ADHD Prevalence in Turner Syndrome
Approximately 24-26% of patients with Turner syndrome meet diagnostic criteria for ADHD, representing an 18-fold increase compared to girls in the general population.
Evidence-Based Prevalence Data
The most rigorous study examining ADHD prevalence in Turner syndrome found that 24% of girls with Turner syndrome met strict DSM-IV criteria for ADHD, compared to only 1.3% of girls in the general population (p < 0.01) 1. This represents a clinically significant 18-fold increase in ADHD prevalence 1.
More recent data from multidisciplinary clinic assessments confirm this finding, with 26% of Turner syndrome patients receiving formal ADHD diagnoses on comprehensive neuropsychological testing 2. An Egyptian tertiary center study reported a similar prevalence of 20.7% for ADHD in their Turner syndrome cohort 3.
Clinical Context and Comorbidity Patterns
Girls with Turner syndrome who have autism spectrum disorder (ASD) are at particularly high risk for co-occurring ADHD 4. In one comprehensive assessment of 127 girls with Turner syndrome, 23% met diagnostic criteria for ASD, and those with ASD had substantially elevated rates of comorbid ADHD 4.
The neurodevelopmental profile in Turner syndrome is characterized by:
- Lower performance IQ relative to verbal IQ, which may contribute to attention difficulties 2, 3
- Executive function impairments, particularly in integrative tasks 5
- Social communication difficulties in 83% of patients, which can overlap with or exacerbate ADHD symptoms 4
Karyotype Considerations
While some evidence suggests that 45,X karyotype may be associated with lower full-scale IQ compared to mosaic karyotypes (p = 0.027), the prevalence of ADHD does not appear to differ significantly by karyotype 2. Importantly, no imprinting effects from the parental origin of the intact X chromosome have been demonstrated for either cognitive performance or ADHD prevalence 1.
Clinical Implications for Screening
Routine neuropsychological screening for ADHD should be performed at key developmental transitions in all patients with Turner syndrome, given the 24-26% prevalence rate 2. This screening is particularly critical because:
- ADHD symptoms may be overshadowed by other Turner syndrome features 4
- Early detection allows for appropriate behavioral management from preschool through adolescence 4
- Comorbid conditions (anxiety in 26%, specific learning disorders in 18%) frequently co-occur and require integrated management 2
The median age for formal neuropsychological assessment in specialized clinics is 11.3 years, though earlier screening may be warranted given the developmental trajectory of ADHD symptoms 2.