Study questions link between rising diagnoses of autism, ADHD and actual symptoms in teens

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Rates of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) diagnoses have risen sharply in recent decades, particularly among teenagers and young adults. However, a new Swedish twin study suggests that this surge in diagnoses may not reflect a corresponding increase in underlying symptoms.

Researchers from the Gillberg Neuropsychiatry Centre at the University of Gothenburg, Karolinska Institutet, and other institutions analysed data from 9870 twins born between 1993 and 2001, as part of the Child and Adolescent Twin Study in Sweden (CATSS). Parents reported on their children’s ASD and ADHD symptoms when the twins turned 18.

The findings, published in Psychiatry Research, indicate no overall rise in autism-related symptoms across the nine birth years studied. For ADHD, the picture was more nuanced: boys showed stable levels, while girls exhibited a small but statistically significant increase in parent-reported symptoms. At the most severe levels (top 10 percent of scores), ADHD symptoms rose only among girls.

Lead author Olof Arvidsson, a physician and PhD student, and colleagues suggest that the rapid increase in ASD and ADHD diagnoses among adolescents and young adults is unlikely to stem from a genuine surge in symptoms. Instead, they point to other contributing factors, including:

• Broader diagnostic criteria that encompass more individuals.
• Increased public and professional awareness leading to higher referral and assessment rates.
• A shift in how symptoms are perceived, with certain behaviours now considered more impairing amid rising stress and academic demands among Swedish teenagers.

In short, today’s youth are not necessarily experiencing more symptoms of autism or ADHD. Rather, similar behaviours may be recognised and diagnosed more frequently than in the past.

For parents, the main message is this: autism and ADHD are real and significant conditions, but the growing number of diagnoses largely reflects changes in awareness and diagnostic practices, not an actual epidemic of symptoms. The researchers emphasise the need for careful use of diagnostic categories to ensure that support reaches the young people who truly need it.

Text written by Anna Spyrou, Communications Officer