Abstract

OBJECTIVE: White matter alterations are frequently reported in autism spectrum disorder (ASD), yet the etiology is currently unknown. The objective of this investigation was to examine, for the first time, the impact of genetic and environmental factors on white matter microstructure in twins with ASD compared to control twins without ASD.METHOD: Diffusion-weighted MRIs were obtained from same-sex twin pairs (aged 6-15 years) in which at least one twin was diagnosed with ASD or neither twin exhibited a history of neurological or psychiatric disorders. Fractional anisotropy (FA) and mean diffusivity (MD) were examined across different white matter tracts in the brain and statistical and twin modeling were completed to assess the proportion of variation associated with additive genetic (A) and common/shared (C) or unique (E) environmental factors. We also developed a new version of the twin-pair difference score analysis method that estimates the contribution of genetic and environmental factors to shared covariance between different brain and behavioral traits.RESULTS: Good quality data were available from 84 twin pairs, 50 ASD pairs [32 concordant for ASD (16 monozygotic; 16 dizygotic), 16 discordant for ASD (3 monozygotic; 13 dizygotic), and 2 pairs in which one twin had ASD and the other exhibited some subthreshold symptoms (1 monozygotic; 1 dizygotic)] and 34 control pairs (20 monozygotic; 14 dizygotic). Average FA and MD across the brain, respectively, were primarily genetically mediated in both control twins (A=0.80 [0.57,1.02]; A=0.80 [0.55,1.04]) and twins concordant for having ASD (A=0.71 [0.33,1.09]; A= 0.84 [0.32,1.36]). However, there were also significant tract-specific differences between groups. For instance, genetic effects on commissural fibers were primarily associated with differences in general cognitive abilities and perhaps some diagnostic differences for ASD, e.g., our new twin-pair difference-scores analysis indicated that genetic factors may have contributed to 40-50% of the covariation between IQ scores and FA of the corpus callosum. Conversely, the increased impact of environmental factors on some projection and association fibers were primarily associated with differences in symptom severity in twins with ASD, e.g., twin-pair difference-scores suggested that unique environmental factors may have contributed to 10-20% of the covariation between autism-related symptom severity and FA of the cerebellar peduncles and external capsule.CONCLUSION: White matter alterations in youth with ASD are associated with both genetic contributions and potentially increased vulnerability or responsivity to environmental influences.DIVERSITY & INCLUSION STATEMENT: We worked to ensure sex and gender balance in the recruitment of human participants. We worked to ensure race, ethnic, and/or other types of diversity in the recruitment of human participants. We worked to ensure that the study questionnaires were prepared in an inclusive way. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented racial and/or ethnic groups in science. One or more of the authors of this paper self-identifies as a member of one or more historically underrepresented sexual and/or gender groups in science. One or more of the authors of this paper self-identifies as living with a disability. The author list of this paper includes contributors from the location and/or community where the research was conducted who participated in the data collection, design, analysis, and/or interpretation of the work.

View details for DOI 10.1016/j.jaac.2023.05.030

View details for PubMedID 37406770