For many years, autism has been identified as a spectrum with differing levels of ability. New research suggests that the age when symptoms first appear may help anticipate the specific traits, behaviors and genetic markers associated with an individual’s specific type of autism.

“Unraveling the complexity of autism is a particularly challenging yet critical task for supporting the needs of autistic individuals and understanding the biology, inheritance, trajectory and phenotypes of the many forms of the condition,” the authors of a July study in Nature Genetics wrote.

Autism affects fewer than one in 100 individuals and presents as a diverse group of conditions centering around degrees of difficulty with social and interpersonal interactions and communication as well as unusual patterns of activities and repetitive behaviors, according to the World Health Organization.

People with autism may have difficulty transitioning from one activity to another, focus intently on small details or have unusual reactions to sensory stimulus. The abilities and needs of autistic individuals vary greatly and can evolve over time.

The paper’s authors looked at individual traits, presentations and genetic markers to power an analysis of 5,000 autistic children identified in a database managed by the nonprofit Simons Foundation, which supports science research. Their work revealed four sets of observable characteristics that correspond to a clear set of genetic markers for each group.

The social/behavioral group met early developmental milestones on time, with other conditions posing challenges later in development, including attention defecit / hyperactivity disorder and depression. They tended to be diagnosed later, at 6 to 8 years, and accounted for 37% of participants.

The moderate challenges group showed milder social and communication differences and repetitive habits, and no significant delays in skills like walking or communication. This group included one third of the participants.

The mixed autism spectrum disorder with developmental delays group included almost 20% of participants, who showed early delays in key milestones but few signs of anxiety, depression or disruptive behavior. Members varied in how strongly individual social and repetitive behaviors presented.

The broadly affected group was smallest — one in 10 participants — but displayed more challenging traits, including persistent developmental delays, strained communication and social interaction, and more pervasive repetitive behaviors.

An October article in the journal Nature affirmed some of the researchers’ conclusions, matching different ages of diagnosis with specific life trajectories.

“These findings provide further support for the hypothesis that the umbrella term ‘autism’ describes multiple phenomena with differing … developmental trajectories and correlations with mental-health conditions,” that study’s authors wrote. “Our findings have important implications for how we conceptualize autism and provide a model to explain some of the diversity found in autism.”

— Karl Hille / The Baltimore Sun

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