An Examination of Prenatal, Neonatal and Childhood Risk Factors for Psychiatric Symptoms and Disorders.

Background: It is becoming increasingly evident that experiences throughout one’s life impact mental wellbeing. Understanding the aetiology of psychiatric disorders through the identification of early life risk factors for psychiatric disorders is essential for both intervention and prevention.Aims: This thesis aimed to investigate four potential early life risk factors for adverse psychiatric outcomes, specifically, prenatal stress, maternal tobacco smoking during pregnancy, birth weight and childhood temperament, as well as investigating possible associations between these four risk factors.Methods: For studies one, two, three, four and six, I ran a series of varying regression models, using two longitudinal cohorts, examining associations between the four previously mentioned risk factors and adverse psychiatric outcomes, including clinical diagnosis of a psychiatric disorder and persistent psychiatric symptoms. In addition, for study four, I also ran a mediation analysis testing possible pathways between prenatal smoke exposure, birth weight, and psychiatric symptoms. Finally for study five, I systematically reviewed the literature examining associations between childhood temperament, its constituent factors and subsequent depression or anxiety.Results: Studies one and two found that prenatal stress exposure was associated with increased odds of developing both any psychiatric disorder, and specific psychiatric disorders including depression and personality disorder. Study three showed associations between prenatal stress and prenatal smoking, and between prenatal smoking and the development of any psychiatric disorder and specifically personality disorder. Study four replicated associations between prenatal smoke exposure and psychiatric symptoms, while also finding associations between birth weight and psychiatric symptoms. Additionally, study four also found that birth weight mediated the relationship between prenatal smoking and psychiatric symptoms. Study five systematically reviewed the literature showing associations between childhood temperament, its constituent factors, and depression or anxiety and found consistent associations between emotionality/affectivity, and effortful control with depression/anxiety; sociability/shyness/inhibition and anxiety; reactivity and mixed depression and anxiety symptoms. Finally, study six showed associations between difficult childhood temperaments, reduced positive mood, reduced adaptability, and reduced approach-withdrawal with increased odds of developing psychotic disorder. Study six also found associations between reduced regularity and increased threshold with increased odds for depressive disorder.Conclusion: The results of this thesis emphasize the importance of early life factors in the development of adverse mental health outcomes. These studies provide evidence regarding on the aetiology of psychiatric disorders, and can potentially inform the development of new preventative interventions and the implementation of evidence-based healthcare policies.