Exploring violence, poor mental health and harmful substance use among FSWs in Nairobi and their association with hair cortisol levels

BACKGROUND AND AIM: Female sex workers (FSWs) in sub-Saharan Africa face increased risks of adverse life events such as violence, poor mental health, and harmful substance use, which are linked to increased vulnerability to HIV. However, the connection between these exposures and HIV acquisition may not be fully explained by behavioural risk factors alone. Stressful life events can impair the hypothalamic-pituitary-adrenal (HPA) axis, influencing cortisol production, which plays a crucial role in health, including immune function. Dysregulated cortisol levels are associated with higher T-cell activation (e.g., CD8+), which may increase susceptibility to HIV infection. The aim of my PhD is to explore stressors, specifically violence, poor mental health and harmful substance use, among FSWs in Nairobi and examine the relationship between cortisol levels and these exposures. METHODS: My PhD is a longitudinal mixed-methods study using data from the Maisha Fiti study of 1,003 FSWs in Nairobi, Kenya. For the qualitative component, participants shared their life stories through semi-structured interviews, discussing their entry into sex work, experiences of violence, mental health, and substance use. I thematically analysed 40 baseline interview transcripts in Nvivo to explore their lifetime mental health experiences and perceived risks. Quantitative data were collected via a behavioural-biological survey at baseline and follow-up. Participants reported recent violence, poor mental health, and harmful substance use, while hair samples were collected to measure cortisol via Enzyme-linked immunoabsorbent Assay (ELISA) technique. I used linear regression to assess associations between these categories of exposures and hair cortisol levels at baseline and longitudinal data to analyse changes in cortisol over time in relation to the trajectories of violence, mental health, and substance use. My thesis consists of three manuscripts: a qualitative study on FSWs’ experiences of mental health and other psychological stressors in their lives (Paper 1) and two quantitative studies investigating the association between hair cortisol with violence, mental health, and substance use cross-sectionally at baseline (Paper 2) and longitudinally using data at baseline and endline (Paper 3). FINDINGS: Qualitative analysis revealed that 28 out of 40 participants reported poor mental health, driven by poverty, limited education, inadequate job opportunities, lack of family support, harmful gender norms, intimate partner violence, relationship breakdowns, and family bereavement. Sex work further exacerbated their mental health due to sexual risks and ongoing violence from police and clients. Quantitatively, baseline data from 425 HIV-negative participants showed a high prevalence of recent violence (89.3%), including physical (54.6%), sexual (49.4%), emotional (77.0%), and financial (66.5%) violence. Mental health issues were prevalent, with 23.7% reporting moderate/severe depression, 11.6% moderate/severe anxiety, 13.5% post-traumatic stress disorder (PTSD), and 10.8% recent suicidal thoughts. Harmful alcohol or other substance use was reported by 48.8%. Physical and/or sexual violence and harmful alcohol and/or other substance use were independently associated with increased hair cortisol concentrations at baseline (HCC). Longitudinally, HCC levels decreased significantly from baseline to endline, with change in HCC levels at endline linked to trajectories of physical violence as well as physical and/or sexual violence. CONCLUSION: FSWs in Nairobi face significant mental health challenges, driven not only by the high-risk sex work environment but also by structural factors like intimate partner violence, poverty, and relationship breakdowns before entering sex work. Quantitative findings suggest that physical/sexual violence and harmful substance use may disrupt the HPA axis, potentially linking these exposures to increased HIV infection risk among FSWs. Findings in this PhD highlight the urgent need for targeted interventions addressing stressors such as violence, poor mental health and harmful substance use among FSWs in Nairobi. There is also a critical need for support interventions for women and girls experiencing distressful events to prevent poor mental health and subsequent entry into sex work.