The clinical presentation of ADHD in adults with Learning Disability: experience from a National Specialist Adult ADHD clinic

Background

There is growing evidence that ADHD is more common in children and adults with Learning Disabilities (LD) and that it can be successfully treated even if diagnosis can be difficult because of ‘diagnostic overshadowing’. This study provides empirical data about the ADHD symptoms in LD and non-LD populations.

Materials and methods

The sample consisted of 48 LD-ADHD (IQ< 80) adults compared to 221 ADHD non -LD (IQ>=80) adults. Symptoms were evaluated using the informant-rated Barkley scale for childhood and adulthood behaviour. T-tests, paired samples t-tests and principal component analysis were conducted to investigate the pattern of symptoms for each group.

Results

The LD group differed significantly from the non LD group for a number of the current inattentive symptoms' ratings and presented also higher scores for all items during childhood, indicating greater severity of symptoms. For the non-LD group, most symptoms improved from childhood to adulthood. However, for the LD group, there was overall improvement as indicated by the total score, but no items showed significant change from childhood to adulthood.

Principal component analysis for current symptoms in the LD revealed scattered loading of different items into five components to account for 73.98% of the variance for informants' ratings. These components were not consistent with the classic cluster of inattentive, hyperactive and impulsive symptoms as was the case for the non-LD group.

Conclusions

ADHD symptoms can be identified successfully in LD patients, however clinicians should be aware that the pattern of the clinical presentation can be different for this clinical population.