When anxiety or depression seems to come on suddenly, many people try to link it to a stressful week at work or a major life event. Far fewer realize that hormones can directly drive those shifts. When estrogen, progesterone, thyroid hormones, or testosterone rise and fall during puberty, pregnancy, perimenopause, menopause, or endocrine disorders, the brain’s systems for regulating stress, sleep, and emotion can be pushed off balance. Recognizing how these hormonal changes