While hormones have long been associated with powerful changes in mood, internal state, and behavior, recent work has begun to deepen our understanding of how these changes occur at both the mechanistic and computational levels. Sex hormones, which include estrogens, progesterone, and androgens, are present in varying amounts in both males and females, and circulating levels can change as a result of development, endogenous cycling, or behavior itself (McEwen and Milner, 2017, Gurvich et al., 2018, Jennings and de Lecea, 2020). Recent work focused on understanding the computational properties of sex hormones has frequently focused on females. This is apt, considering that hormonal transitions throughout a woman's lifespan are closely linked to changes in emotional states as seen in mood and anxiety changes during premenstrual, postpartum, and perimenopausal stages (Barth et al., 2023, Kundakovic and Rocks, 2022). Women face twice the risk of developing persistent negative emotional states, including anxiety and depression compared to men, with cycling sex hormones identified as a key biological factor contributing to this disparity (Cover et al., 2014, Eliot et al., 2023). Hormone withdrawal has also been shown to induce depressive symptoms and negative emotional states including reduced sociability in mice (Tao et al., 2023).

Exogenous alteration of hormonal profiles is also widespread. Millions of people globally use oral contraceptives (Lacasse et al., 2024), and menopausal women as well as gender-diverse individuals rely on hormone therapies (Aghi et al., 2022, Camon et al., 2024). Breast cancer survivors also rely on anti hormonal therapies, such as estrogen receptor degraders or aromatase inhibitors, to prevent recurrence (Ingraham et al., 2022). Many of these compounds cross the blood–brain barrier, impacting hormone-sensitive brain regions. Estrogens can also act as antidepressants or enhance the efficacy of existing treatments (Dossat et al., 2018). The effects on mood and emotional state are complex and influenced by several factors (Schuh et al., 2024) such as hormone formulation, dosage, schedule, and the individual's psychiatric history. Understanding the impact of these exogenous hormones on brain and emotional states is crucial for creating tailored formulations, empowering informed decision-making, improving gender-affirming care, and enhancing mental health for a significant portion of the population.