Despite the increasing media coverage concerning the impacts of the menopause on women’s mental health, this remains an under-researched area. Menopause affects quality of life, work, and relationships and is also a period of increased risk of depression. Depressive symptoms during menopause are often attributed to hormonal changes, but life stressors that coincide with the menopausal transition could also have a depressogenic effect. Earlier research, based mainly on cross-sectional data, has found that a later age at menopause and a longer reproductive period are associated with a lower risk of depression. This may reflect a greater lifetime exposure to oestrogen, which is thought to have an antidepressant effect in women. Limitations of previous studies include inadequate adjustment for confounders; lack of control for premenopausal depression, and failure to account for other factors affecting lifetime oestrogen exposure (e.g. oral contraceptives, breastfeeding, number of pregnancies) or hormone replacement therapy. Very few studies have sought to uncover the biopsychosocial mechanisms that might explain increased levels of depression during the menopausal transition. This project aims to advance understanding of women’s mental health during menopause by applying cutting edge causal inference methods.