Polycystic ovary syndrome (PCOS) is among the most common endocrine disorder in women of reproductive age, and is associated with several burdensome comorbidities. Around half of women with PCOS are either unaware of their condition or only become diagnosed a considerable time after symptoms initially manifest. PCOS presents significant challenges for both healthcare professionals and the women affected by the condition. Due to its multifaceted nature, there is currently no straightforward treatment available, and this has been the status quo for decades. Further investigation is needed to understand the etiology of PCOS and how PCOS contributes to socioeconomic and health inequalities. 

This PhD thesis aims to generate new knowledge on intergenerational and early life drivers of PCOS, while contributing to a better understanding of the mechanisms that generate social inequalities in PCOS. The four individual studies are based on register data for large population samples of Swedish women born between 1962 and 1995. 

Study I investigated associations of intergenerational and early life factors with PCOS. Maternal PCOS diagnosis, maternal diabetes mellitus, maternal obesity and heavy maternal smoking (10+ cigarettes/day) were strongly associated with PCOS among offspring. Additionally, lower (<7) one-minute Apgar score and post-term birth were associated with diagnosis of PCOS.

Study II investigated associations between PCOS and several comorbidities, exploring the extent to which these associations are sensitive to familial confounding by exploiting variation between biological sisters. After controlling for some shared familial environmental, social, and genetic risk factors, the findings indicated that women with a PCOS diagnosis had a fourfold increase in the odds of being diagnosed with obesity, a 1.4-fold higher likelihood of experiencing depression or anxiety, and a twofold greater likelihood of developing sleep, sexual, or eating disorders compared to their sisters without PCOS.

Study III focused on labor market attachment trajectories of working age women diagnosed with PCOS. While the majority of women in the study sample entered the labor market with stable employment, those with PCOS were more likely to encounter negative labor market outcomes, such as exclusion from the labor market or prolonged sickness absence. 

Study IV aimed to quantify educational and income-related inequalities and their relation to PCOS diagnosis. Women with low socioeconomic position had highest risk for being diagnosed with PCOS even after controlling for confounding factors. A modifying effect of education on the association of income with PCOS was also observed. 

The findings of this thesis highlight the impact of intergenerational factors and early life conditions on the risk of developing PCOS later in life. In addition to its developmental origins, PCOS leads to disadvantaged labor market attachment trajectories later in life. The thesis also explores the link between a disadvantaged socioeconomic situation and PCOS.

The complexity of working with register data and diagnosed cases of PCOS lies in chronological delays and underdiagnosis. Women whose PCOS diagnosis is not captured by the registries or is only observed later than the onset of the disease may bias estimates obtained from register studies, which is a limitation. Screening for PCOS, particularly among women with risk factors such as obesity, or a family history of the condition, could help identify the disorder earlier. Early detection allows for timely interventions and could also reduce the risk of associated comorbidities such as obesity, type 2 diabetes, cardiovascular disease, and mental health disorders. Integrated care models are needed that address the full spectrum of PCOS-related health and social issues.