A prospective case series of high-risk infants who developed autism.

Doctors watched a small group of high-risk babies from 6 to 24 months. All of the infants later got an autism diagnosis.

The team tracked IQ, social cues, sensory quirks, and fussiness every few months. They wrote detailed stories about each child’s path.

Two clear roads showed up. One group lost IQ points and showed autism signs early. The other group kept average IQ and looked typical longer.

Fussy crying, poor eye contact, and odd arm or mouth movements were the first red flags in both roads.

Peristeri et al. (2024) followed similar kids for four more years. They saw the same split: some IQs dropped, others rose. Their longer view proves the split is real and lasts.

Ben-Itzchak et al. (2021) used a parent checklist called the First Year Inventory on hundreds of babies. It caught about one in three future autism cases by 12 months. Their big sample shows the early signs E et al. saw in a few babies hold up in the real world.

Houwen et al. (2014) looked at older autistic youth and found lower IQ after age eight. Their data line up with the infant decline road E et al. first drew, showing the slide can keep going.

You can spot the at-risk road before the official diagnosis. Watch 6- to 12-month-olds who rarely share smiles, hate being held, flap hands, or stay cranky despite soothing. Track quick IQ screens and sensory quirks at each visit. When both show up together, start early teaching and parent coaching right away instead of waiting.