Trends in autism research 2021

Sex differences

Because autism is most often diagnosed in boys, researchers have a history of ignoring girls with the condition. But that bias is changing, as evidenced by an increasing number of studies on sex differences in autism.

Traits such as aggression and communication problems are related in autistic boys but not autistic girls, one study from 2021 showed. Another found that autistic women and girls pay more attention to faces than autistic men and boys do — which, along with the fact that autistic girls have an increased likelihood of having a co-occurring condition, may explain some of the diagnostic bias.

Researchers are grappling with what causes these differences, but autistic girls tend to have larger genetic mutations than autistic boys do — leading to sex differences in brain activity, according to one 2021 study, and lending support to the idea of a ‘female protective effect.’ Another 2021 analysis found that the X chromosome holds an outsized influence over brain development, which could serve to establish sex differences early on. Given these differences, researchers caution against using brain activity as an autism biomarker. Autistic men and women show different patterns of resting-state brain activity, for example, one 2021 analysis revealed.

Scroll through the study highlights below.

The ‘dark genome’

In the search for autism-linked mutations, researchers have focused mainly on genes — which make up only 2 percent of the genome. This year, however, autism scientists made inroads exploring vast stretches of DNA that don’t code for proteins. One sequencing study implicated what may be the first three spontaneous mutations in noncoding regions tied to the condition. Such mutations contribute to autism in at least 2 percent of people on the spectrum, according to another 2021 study. And noncoding mutations play a role in the ‘second hit’ theory of autism genetics, an analysis from November shows, amplifying the effects of mutations in the autism-linked chromosomal region 16p12.1.

Noncoding mutations may also shape when and where autism-linked genes are most active during brain development, which a new atlas of gene expression in the fetal brain maps out for mid-gestation. And mutations in enhancers — noncoding regions that boost gene expression — occur far more often in people with autism than in those without, according to an analysis of postmortem brain tissue from this past January.

Improving screening

Researchers deployed several new strategies this year to try to upgrade autism screening and, in many cases, render the process remote — although questions remain about some app-based systems. A new deep-learning model flags autistic toddlers based on the patterns of other conditions noted in the children’s medical records. A mobile app that tracks toddlers’ gaze patterns accurately distinguishes those with autism from their non-autistic peers. And a web app for tracking pupillary responses — which can be slower in people with autism — proved reliable as well this year. Wearable devices could also help clinicians detect early signs of the condition, new works shows.

Other teams are seeking to optimize existing screening practices. This past year, one group uncovered a long-standing error in the guidelines for one popular autism screening test. Another team boosted autism screening rates at pediatric clinics in Utah by, among other changes, adding reminders to electronic health records. And a growing number of researchers is pushing to expand genetic screening for newborns to improve early identification of some autism-linked conditions.

Scroll through the study highlights below.