Table 1 Biological, clinical, and family history variables included in the analysis, which eventually identified the four subgroups used in the study (from Sacco et al. 2010)

Age at non-verbal language development

History of allergies

Pregnancy duration

Age at verbal language development

History of regression

History of obstetric complications or recurrent spontaneous abortions in the mother

Level of verbal language development

History of obstetric complications at or immediately after birth

History of any allergic and/or immune disease in the family

Age at walking

History of any infectious disease at autism onset

History of tumors in the family

Age at acquisition of bladder control at night

History of sleep disorders

History of any neurological or psychiatric disorders in the family

Age at first social smile

Presence of muscle hypotonia at neurological examination

Motor, verbal or vocal stereotypies

EEG pattern (evaluated at T0)

Self-aggressive or self-injurious behaviour

Pain sensitivity (reported by parents)

Hyperactivity