Reaching underrepresented groups in mental health research: Sex differences and reproductive events in bipolar disorder

Yang, Jessica ORCID: https://orcid.org/0000-0002-3685-4126 2026. Reaching underrepresented groups in mental health research: Sex differences and reproductive events in bipolar disorder. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

This thesis aimed to explore the genetic and phenotypic heterogeneity of bipolar disorder, with a specific focus on sex differences and reproductive events, namely childbirth. The first step was to examine sex differences in bipolar disorder using the largest available datasets of bipolar disorder to date (N=89,592). I first aimed to compare the genetic architecture of bipolar disorder in male and female participants separately (Chapter 2) and identified several sex-dependent genetic effects. Second, I tested for sex differences in the lifetime symptoms of bipolar disorder (Chapter 3) and found that sex differences were dependent on bipolar disorder diagnostic subtype and the presence of cases of postpartum psychosis. Removing cases of postpartum psychosis, whilst only making up a small proportion of the dataset, significantly impacted results. Considering the important role of postpartum psychosis in the previous chapter, Chapiter 4 details the first genome-wide association study and genetic correlation analysis of postpartum psychosis. This analysis provided evidence for postpartum psychosis as a more heritable and less pleiotropic condition compared to bipolar disorder in female participants; however, it was limited by small sample size and a lack of diversity. My final results chapter therefore focused on the feasibility of international studies of postpartum psychosis (Chapter 5). I ran focus groups in collaboration with researchers in India and Malawi with women with lived experience, their families and healthcare professionals. It emerged that the term “postpartum psychosis” and experience of the condition itself remain consistent across cultures and contexts, despite differences in service provision, access and pathways to care. Together, these results demonstrate the benefits of stratifying bipolar disorder by sex and experience of postpartum psychosis, thus improving characterisation of bipolar disorder, which, in turn, may facilitate research by providing more homogenous groups to identify biological mechanisms, risk factors and causes.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Schools > Medicine
Date of First Compliant Deposit:	17 August 2026
Last Modified:	17 Aug 2026 16:42
URI:	https://orca.cardiff.ac.uk/id/eprint/189015

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