遺伝学：自閉スペクトラム症の遺伝的に異なる形態

The age that autism is diagnosed may partly reflect underlying biological and developmental differences among individuals with autism, finds a study published in Nature. The research identifies distinct developmental and genetic patterns between those diagnosed in early childhood and those diagnosed later, typically from late childhood onwards, with implications for understanding co-occurring mental health conditions.

Autism is an umbrella term that covers many differences within the neurodevelopmental condition, but clear ways to distinguish these differences remain limited. Although social and demographic factors have been linked to age at diagnosis, the role of genetics has not been well studied. As more people are getting diagnosed later in life, often alongside conditions such as anxiety, attention deficit–hyperactivity disorder (ADHD) and depression, understanding these differences is increasingly important.

Using behavioural data from 4 birth cohorts, ranging from 89 to 188 individuals, and genetic data from two large studies, Varun Warrier and colleagues found that common genetic variants explain around 11% of the variation in age at autism diagnosis. They identified two groups with different behavioural trajectories with separate genetic profiles: one where social and communication difficulties, such as anxiety, hyperactivity and difficulties with social interaction, appear early but remain stable, and another where such difficulties increase during adolescence. Those, on average, diagnosed from late childhood onwards were also more likely to experience mental health conditions such as depression compared with those who received a diagnosis earlier in childhood. The authors found that the genetic differences between these different groups were comparable to those between psychiatric conditions, rather than within one.

The findings suggest that autism diagnosed at different ages may reflect distinct developmental pathways and provides a clearer way to understand variation within the diverse condition. The findings may help guide future research and support strategies. The authors conclude that further research on diverse genetic ancestries is needed.