60 and 80 percent heritable<\/a>, it\u2019s hard to pin down a specific genetic cause for any one individual\u2014the cause is only clear for about 20 percent of autistic people tested, Litman explains. Researchers have now identified hundreds of genes associated with autism, meaning that if an individual has certain genes, they have a much higher chance of being diagnosed as autistic. But even with this knowledge, scientists haven\u2019t been able to reliably connect how these genes translate to specific autistic traits and developmental trajectories.<\/p>\nTo bridge that gap, Litman, Sauerwald and their colleagues turned to data from a large study that tracked genetic information, traits and development of 5,392 autistic kids between the ages of four and 18. The researchers evaluated the young participants on social communication abilities, restrictive and repetitive behaviors, developmental milestones, and more. Using a computer model, statistical tests and clinical judgment, the team separated the participants into four robust groups based on patterns in their traits and development.<\/p>\n
Social and Behavioral Challenges: These kids, 37 percent of the participants, had more difficulty with social communication and restrictive and repetitive behaviors than other autistic children. They also had more challenges with disruptive behavior, attention and anxiety. These children, however, did not experience significant developmental delays.<\/p>\n
Mixed ASD with Developmental Delay: These kids, 19 percent of the participants, were more varied in their social communication and restrictive and repetitive behaviors, and they showed some developmental delays compared with nonautistic children.<\/p>\n
Moderate Challenges: These kids, 34 percent of the participants, had consistently fewer difficulties with social communication, restrictive and repetitive behaviors and other core autistic traits compared with other autistic children\u2014though they still had more difficulties with them than nonautistic children. They did not have developmental delays.<\/p>\n
Broadly Affected: These kids, 10 percent of the participants, had more severe and wide-ranging difficulties with social communication, restrictive and repetitive behaviors and other core autistic traits, including developmental delays, compared with other autistic children.<\/p>\n
These groups still contained a lot of variation within them, but participants in each were more similar to one another than they were to participants in other groups. The four groups were also replicated in another, smaller population of autistic children.<\/p>\n
The researchers then analyzed genetic differences across the four groups and found that, remarkably, they had very distinct genetic profiles. \u201cTo me, the biggest surprise was how different the four subtypes turned out to be…. The underlying genetics and biology are very different,\u201d says Olga Troyanskaya, a genomics researcher at Princeton and the study\u2019s senior author. For example, different genes become active at different times in development\u2014some become relevant before birth; others do so after. The Social and Behavioral Challenges group had more mutations in genes that became active after birth, Litman and Troyanskaya say, which could explain why these participants did not have developmental delays and tended to be diagnosed later than those in the other three groups.<\/p>\n
\u201cI expected these subtypes to have some differences in their biological underpinnings,\u201d says Sauerwald, but the differences were even more pronounced than she expected, with very little biological overlap.<\/p>\n
These four groups aren\u2019t entirely unfamiliar to Volkmar and Lord, neither of whom were involved in the study. \u201cThe groups make sense and follow lots of findings by other researchers,\u201d Lord says. In that regard, the subtypes \u201chave a \u2018rediscovering the wheel\u2019 aspect,\u201d Volkmar says\u2014it\u2019s the connection to genetics that makes these results most noteworthy.<\/p>\n
These subgroups almost certainly don\u2019t cover the entire autism spectrum, given that the results were based on a sample that didn\u2019t represent the autistic population at large. The sample was 77 percent white, and some portions of the genetics results could only be performed for people with European ancestry because of limitations in available data. Also, some traits related to autism are rare and may not have been present enough in the sample to be picked up by the researchers\u2019 statistical measurements. \u201cThis classification is not a definitive, comprehensive grouping,\u201d Troyanskaya says. \u201cWith additional data, more precise definitions of subtypes could emerge.\u201d<\/p>\n
For Volkmar, the study \u201cspeaks to the need to be a bit more fine-grained in our approaches to diagnosis,\u201d he says. \u201cIt spurs us to think about new approaches\u201d to how to diagnose and understand autism\u2014with subtypes rather than a single condition.<\/p>\n","protected":false},"excerpt":{"rendered":"Researchers Identify Four Autism Subtypes with Distinct Genes and Traits Autism has at least four subtypes, an analysis…\n","protected":false},"author":2,"featured_media":48516,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[64,63,336,128],"class_list":["post-48515","post","type-post","status-publish","format-standard","has-post-thumbnail","category-genetics","tag-au","tag-australia","tag-genetics","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/48515","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=48515"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/48515\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/48516"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=48515"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=48515"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=48515"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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