The relationship between personality trait change and major life events is currently undergoing extensive investigations within the field of personality psychology. A debate has risen regarding whether or not major life events can bring about trait change, and how typical trait change patterns over the adult lifespan can be explained. It is valuable to understand how traits change because they predict important future outcomes. The Five-Factor Theory described by McCrae and Costa (2008a) states that traits are purely biological entities, and trait change is explained to result from processes of intrinsic biological maturation, unaffected by life events. This thesis reviewed the literature regarding the relationship of trait change and life events, and the research of potential biological bases of traits in the brain together with a brain developmental perspective of intrinsic maturation. Gaining an insight in the relationship between personality traits and the brain is a goal within a young field of research called personality neuroscience, and an agenda of the Five-Factor Theory. Major life events do cause trait change, but the relationship is complex. A brain developmental perspective of intrinsic maturation did not entirely correspond with patterns of typical trait change in young adulthood. The Five-Factor Theory is challenged and modifications are suggested. Neurobiological correlates of five-factor traits reveal issues and potentials for future research.