Newswise — A long-term study by researchers at the UC Davis MIND Institute confirms that changes in IQ levels in children with autism may help predict pathways of adolescent communication and behavioral development .
The new study builds on previous MIND Institute research on IQ trajectories in children with autism aged 2 to 8. It extends the findings to older adolescents.
This study, published in JCPP Advances, identifies three distinct pathways of intellectual development in children with autism. It is permanent intellectual disability, increased IQ, or above average IQ.
Lead author Marjorie Solomon said, “We have once again shown that IQ can be used to identify subtypes of autism. She is Associate Director and Professor of Psychiatry and Behavioral Sciences at the MIND Institute. “Given that IQ is the strongest predictor of subsequent outcomes in children with autism, we believe it is of great importance to study the trajectory of IQ during childhood. It provides clues about a wide variety of future avenues and how we can help individuals thrive.”
Participants in this study were participants in the MIND Institute’s Autism Phenomena Project, one of the world’s most comprehensive longitudinal studies of its kind. Researchers have followed a group of children with autism from around the age of three until adolescence.
The study included 373 individuals with autism (115 females and 258 males) aged 2 to 12 years.
Assessments of behavioral and autistic traits were collected throughout childhood. IQ was assessed at his three time points: T1 (mean age 3 years), T2 (mean age 5.6 years) and T3 (mean age 11.5 years).
A licensed clinical psychologist who specializes in autism assessed participants using the Autism Assessment Tool. These include ADOS (Autism Diagnostic Observation Schedule), ADOS-2, ADI-R (Autism Diagnostic Interview – Revision), and Vineland Adaptive Behavior Scale (VABS).
Based on these assessments, participants were divided into three subgroups:
- “Changers” describe people who started out with low IQs in childhood and then slowed their IQ gains significantly as they entered middle school. “Changer” made up his 39% of participants.
- “Persistent intellectual disability” describes an individual who began with a below-average IQ that persisted throughout childhood. About 45% of the participants belonged to this group.
- “Sustainably high IQ” describes individuals who started with average or above average IQ and remained relatively stable throughout childhood.16% belonged to this group.
The researchers analyzed the characteristics of autism and changes in communication adaptive function. This is the ability to understand a language over time, make meaningful verbal expressions, and read and write.
They also looked at internalizing behaviors such as anxiety and depression and externalizing behaviors such as impulsivity and aggression.
Of the 191 participants evaluated at two or more time points, 10 lost their autism diagnosis. This included approximately 5% of the ‘Changers’, 10% of the ‘Permanently high IQ’ group, and none of the ‘Permanent intellectual disability’ group. Identifying what distinguishes the ‘changers’ group from those with more stable IQs is the main goal of the study.
Individuals with strong early communicative adaptations and low autism ‘severity’ scores were more likely to belong to the ‘permanently high IQ’ group by puberty versus the ‘permanent intellectual disability’ group. I got taller.
Both the ‘changers’ and ‘persistent intellectual disability’ groups had low IQ scores in early childhood. However, those with improved communication adaptation function and decreased externalizing behavior during adolescence were more likely to belong to the ‘changer’ group than the ‘persistent intellectual disability’ group.
“It’s surprising that we found so much overlap in individuals following different trajectories of intellectual development when assessed at early childhood and adolescent time points,” Solomon said. , while many other factors are involved in determining outcome, intellectual ability level is a core characteristic and an important starting point.”
Brain Differences Between Three Autism Groups
Last year, a closely related MIND Institute study compared MRI scans of three IQ subgroups at age three. Researchers evaluated two brain networks in his brain associated with intellectual function.
The frontoparietal network is involved in sustained attention, problem solving, and working memory. The network in default mode remembers, thinks about the future, wanders.
The 2022 study was led by Joshua Lee, a research fellow in the Department of Psychiatry and Behavioral Sciences. The team found that the ‘Changers’ and ‘Intellectually Impaired’ groups, who had lower IQs at age 3, differed from those with average IQs in several areas of the frontoparietal network.
In contrast, the “Changers” group and the other two groups had different networks in default mode. This difference suggests that this network may be involved in mechanisms related to improved intellectual function.
“The results of both studies provide clues as to how differences in the brains of autistic and non-autistic children with and without intellectual disability in early childhood predict future outcomes.” , said Christine Wu Nordahl, director of the Autism Phenomena Project, professor in the Department of Psychiatry and Behavior. Science and co-author of both studies. “Future studies will assess the development of brain structure and function during childhood and how they differ among different subgroups of intellectual development in autism.”
Additional co-authors of the new study include UC Davis’ Billy Cho, Ana-Maria Iosif, Brianna Heath, Apurv Srivastav, Emilio Ferrer and David G. Amaral.
This study was funded by the National Institute of Mental Health (R01MH106518, R01MH103284, R01MH103371, R01MH104438). National Institutes of Health (R01MH104438); T32 Ruth L. Kirchstein Institutional National Research Service Award (T32 MH073124). MIND Institute Center for Intellectual and Developmental Disabilities Research (P50 HD103526); Autism Center of Excellence Grant (P50 HD093079) from the National Institute of Child Health and Development.
Read the full study.