PMS vs PMDD: how premenstrual syndrome and premenstrual dysphoric disorder differ

Premenstrual syndrome (PMS) is the name for symptoms that can occur in the weeks before a period. The NHS says each person's symptoms are different, can vary from month to month, and that most women have PMS at some point. Premenstrual dysphoric disorder (PMDD) is the severe form. The NHS describes its symptoms as similar to PMS but much more intense, with a much greater negative impact on everyday life.

So the two are best thought of as points on a spectrum rather than two unrelated conditions. Many people have mild premenstrual changes that need no treatment at all. PMS sits in the middle, where symptoms are distressing enough to want help. PMDD is at the far end, where the mood symptoms in particular can take over the second half of the cycle.

CKS makes an important point about where the line falls. It notes that physiological premenstrual symptoms are experienced by up to 90% of women, so to call something PMS, it must be shown that the symptoms cause significant impairment during the luteal phase. In other words, having premenstrual symptoms is common; having symptoms that disrupt your life is what makes it a condition worth treating.

The table below pulls together what the NHS and CKS say about the two. It is a guide to the general picture and not a diagnostic tool, because the decision rests on a clinician looking at a symptom diary and your history.

It is the overlap that makes the two hard to separate at home. The NHS lists the usual PMS symptoms as mood swings, feeling depressed or irritable, feeling upset, anxious or emotional, tiredness or trouble sleeping, bloating or cramping, breast tenderness, headaches, spotty skin, greasy hair, and changes in appetite or food cravings. PMDD draws on the same pool, so a person can recognise almost every item on the PMS list in their PMDD.

Cause is another shared uncertainty. The NHS says it is not fully understood why women get PMS, but it may be because of changes in hormone levels during the menstrual cycle, with some women more affected than others. For PMDD it says the cause is unclear, and that it has been linked to being very sensitive to changes in hormones, or to certain differences in inherited genes.

The behavioural and psychological symptoms also matter in both. CKS groups them as psychological (depression, anxiety, irritability, loss of confidence and mood swings), physical (bloating and breast pain) and behavioural (reduced cognitive ability and aggression). Treating the picture as "just hormones" can underplay how disruptive that can be.

There is no blood test that confirms either condition. CKS describes the approach: a detailed history, a physical examination as indicated by age and routine gynaecological recommendations, and a daily symptom diary kept for two or three cycles.

The diary is what turns a vague sense of "I am worse before my period" into evidence. CKS says the diagnosis of PMS should be confirmed if the diary shows symptoms prominent in the luteal phase that resolve with the onset of menstruation or soon after, followed by a symptom-free week; if the symptoms are severe enough to affect work, school, performance or relationships; and if other conditions that could explain the symptoms are absent. CKS gives depression, hypothyroidism, anaemia, irritable bowel syndrome and endometriosis as examples to consider.

Once PMS is established, the question of PMDD is mostly one of counting and weighing. The DSM-5 threshold quoted by CKS is five of 11 symptoms with at least one related to mood, and clear distress or impairment. A clinician looks at how many symptoms appear in the diary, whether a mood symptom is among them, and how much functioning is affected. The International Association for Premenstrual Disorders, a patient-led charity, also describes premenstrual exacerbation (PME) alongside PMDD, which is a reminder that an existing condition can sometimes be the real driver and that a clinician needs to consider it.

For PMS, the NHS suggests regular exercise, a healthy balanced diet (some find smaller meals every 2 to 3 hours better), plenty of sleep, stress reduction through yoga or meditation, painkillers such as ibuprofen or paracetamol for pain, and not smoking or drinking too much alcohol. It says to see a GP if lifestyle changes have not helped or the symptoms are affecting daily life.

CKS says management should be tailored to severity, impact and type of symptoms, the woman's preferences and any plans to become pregnant. Everyone with PMS should be offered lifestyle advice, an NSAID for pain if suitable and patient information. Additional options include a drospirenone-containing combined oral contraceptive pill (off-label if contraception is not needed), cognitive behavioural therapy, and a selective serotonin reuptake inhibitor (off-label), particularly where symptoms are severe or mood symptoms dominate. A review after 2 months is suggested, and referral to a clinic with an interest in PMS if primary care cannot control symptoms.

The NHS adds that complementary therapies and supplements such as vitamin B6, calcium, vitamin D and magnesium may help but that there is not much evidence they work, and that anyone taking other medicines should check with a GP or pharmacist first. If symptoms persist after treatment, referral may be to a gynaecologist, psychiatrist or counsellor.

Make a GP appointment if premenstrual symptoms are interfering with work, study, relationships or your sense of yourself, or if lifestyle changes have not been enough. A written diary of at least two cycles, with the days of your period marked and each symptom scored, makes the conversation quicker and more productive.

Treat suicidal thoughts as urgent whatever the time of the month. The NHS says to call 999 or go to A&E if you have PMDD symptoms and are feeling suicidal, and not to drive yourself: ask someone to take you or call an ambulance. If feelings like this appear every cycle, tell a clinician as soon as you can, because it points firmly towards the severe end of the spectrum and deserves a treatment plan.