Football behind bars: psychosocial mechanisms of wellbeing and social integration in a prison-based sport programme.

Fluctuations in oestrogen and progesterone play a vital role in women’s health from menarche to menopause, and the brain is an active endocrine organ in this complex hormonal interplay. These powerful sex hormones orchestrate a cascade of neurobiological changes spanning multiple scales—from microscopic remodelling of the epigenome, cellular architecture and nanoscale refinement of synaptic connectivity at dendritic spines to macroscopic alterations in brain volume and network connectivity patterns. Hormone-dependent neuroplastic adaptations occur in brain regions rich in oestrogen and progesterone receptors, including the hippocampus, amygdala and prefrontal cortex, where they modulate cognitive function, emotional processing and stress responses throughout the reproductive lifespan. Importantly, these hormonal fluctuations constitute essential signalling mechanisms that maintain neural homeostasis and confer cognitive flexibility. Understanding these complex neuroendocrine interactions provides crucial insights into neurological and psychiatric conditions which have a higher prevalence in women or a unique aetiology in the female brain. The cellular basis for the effects of oestrogen and progesterone on the brain has been extensively studied in the rodent hippocampus, where hormone cycling drives remarkable structural plasticity and impacts memory. Several ground-breaking studies performed by McEwen and Woolley in the 1990s found that when oestrogen circulation was highest during the proestrus phase of the rodent oestrous cycle, the connectivity and signalling of hippocampal circuits were elevated, as evidenced by increased dendritic spine density, synaptogenesis and excitatory signalling. During the oestrus phase (after ovulation), when oestrogen is lowest, such features were retracted, and hippocampal astrocytic process extension increased, marking this more pro-inflammatory phase. While fluctuations in oestrogen orchestrate these microstructural changes, the rise of progesterone during late proestrus and slow decline during oestrus were found to coordinate the precise rhythmic timing of the changes such that they were complete by late oestrus. Non-invasive neuroimaging has been a useful tool for identifying changes to regional brain structure with respect to fluctuations in sex steroids in both rodents and humans, where comparison of brain structure and function during the late-follicular and late-luteal phases provides a suitable analogue to the high versus low oestrogen phases in rodents. One distinct exception to the conservation of this hormonal cycle is that oestrogen peaks during ovulation in humans and rats do not undergo menses (). Several studies have demonstrated that grey matter volume is highest during the late-follicular/poestrus phase and lowest during the early follicular/oestrus phase, with the greatest changes occurring in the hippocampus. In parallel to the cellular findings, it has been suggested that the temporal progression of oestrogen-mediated volumetric changes is also progesterone-dependent. However, not all regions follow this trend, indicating that region specificity is imperative for understanding the effects of oestrogen and progesterone on brain structure. In an exploratory longitudinal study where one female subject was repeatedly scanned using diffusion-weighted imaging across two menstrual cycles, it was found that hippocampal fractional anisotropy, an analogue measurement of tissue organization related to the restriction of water molecule movement within tissue, was highest during ovulation, suggesting that the hippocampus may be particularly organized when oestrogen is highest. These volumetric and microstructural alterations have functional consequences, as evidenced by shifts in cognitive strategies employed during different cycle phases. During high oestrogen phases, subjects (human and rodent) predominantly use hippocampal-based strategies for spatial navigation, while during low-oestrogen phases, striatal-based strategies dominate. With the rapid advancement of techniques to assess nuanced changes in brain structure and function over time with respect to circulating hormones, neuroimaging is becoming a promising tool for assessing women’s brain health.