Temperament and character as endophenotype in adults with autism spectrum disorders or attention deficit/hyperactivity disorder.
Temperament surveys give only weak evidence that adult ADHD is a mild form of autism.
01Research in Context
What this study did
Researchers asked if adult ADHD is simply a mild form of autism. They gave temperament and character surveys to adults with autism, adults with ADHD, and adults with neither diagnosis.
The team compared seven personality scales across the three groups. They looked for patterns that would support a continuum between the two conditions.
What they found
Only two out of seven scales showed the smooth gradient predicted by the continuum idea. The other five scales did not line up in a neat autism-to-ADHD sequence.
In plain words, the data only partly supports the view that ADHD is autism-lite. Most temperament differences did not fall on one straight line.
How this fits with other research
Ganz et al. (2009) studied teens with high-functioning autism and found low surgency and high negative mood predicted poorer daily skills. That study looked at autism alone, while the current paper compares autism directly with ADHD in adults.
Amorim et al. (2025) worked with youth who had autism, ADHD, or OCD. They saw that IQ and social communication scores mattered more than the diagnostic label itself. Both papers weaken the idea that diagnoses sit on one clear ladder.
Bhaumik et al. (2008) showed cognitive traits like Theory of Mind form a continuum across typical and autistic youth. The current study moves the question into adult temperament and finds only partial overlap, suggesting cognitive and personality domains may behave differently.
Why it matters
When you assess an adult who might have autism or ADHD, do not assume one is a softer version of the other. Check each domain separately—social communication, attention, impulsivity, and emotional traits. Tailor goals to the pattern you see, not to the label alone.
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02At a glance
03Original abstract
Autism spectrum disorder and attention deficit/hyperactivity disorder overlap in several ways, raising questions about the nature of this comorbidity. Rommelse et al. published an innovative review of candidate endophenotypes for autism spectrum disorder and attention deficit/hyperactivity disorder in cognitive and brain domains. They found that all the endophenotypic impairments that were reviewed in attention deficit/hyperactivity disorder were also present in autism spectrum disorder, suggesting a continuity model with attention deficit/hyperactivity disorder as "a light form of autism spectrum disorder." Using existing data, 75 adults with autism spectrum disorder and 53 with attention deficit/hyperactivity disorder were directly compared on autistic symptoms with the autism spectrum quotient, and on the endophenotypic measure of temperament and character, using the Abbreviated (Dutch: Verkorte) Temperament and Character Inventory. Based on the hypothesis that attention deficit/hyperactivity disorder and autism spectrum disorder are disorders on a continuous spectrum, autism spectrum quotient scores and abbreviated Temperament and Character Inventory scores were expected to be different from normal controls in both disorders in a similar direction. In addition, the autism spectrum quotient and abbreviated Temperament and Character Inventory scores were expected to be closely correlated. These conditions applied to only two of the seven Abbreviated Temperament and Character Inventory scales (harm avoidance and self-directedness), suggesting that temperament and character as an endophenotype of autism spectrum disorder and attention deficit/hyperactivity disorder provides only partial support for the continuity hypothesis of autism spectrum disorder and attention deficit/hyperactivity disorder.
Autism : the international journal of research and practice, 2015 · doi:10.1177/1362361314522352