Table 4.

Proposed clinical features of IRDS.

Core Symptoms and Signs	Potential Triggers for Regression	Exclusions
New onset poor sleep	Transitions	Autism spectrum disorder presents in 5 years and above
Change in language output	(e.g., changes in an individual’s home/school/college routine)	Medical causes (incl. thyroid dysfunction and other conditions with autoimmune aetiology)
Abulia, withdrawal, disinterest, personality changes	Life events	New onset sensory impairment
Mood changes, loss of appetite and weight loss	Stressors	Age-related decrease in activity
Motor features–catatonia, stereotypies, extra-pyramidal signs		Other mental illness (e.g., depression)
Loss of skills (adaptive functioning)		Unlikely over the age of 40 years (dementia is possible)