PMS: Why It Happens and What Actually Helps

Premenstrual syndrome is among the most common and most routinely dismissed conditions there is: roughly three quarters of women of reproductive age report some premenstrual symptoms. The range is enormous — from mild discomfort to a state that removes several days a month from a person's life. Here is what happens physiologically and which measures have real evidence behind them.

What happens in the body#

The popular "hormonal imbalance" explanation is wrong. Studies show that oestrogen and progesterone levels are essentially identical in women with and without significant PMS. The difference lies in the central nervous system's response to normal cyclical fluctuation.

The prime suspect is allopregnanolone, a progesterone metabolite acting on GABA-A receptors much as benzodiazepines do. In most women it is calming, but in some the response is paradoxical, producing irritability and anxiety. A second mechanism involves the serotonin system: sex hormone fluctuations affect serotonergic transmission, which explains why SSRIs work quickly for PMDD and at lower doses than for depression.

Additional contributions come from fluid retention driven by changes in the renin-angiotensin-aldosterone system and from increased pain sensitivity during the luteal phase.

Symptom cluster	Manifestations
Affective	Irritability, anxiety, low mood, tearfulness, abrupt mood shifts
Cognitive	Difficulty concentrating, forgetfulness, a sense of brain fog
Physical	Breast tenderness, bloating, swelling, headache, joint and muscle pain
Behavioural	Cravings for sweet and salty food, appetite changes, disturbed sleep, reduced motivation

Telling PMS apart from other conditions#

The key diagnostic criterion is timing. In PMS, symptoms appear in the luteal phase (usually 5–11 days before menstruation) and disappear within the first days after it begins, leaving at least a week symptom-free.

If symptoms persist throughout the cycle and merely intensify beforehand, that is not PMS but premenstrual exacerbation of an existing condition — depression, an anxiety disorder, migraine, irritable bowel syndrome, endometriosis. The approach then differs: the underlying condition is what needs treating.

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What helps: the evidence hierarchy#

Measure	Evidence	How to apply
Regular aerobic exercise	Moderate to strong	150 minutes a week; helps both mood and physical symptoms
Calcium 1000–1200 mg/day	Moderate	From food and supplements; reduces affective and physical symptoms
Reducing alcohol	Moderate	Especially in the luteal phase — it worsens irritability and sleep
Less salt and caffeine	Low to moderate	Salt for swelling, caffeine for anxiety and breast tenderness
Adequate sleep	Moderate	Sleep loss amplifies emotional reactivity
Vitamin B6 up to 100 mg/day	Moderate	Higher doses risk peripheral neuropathy
Chasteberry (Vitex)	Low to moderate	Several RCTs for breast tenderness and mood
Magnesium	Low	Evidence inconsistent
Evening primrose oil	Low	Reviews do not confirm an effect
Cognitive behavioural therapy	Moderate	Effective for affective symptoms

A word on food specifically. Craving sweet things in the luteal phase is physiological: energy expenditure rises slightly, and serotonin fluctuations increase the pull towards fast carbohydrates. Fighting it with prohibitions is usually counterproductive. What works instead: raising the protein and fibre content of meals to smooth glycaemic swings, and avoiding long gaps between meals.

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Medication options#

If non-drug measures fall short and symptoms disrupt life, medication is discussed. A clinician makes that decision.

• SSRIs. Per the Cochrane review, effective in PMS and PMDD, and they work quickly — often within the first cycle. Intermittent dosing is possible: taking them only during the luteal phase, reducing overall exposure. It is one of the few psychiatric indications where that approach is justified.
• Combined oral contraceptives. They suppress ovulation and the fluctuations tied to it. The best-studied regimens use drospirenone with a shortened hormone-free interval. They do not suit everyone: contraindications include migraine with aura and thromboembolic risk.
• NSAIDs. For headache, muscle and joint pain, and period pain.
• Spironolactone. Sometimes used for pronounced swelling and breast tenderness, on prescription.

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What doesn't work#

• "Cleansing" and detox regimens — no effect on the cycle.
• Cutting carbohydrates entirely — worsens irritability and intensifies cravings.
• Severe fluid restriction for swelling — luteal-phase swelling reflects hormonal sodium regulation, not how much you drank; limiting salt is the sensible target.
• Progesterone supplements for ordinary PMS — reviews do not support effectiveness.
• Ignoring symptoms. The belief that "everyone has this" delays help by years, especially in PMDD.

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The bottom line#

PMS arises not from "bad hormones" but from heightened brain sensitivity to their normal fluctuations. The diagnosis rests on symptoms tracking the luteal phase and clearing once menstruation begins — which is exactly why a two-cycle diary is so valuable. Among non-drug measures, the best-supported are regular physical activity, 1000–1200 mg of calcium a day, less alcohol, salt and caffeine, and adequate sleep. For severe forms, effective treatment exists — SSRIs and hormonal contraceptives — and there is no reason to endure it.