Purpose <p>This review examines why women experience insomnia at higher rates than men, addressing how biological, psychophysiological, and sociocultural mechanisms interact to increase vulnerability and informs gender-specific treatments.</p> Methods <p>A literature search of PubMed, PsycINFO, and Scopus (2000–2024) identified studies examining sex or gender differences in insomnia. Findings were synthesized across biological, psychophysiological, and sociocultural domains, with attention to treatment implications.</p> Results <p>The vulnerability of women to insomnia is multifactorial. Biologically, sleep is influenced by hormonal fluctuations that occur during the menstrual cycle, pregnancy, and menopause. Genetic studies have shown higher heritability in women (~ 59%) than in men (~ 38%), with certain risk genes (e.g., <i>MEIS1</i>) exerting stronger effects in women. Neuroimaging findings link female insomnia to alterations in emotion regulation regions (e.g., limbic circuitry), whereas male insomnia is more associated with sensory-processing networks. Psychophysiologically, women exhibit greater cognitive-emotional arousal, including rumination, and heightened stress-related sleep reactivity than men. Socioculturally, these vulnerabilities are amplified by gendered stressors, particularly work–family conflict, while men’s insomnia is more closely related to occupational strain. Pharmacologically, sex-informed treatment targets orexin-mediated hyperarousal, GABAergic signaling, and hypothalamus–pituitary–adrenal axis activity. Non-pharmacologically, women-specific care extends cognitive behavioral therapy for insomnia to address rumination, emotional regulation, and work–family stress within a gender-sensitive framework.</p> Conclusion <p>Insomnia in women is best conceptualized as a diathesis–stress condition. Mechanism-based gender-informed interventions are needed to optimize clinical outcomes.</p>