PhD defence B. (Bing) Xu

Below is a brief summary of the dissertation:

Mental health problems that begin in childhood and adolescence can strongly influence how people develop throughout their lives. Understanding the biological mechanisms behind early psychiatric symptoms is therefore important for improving diagnosis, treatment, and prevention. Brain imaging has great potential to support this, but translating research findings into clinical practice remains difficult. One major challenge is that psychiatric symptoms in youth often overlap across different disorders and change over time depending on developmental stages, individual variability, and environmental influences. This thesis addresses these challenges in two main parts. The first part investigates how brain development, genetics, and psychiatric symptoms relate to each other during childhood and adolescence. Using large population-based cohorts, the Generation R Study in the Netherlands and the Adolescent Brain Cognitive Development (ABCD) Study in the US, this work analyzes data from nearly 17,000 children. The findings show that genetic susceptibility to psychiatric disorders is linked to divergent neurodevelopmental trajectories and differences in brain structure. For example, higher genetic susceptibility to schizophrenia was associated with altered development of frontal brain regions. The second part focuses on identifying generalizable brain-behavior associations that could predict psychiatric symptoms. Using machine-learning methods, the research identified patterns in brain structure that were consistently associated with attention problems across independent populations. Overall, the results highlight both the promise and the challenges of using neuroimaging to understand and predict psychiatric problems in youth. Large datasets, rigorous validation, and integrating genetics, neuroimaging, and behavioral data will be essential for developing clinically useful biomarkers in the future.