Cortisol and hair loss: can stress make your hair fall out?

Stress can make your hair fall out, but usually only for a while, and not in the simple way it is often described. A stressful event, an illness, childbirth or rapid weight loss can push more hair follicles than usual into their resting phase, and a few months later those hairs shed. Cortisol, the body's main stress hormone, is one of the signals thought to be involved: hair follicles respond to stress hormones and even make their own. But most of that evidence comes from laboratory and animal studies, and in people the exact part cortisol plays in hair loss is still unclear. This guide sets out what is known, and what a hair cortisol test can and cannot tell you if your hair is thinning.

Can stress make your hair fall out?

Yes, for a time. Losing 50 to 100 hairs a day is normal, and the NHS lists illness, stress, weight loss and iron deficiency among the causes of temporary hair loss. Male and female pattern baldness, which usually runs in families, is the common permanent type.¹

The form of hair loss most closely tied to stress is called telogen effluvium. Each hair follicle cycles between growing and resting. At any one time about 85 per cent of scalp follicles are growing hair and about 15 per cent are resting before the hair sheds. In telogen effluvium, the resting share rises to 30 per cent or more.² Recognised triggers include childbirth, severe illness (especially with a high fever), major injury or surgery, stressful life events, marked weight loss or extreme dieting, starting certain medicines and stopping hormonal treatment such as the contraceptive pill. In about 1 in 3 people no cause is found.²

The timing often confuses people. Shedding usually starts suddenly about three months after the trigger, lasts about three to six months, and is followed by regrowth, although restoring full thickness can take many months. It usually settles without treatment, and it typically causes thinning all over the scalp rather than bald patches. Shedding that continues for more than six months is called chronic telogen effluvium.² So hair loss you notice now may reflect something that happened a season ago.

Hair loss is also stressful in its own right. Researchers have noted that telogen effluvium and pattern hair loss cause more distress than their visible severity would suggest, which can make it hard to untangle cause and effect.³

Where cortisol fits in

The clearest evidence that stress hormones act on hair comes from animals. In a 2021 study in mice, corticosterone, the rodent equivalent of cortisol, controlled how long hair follicle stem cells stayed dormant. Chronically stressed mice had higher corticosterone and their follicles stayed in the resting phase for longer, while mice without the hormone went through more growth cycles over their lifetime.⁴ Mouse studies have also supported the long-held belief that stress can hold back hair growth and push follicles into regression.³

Laboratory work on human follicle cells points the same way. Corticotrophin-releasing hormone (CRH), the brain's signal that starts the stress response, has been reported to push follicles early into their regression phase and to slow growth of the hair shaft.⁵ High cortisol has also been proposed to break down substances the skin and follicle need. But a 2024 review of hormones and hair loss concluded that cortisol's role still remains unclear, and much of what it describes is hedged as possible rather than proven.⁵

In short, there is a plausible biological link between stress hormones and shedding, and good reason to think stress can trigger telogen effluvium. What has not been shown is that a measurable rise in a person's cortisol is what makes their hair fall out.

Your hair follicles make their own stress hormones

One reason the picture is complicated is that the follicle is not just on the receiving end. Human scalp hair follicles grown in the laboratory secrete substantial amounts of cortisol. They respond to CRH in a way that mirrors the body's main stress system, the hypothalamic-pituitary-adrenal (HPA) axis, including the feedback that switches cortisol production off again.⁶ Studies of cells from the base of the follicle suggest they can also make and respond to CRH.⁵

So the stress signals around a follicle may come partly from the bloodstream and partly from the scalp itself. That local system has also been studied in alopecia areata, the autoimmune condition that causes patches of hair loss. Higher levels of CRH and the pituitary hormone ACTH have been found in the scalp of people with it, although the review that reports this says the field needs further studies.⁵

Does high cortisol cause hair loss? What Cushing's syndrome shows

If raised cortisol alone caused hair loss, you might expect it to be a hallmark of Cushing's syndrome, the rare condition caused by too much cortisol. It is not. The NHS lists excessive hair growth (hirsutism) among the symptoms, alongside fat build-up on the tummy and upper back, a round red face, easy bruising, stretch marks, muscle weakness and irregular periods, and does not list hair loss.⁷ The most common cause of Cushing's syndrome is taking high doses of steroid medicines for a long time.⁷

Steroid medicines are also a standard treatment for alopecia areata,⁵ which is another reason "more cortisol means less hair" is too simple. People with Cushing's syndrome do have very high hair cortisol: in one study their average was 106.9 pg/mg, against 8.4 pg/mg in healthy volunteers.⁸ But a hair test does not diagnose Cushing's. If you have several of its symptoms, see a doctor; our guides to high cortisol symptoms and testing for Cushing's explain what happens next.

Can a hair cortisol test explain your hair loss?

Not on its own. A hair test measures your average cortisol over roughly the past three months. It can show whether your long-term cortisol has been high during that time: in a meta-analysis of 66 studies, hair cortisol was 22 per cent higher in groups exposed to chronic stress, rising to 43 per cent when the stress was ongoing.⁹ The same analysis found that hair cortisol did not consistently match how stressed people said they felt.⁹

What it cannot do is tell you why your hair is falling out. The 2024 review found there is not yet enough data to confirm the use of hair cortisol in people with hair loss.⁵ Timing adds a twist. Shedding starts about three months after a trigger,² and the centimetre of hair nearest the scalp reflects hair formed roughly 1.3 to 2.2 months before the cut.¹⁰ So a sample cut when you first notice shedding may partly cover the months when the trigger happened. A high result would tell you your cortisol was raised then. It would not prove that cortisol caused the shedding.

The causes a doctor is most likely to look for are different: blood tests can check for conditions such as thyroid disease and iron deficiency.² For more on long-term stress and cortisol, see cortisol and stress.

Taking a hair sample when your hair is thinning

Thinning hair does not usually rule out a hair cortisol test. Telogen effluvium thins hair across the whole scalp, and only in very severe cases does the scalp become visible.² A few practical points help:

• Pool small locks. If your hair is thin, take two or three small locks from neighbouring spots at the back of the head. In a 2026 study, pooled samples like this gave less variation within the same person than a single lock.¹¹
• Use cut hair, not shed hair. Hairs that have fallen out on a brush or pillow have already stopped growing, so they do not represent the most recent months. The sample must be cut at the scalp.
• Do not swap in body hair. In a study comparing the two, most hormones correlated only weakly between scalp and body hair, and the authors concluded body hair is not a suitable substitute.¹²
• Avoid patches. If you have patchy hair loss, cut from an area where the hair is growing normally.
• Mention scalp treatments. Steroid creams, lotions and other local steroids were linked to lower hair cortisone in a large Dutch cohort, so tell the laboratory about anything you apply to your scalp.¹³

The full steps are in how to take a hair sample.

When to see a GP about hair loss

The NHS suggests seeing a GP if you are worried about hair loss or it is affecting your wellbeing, and doing so before paying for a private hair clinic.¹ The British Association of Dermatologists advises seeing a doctor if shedding does not improve, to check for other causes.² See a doctor promptly if hair loss comes with other symptoms such as unexplained weight change, extreme tiredness or changes to your periods. Falling oestrogen around the menopause is another hormonal change linked to hair loss;⁵ cortisol and the menopause covers what happens to cortisol at that time.