Tests of intelligence adjust for age, so intelligence quotients are generally expected to remain stable throughout a person’s lifetime. But the participants’ IQs increased with age even as their autism traits remained stable, the researchers found.
The 35 participants whose parents reported a regression in language skills early in childhood showed the largest increase in IQ, gaining about 13 IQ points on average, compared with about 7 in the whole group. The work appeared in December in the Journal of the American Academy of Child & Adolescent Psychiatry.
“The most plausible explanation to me is that children who regress are those whose otherwise underlying trajectory was one of normal-high development in terms of cognition,” she says. “Then something happened to perturb this trajectory — and also to cause autism.” Then throughout adolescence, she says, these participants gradually returned to their earlier developmental trajectory.
In this way, she says, early regression may mark a unique autism trajectory, distinct from those of children with slower but steadier cognitive development.