Genetic influences on structural and functional brain maturation

Understanding typical brain development in children and adolescents is important because it provides a baseline for what is to be considered aberrant development. This knowledge can also be used to determine what parts of the brain is responsible for cognitive and behavioral development in adolescence and can inform on psychiatric disorders that have their onset in adolescence, such as schizophrenia. With a longitudinal twin study design, the genetic and environmental influences on brain and behavior, as well as their developmental changes, can be disentangled.

In this thesis, I show that i) the thickness of the cerebral cortex and its rate of development during adolescence is largely under genetic control, with a new genetic factor marking the transition during adolescence; ii) functional connectivity in the adolescent brain is in part also determined by genes, along with several indications of influences from common environment, that remain largely stable over time. This suggests that the development of the structure of the brain is considerably influenced by genes, while the functioning of the brain is more flexible to adapt to the environment. Patients with schizophrenia experience accelerated aging. I looked at accelerated aging based on the structure of the brain and epigenetic modifications, and found iii) no clear evidence that these two aging processes are related despite that both are partially determined by genes implicated in schizophrenia. This suggests the possibility for two distinct aging processes affecting accelerated aging in patients with schizophrenia.