Neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) have revealed structural deviations of the corpus callosum in children and adolescents. However, little is known about the link between callosal morphology and symptoms of inattention or hyperactivity in adulthood, especially later in life.

We aimed to further expand this understudied field by analyzing a large population-based sample of 280 adults (150 males, 130 females) in their late sixties and early seventies.

We applied a well-validated approach capturing the thickness of the corpus callosum with a high regional specificity at 100 equidistant points. In addition to correlating point-wise callosal thickness with ADHD symptom measures within the whole sample, we tested for sex interactions.

There were significant sex interactions with respect to measures of inattention and hyperactivity, with follow-up analyses revealing significant negative correlations in males (see Fig. 1 – Top). In contrast, there were positive correlations with respect to hyperactivity only in females (see Fig. 1 – Bottom).

A thinner corpus callosum may be associated with fewer fibers or less myelination. Thus, the negative correlations, as observed in males, suggest an impaired inter-hemispheric communication necessary to sustain motor control and attention, which may contribute to symptoms of hyperactivity, impulsivity and/or inattention. The functional relevance and underlying mechanisms of the positive correlations, as detected in females, remain to be resolved.