Autism isn’t one condition but four, according to new research that could help children get diagnosed earlier and receive more tailored support.
Scientists in the US analysed data from more than 5,000 children and found the disorder falls into four clear types, each with its own set of traits, risks and causes.
The findings could help explain why some are diagnosed late, why some develop other mental health problems, and why the condition can look very different from one person to the next, they say.
The most common, seen in 37 per cent of cases, was marked by difficulties with socialising and repetitive behaviours—but no delays in early development.
Children in this group are often diagnosed later and are more likely to develop conditions such as ADHD, anxiety or depression.
Researchers found this type was linked to genes involved in later brain development, which may explain the delayed diagnosis.
The second group, called ‘Moderate Challenges’, made up 34 per cent of cases and showed similar behaviours but without the raised risk of mental health problems.
The third group, described as ‘Mixed ASD with Developmental Delay’, made up around one in five children with the condition.
Scientists have discovered there are four different and distinct types of autism in a step they have called a ‘paradigm shift’ for future treatment of the disorder. Stock image
These children reached key milestones—such as walking and talking—later than expected, and showed a combination of social and behavioural traits typical of autism.
They were not more likely to develop mental health conditions.
The final and least common type, ‘Broadly Affected’, accounted for just 10 per cent of cases.
Children in this group showed the most severe symptoms, including profound developmental delays and a high risk of additional psychiatric conditions.
They also had the highest number of damaging de novo mutations—genetic changes that occur spontaneously in the womb rather than being inherited.
Professor Olga Troyanskaya, senior author of the study and a specialist in genomic data at Princeton University, said: ‘Understanding the genetics of autism is essential for revealing the biological mechanisms that contribute to the condition, enabling earlier and more accurate diagnosis, and guiding personalised care.’
Psychologist Jennifer Foss-Feig, another author of the study, added that knowing a child’s autism subtype could help parents spot key signs of mental health conditions or developmental issues.
‘It could tell families, when their children with autism are still young, something more about what symptoms they might—or might not—experience, what to look out for over the course of a lifespan, which treatments to pursue, and how to plan for their future,’ she said.
This chart shows the percentage increase in incidence of autism diagnosis from 1998 to 2018. UK researchers found autism diagnoses had risen by an ‘exponential’ 787% over 20 years. They said the rise could be due to increased recognition of the condition among experts particularly in diagnosing autism among girls and adults, but added an increase in cases of autism itself cannot be ruled out
The findings, published in Nature Genetics, are based on an analysis of 233 individual traits linked to autism, including language development, cognitive ability, social behaviour and mental health symptoms.
The researchers used this data to group children into four types, then examined their genetic information to look for patterns.
The authors emphasised that the four types of autism is just a foundation, and there may be more or sub-types within each group, adding this was an area of further research.
Their discovery comes amid rising concern autism may be over diagnosed in England, with an eight-fold increase in cases in recent decades.
British researchers have said worrying rise is likely due to increased awareness of the condition but have added an increase in prevalence could also be contributing.
An additional factor experts say could be influencing the rise is the retirement of Asperger’s syndrome.
This was once considered a separate condition but is now considered another form of autism.
However, others have pointed to the ‘wild-west’ of autism screening in England that could mean over-diagnosis could also be playing a part.
Last year a study revealed adults referred to some autism assessment facilities have an 85 per cent chance of being told they are on the spectrum.
Yet the figure can be as low as 35 per cent in other places, researchers at University College London found.