Biological risks occurring during the prenatal and neonatal periods have been frequently associated with adult psychopathology. However, environmental influences are rarely examined along the same pathway, and outcomes in areas of psychosocial wellbeing have received little attention. It is important to examine environmental mechanisms in the association between biological risks and adult psychopathology, and to extend this pathway to psychosocial wellbeing, to identify potentially modifiable processes and whether the same mechanisms are implicated in both areas of adult psychological development.

This thesis examined the role of one environmental mechanism – childhood trauma – in the association between biological risks (prenatal stress, neurodevelopmental adversity) and adult psychopathology (depression, psychosis) as well as psychosocial wellbeing (self-concept). Four studies were designed: the first two investigated the effect of prenatal stress and neurodevelopmental adversity on depression and psychotic experiences in adulthood in the general population, and the role of caregiver- and peer-inflicted trauma. The last two studies used longitudinal data from the preterm population, which acted as a proxy measure indicating multiple exposures to neurodevelopmental adversity, and examined outcomes in psychotic experiences and self-concept in relation to peer-inflicted trauma (i.e peer bullying).

Findings from these studies consistently showed a mediating effect of childhood trauma, in particular peer bullying, even after accounting for important confounders and genetic risks. Despite biological risks having a small effect on the outcomes examined, a significant proportion was mediated via childhood trauma. A dose-response effect was also observed: increased exposure to childhood trauma was associated with increased risk for depression, psychotic experiences, and decreasing self-concept.

These findings suggest the importance in adopting a developmental cascade approach, where early biological risks may lead to increasing difficulties in childhood which cumulates in psychopathology or adverse wellbeing. Resources should focus on identifying high-risk groups who are more likely to be exposed to childhood trauma, as well as interventions to reduce childhood trauma in the general population. These findings further highlight the importance of routinely assessing childhood trauma and adopting a trauma-informed approach in clinical settings.