Diagnosis - PSY2004

Genetically defined conditions are diagnosed using

Biological Testing

Genetically defined conditions e.g.

Down Syndrome

Williams Syndrome

Down Syndrome testing

Prenatal: Combined blood test + nuchal translucency scan, followed by amniocentesis if high-risk.

Postnatal: physical characteristics + genetic testing for an extra chromosome 21.

Williams Syndrome testing

Confirmed via genetic testing (FISH test for ELN gene deletion).

Behaviourally defined conditions require

Clinical interviews

Behavioural observations

Standardised questionnaires and rating scales

Use of diagnostic manuals (DSM-5, ICD-11)

ADHD DSM-5

Must show 6+ symptoms (or 5+ if age 17+) for at least 6 months, in two or more settings, and inappropriate for developmental level.

Inattention symptoms can include

Careless mistakes, difficulty sustaining attention, easily distracted, forgetful, avoids tasks requiring sustained mental effort.

Hyperactivity symptoms can include

Fidgeting, difficulty remaining seated, excessive talking, interrupting, blurting answers, "on the go" behaviour.

Autism Spectrum Condition DSM-5

Social Communication Deficits + Restricted and repetitive behaviours

Symptoms in both domains, present early in development, cause functional impairment.

Social Communication Deficits

Impaired social-emotional reciprocity

Poor non-verbal communication

Difficulty developing and maintaining relationships

Restricted and Repetitive Behaviours

Stereotyped movements or speech

Insistence on sameness, inflexible routines

Highly fixated interests

Sensory sensitivities (hyper/hyporeactivity)

At least 2 required

Techniques for screening ASC

Questionnaires

Infant-siblings approach

fNIRS

EEG

Eye tracking

Questionnaires

M-CHAT (Modified Checklist for Autism in Toddlers): Used for toddlers aged 16-36 months.

High predictive value but not autism-specific — can detect general developmental delays.

Infant-Sibling Approach

Younger siblings of autistic children have a higher risk (~20%) of ASC.

Studies children as young as 4-6 months to find early indicators.

fNIRS (functional near-infrared spectroscopy)

Measures brain oxygenation.

Infants with higher ASC risk show reduced response to social stimuli in the temporal cortex.

EEG

Detects atypical brain connectivity in high-risk infants as early as 12 months.

Eye Tracking

Measures gaze patterns. Some autistic toddlers show stronger preference for geometric patterns over social stimuli.

Limitations of ASC screening techniques

Techniques reveal group differences but lack predictive power at the individual level.

Heterogeneity in ASC presentation makes it difficult to identify a universal biomarker.

ASC Prevalence

~1 in 100 in UK (9.8/1000)

ADHD Prevalence

Similar to ASC

ASC trends

Rise from 1 in 88 (2008) to 1 in 58 (2014) in US CDC data

Due to better awareness, reduced stigma, changes in diagnostic criteria

ADHD trends

Similar increase in prevalence to ASC

Improved recognition in girls

Better diagnostic tools

Awareness of prenatal/environmental risks