Genetic and environmental influences on structural brain measures in twins with autism spectrum disorder

Abstract

Atypical growth patterns of the brain have been previously reported in autism spectrum disorder (ASD) but these alterations are heterogeneous across individuals, which may be associated with the variable effects of genetic and environmental influences on brain development. Monozygotic (MZ) and dizygotic (DZ) twin pairs with and without ASD (aged 6–15 years) were recruited to participate in this study. T1-weighted MRIs (n = 164) were processed with FreeSurfer to evaluate structural brain measures. Intra-class correlations were examined within twin pairs and compared across diagnostic groups. ACE modeling was also completed. Structural brain measures, including cerebral and cerebellar gray matter (GM) and white matter (WM) volume, surface area, and cortical thickness, were primarily influenced by genetic factors in TD twins; however, mean curvature appeared to be primarily influenced by environmental factors. Similarly, genetic factors accounted for the majority of variation in brain size in twins with ASD, potentially to a larger extent regarding curvature and subcortical GM; however, there were also more environmental contributions in twins with ASD on some structural brain measures, such that cortical thickness and cerebellar WM volume were primarily influenced by environmental factors. These findings indicate potential neurobiological outcomes of the genetic and environmental risk factors that have been previously associated with ASD and, although preliminary, may help account for some of the previously outlined neurobiological heterogeneity across affected individuals. This is especially relevant regarding the role of genetic and environmental factors in the development of ASD, in which certain brain structures may be more sensitive to specific influences.

On the Nature of Monozygotic Twin Concordance and Discordance for Autistic Trait Severity: A Quantitative Analysis

“…Recently, Hegarty et al ( 2019 ) observed greater environmental influences on some aspects of brain morphometry (cortical thickness and cerebellar white matter volume) in twins with ASD than in normal twins; however, most of the observed effects were attributable to shared rather than non-shared environment. The latter dominated our observations and could encompass epigenetic changes, random developmental (in utero) or environmental (extrauterine) perturbations, or the effects of somatic mutations, to which affected individuals might be more vulnerable than unaffected individuals.…”

Understanding the genetic contribution of the human leukocyte antigen system to common major psychiatric disorders in a world pandemic context

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Gestational age and the risk of autism spectrum disorder in Sweden, Finland, and Norway: A cohort study

“…ASD is more than three times more common in males than in females [6]. Even though a specific etiology can be identified in some individuals with ASD, most of the variation in ASD risk is believed to have its origin in a complex interaction between genetic and environmental factors [7][8][9]. The occurrence of ASD has increased over the past three decades, partly reflecting changes in diagnostic criteria and increased awareness [5].…”