Why do mood swings occur before a period?

Reviewed by Yoshinori Abe, MD

Internal Medicine

Mood swings before a period are a common symptom of premenstrual syndrome (PMS), often caused by hormonal fluctuations that influence brain chemicals like serotonin, which regulates mood. In the days leading up to menstruation, shifts in estrogen and progesterone can trigger irritability, sadness, anxiety, or emotional sensitivity. While these mood changes are typically normal, severe or disruptive symptoms may indicate a condition like premenstrual dysphoric disorder (PMDD).

If your mood swings feel overwhelming or interfere with daily life, it's worth understanding the root cause. Take a free, instant, online symptom check to explore what may be behind your symptoms and get personalized guidance on what to do next.

Reviewed for medical accuracy: 07/20/2026

Important Next Steps

Learn why period mood swings happen Discover if your mood swings need care See what could cause your symptoms Find OTC relief for period mood swings Find a doctor for period-related symptoms Explore home remedies for mood swings Understand if mood swings signal PMS

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Explanation

Mood swings before a period, often called premenstrual syndrome (PMS), can be linked to hormonal changes in the body. Hormones like estrogen and progesterone fluctuate during the menstrual cycle, and these changes can affect mood and emotions. Some women experience mood instability, which means their emotions can change quickly or feel more intense.

Research shows that women with PMS experience more mood swings than those without it. These mood changes can include feelings of sadness, irritability, or anxiety. Not all women experience mood swings before their period, and the severity can vary.

If mood swings are severe or cause significant distress, it may be helpful to talk to a healthcare provider. To better understand your symptoms and get personalized guidance, try our free AI symptom checker.

(References)

Bowen R, Bowen A, Baetz M, Wagner J, & Pierson R. (2011). Mood instability in women with premenstrual syndrome. Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstetrique et gynecologie du Canada : JOGC, 21923990.
Metcalf MG, Livesey JH, Wells JE, & Braiden V. (1989). Mood cyclicity in women with an without the premenstrual .... Journal of psychosomatic research, 2795513.
Farage MA, Osborn TW, & MacLean AB. (2008). Cognitive, sensory, and emotional changes associated .... Archives of gynecology and obstetrics, 18592262.

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