Hormones
Running on empty: what sleep loss and cortisol do to the follicle
Every mum in clinic has been told, by someone, that her hair is falling out because she is stressed. It is half true, unhelpfully put, and it lets everyone off the hook — because the stress is not optional.
What cortisol does
Cortisol is the hormone of running on empty: broken sleep, no recovery, the mental load that never switches off. In the follicle it does something specific. It shortens the growth phase and pushes follicles into rest early. It also narrows the small vessels that supply the follicle and turns up low-level inflammation in the scalp. Three of the five things that keep a follicle quiet, all driven by one hormone.
Why it shows up late
A follicle pushed into rest does not release its hair immediately; it holds it for two to three months and then lets go. So the shed you see in September is the spring you had. This delay is why the cause is so hard to see, and why women blame whatever is happening the month the hair falls.
Why it is worse in the years after children
Cortisol does more damage to a follicle that has already lost its oestrogen shield. Before children, a bad six months would produce a shed that fully recovered. After children, with the shield thinner, the same six months leaves some follicles quiet. The stress did not cause the pattern on its own; it exposed follicles that were already vulnerable.
Not sure which one is you?
Take the two-minute hair quiz
Twelve quick questions. We tell you what we think is going on, what to do about it, and we say so if it is something we cannot help with.
Start the quiz →The stress is a load. The hormones decide how much of it the follicle can carry.
What actually helps
Not “reduce your stress”. Three things that are within reach: protect the first ninety minutes of sleep, because that is when growth hormone peaks and the follicle repairs; eat protein and iron at breakfast rather than at the end of the day, because the follicle is built from what arrives in the morning; and address the scalp directly — supply, inflammation and signalling can be worked on at the follicle even while the cortisol carries on, which for most mums is the only realistic option.
And rule out the things that look like stress and are not: ferritin and thyroid, which produce the same picture and are far easier to fix.
Ready to read your own pattern?
Take the two-minute hair quiz
Twelve questions. We tell you what we think is going on for you, and we say so if it is something a GP should see first.
Start the quiz →
