neurological examination findings may be considered in combination with formal assessment.

Impairment is present when standardised tests show:

• Composite IQ or cognitive score below clinical cut-off
• A major subdomain score (verbal, nonverbal, or fluid reasoning) below cut-off
• A large and unusual discrepancy among major subdomain scores (base rate ≤3% of population, with the lower score ≥1 SD below the mean)

Children with FASD commonly have a spiky cognitive profile. They are strong in some areas, significantly impaired in others. Uneven profiles are characteristic and should not be dismissed.

Impairment is present when:

• Composite score on core language, receptive language, or expressive language is below clinical cut-off
• Multiple subtest scores on higher-level language skills are below cut-off (e.g. narrative comprehension, complex language)
• Large discrepancy between receptive and expressive language composites (base rate <3%, lower score ≥1 SD below mean)

Children may appear to understand but not follow through. This often reflects a gap between receptive and executive processing, not non-compliance.

Impairment is present when standardised scores in reading, mathematics, or written expression are below clinical cut-off, or when there is a significant discrepancy between cognitive ability and achievement (base rate <3%, achievement score ≥1 SD below mean).

The clinical team must confirm the child has had consistent access to academic instruction before recording a deficit in this area.

Impairment is present when:

• Composite score on overall memory, verbal memory, or visual memory is below clinical cut-off
• Large discrepancy between verbal and non-verbal memory (base rate <3%, lower score ≥1 SD below mean)

Working memory deficits are assessed under Executive Function, not Memory. Children may appear to have learned a rule or skill and then "forgotten" it. This is characteristic of FASD memory impairment.

In SIGN 156, attention is defined as sustained or selective attention and resistance to distractions. Inhibition, impulse control, and hyperactivity are assessed under Executive Function.

Direct assessment: Multiple subtest scores below cut-off on continuous processing tests or neuropsychological attention measures.

Indirect assessment: Converging evidence from clinical interview, questionnaire, file review, and direct clinical observation during testing.

A DSM-5 diagnosis of ADHD, inattentive or combined presentation, fulfils the criteria for severe impairment in attention. The hyperactive-impulsive presentation counts towards executive function instead.

FASD is frequently misdiagnosed as ADHD alone. Many children receive ADHD diagnoses and medication without recognition of the underlying PAE. Both conditions can coexist.

Executive function covers higher-level skills for organising and controlling thoughts and behaviours toward long-term goals. In SIGN 156 this includes:

• Working memory
• Inhibition and impulse control
• Hyperactivity
• Planning and problem solving
• Shifting and cognitive flexibility

Direct: Two or more subtest scores below cut-off on neuropsychological measures of executive function (e.g. BADS-C, NEPSY-II, D-KEFS). Indirect: Converging evidence from rating scales (e.g. BRIEF-2), clinical interview, file review, and direct observation.

If indirect measures show impairment but direct tests are normal, SIGN 156 gives significant weight to the indirect measures. Two or more standardised rating scales below cut-off (e.g. two observers) count as severe impairment.

There is no direct test. Severe impairment is present when the individual meets ICD-10 criteria for:

• Recurrent depressive disorder
• Separation anxiety disorder, elective mutism, social phobia, panic disorder, agoraphobia or generalised anxiety disorder
• Mixed anxiety disorders, or mixed anxiety and depressive disorder
• Conduct disorder or oppositional defiant disorder

Clinicians should formally confirm the criteria are met, not rely on clinical impression or rating scales alone.

Important SIGN 156 qualifier:

Affect dysregulation should only be attributed to PAE if it is long-standing. It should NOT be attributed to PAE if it is clearly a response to adverse life events (e.g. multiple foster placements) or is situationally specific.

Impairment assessed by:

• Direct (social communication): Score below cut-off on composite measure of social language, pragmatic language, or social communication skills
• Indirect (adaptive behaviour/social skills): Score below cut-off on global composite or major subdomain of a standardised caregiver rating scale or informant interview

For children and most adolescents, standardised caregiver ratings should be used. Observations and ratings should be gathered across environments. Parents report on behaviour at home, and teachers report on behaviour at school.

Meeting DSM-5 criteria for autism spectrum disorder or social (pragmatic) communication disorder on formal testing counts as severe impairment in this area. Conduct disorder or severe ODD provides supporting evidence only.

For adults without a consistent caregiver in the last 2 years, historical records and alternative interview methods may be used as a proxy.