An investigation into the relationship between dimensions of infant temperament and lifespan psychological development.

In this proposal, I outline an innovative multidisciplinary PhD project investigating the role of infant temperament in influencing lifespan development at the behavioural, genetic and cognitive level. Existing research has explored these relationships, but adequately powered longitudinal studies that extend to adulthood are lacking. This research is needed to further the understanding of the developmental processes involved in the emergence of mental health traits, which can inform early interventions.

Infant temperament includes dimensions such as surgency, behavioural inhibition and attachment disorganisation. It can be understood broadly as individual differences in behavioural and emotional reactivity observed at a very young age. These temperamental traits are moderately stable over time and are influenced strongly by genetic and environmental factors (Papageorgiou & Ronald, 2017; Rettew & McKee, 2005; Tang et al., 2020). Early temperament has also been shown to be related to dimensions of personality in adulthood (Caspi et al., 2003) and certain dimensions have been linked to childhood psychopathology (Sayal, Heron, Maughan, Rowe, & Ramchandani, 2014). Evidence relating to the connection between infant temperament and later psychopathology is largely limited to outcomes in childhood and adolescence, however, with little research concerning outcomes in adulthood, focusing on lifespan development.

One notable exception to this is a longitudinal cohort study by Tang et al. (2020) which demonstrated that the relationship between infant temperament and psychopathology can extend beyond adolescence into adulthood. The authors found that behavioural inhibition in infants younger than 1 year old can predict the later development of internalising psychopathologies (anxiety and depression) at 26 years of age. Although this research had limitations, such as a small and heterogeneous sample (n=109 at 26-year follow-up), it provides a proof-of-concept for the proposed research, which will investigate the same longitudinal trajectory but with larger samples and a broader scope of mental health trait outcomes, e.g. psychotic experiences, Attention Deficit Hyperactivity Disorder (ADHD), and Autism Spectrum Disorder (ASD).