Thesis defense Winke Francx (Donders series 240)

22 September 2016

Promotors: Prof. dr. J. Buitelaar, Prof. dr. C. Beckmann, copromotors: Dr. M. Mennes en Dr. M. Zwiers

On neural networks related to ADHD as a continuous disorder

Attention Deficit/Hyperactivity Disorder (ADHD) is one of the most common childhood psychiatric disorders, affecting about 5% of all school age children worldwide. Adult ADHD has a population prevalence of 2-3%. At this time, it remains unclear why some children show remission while others continue to present with full or partial symptoms of ADHD in adulthood. The studies in this thesis are aimed at investigating whether and how the developmental course of ADHD is reflected in brain correlates.

The first part of this thesis describes how developmental changes in ADHD symptoms relate to connectivity patterns in white and grey matter. Following the investigation of cross-sectional MRI data, the sample was tracked over a longer period of time and a second MRI scan was collected. Data now covered a period of approximately 10 years. In the last part of this thesis, a more complex analysis method is used to integrate MRI data of distinct modalities. This technique opens possibilities for neurobiological subtyping of ADHD using multimodal data. Subtyping is an important topic in ADHD literature as the disorder is marked by large heterogeneity. In this thesis more traditional categorical group comparisons are combined with dimensional analyses. The latter allow the more precise tracking of individual changes over time and prevent the use of an arbitrary diagnostic threshold.

In conclusion, this thesis is contributing to unraveling the mechanisms behind developmental trajectories of ADHD. On the long-term this might lead to the possibility of prediction of developmental trajectories and more effective treatments adapted to individual developmental trajectories.