The COVID-19 pandemic has raised all our stress levels. A new study has shown why the long-term effects of stress can include hair loss and has even suggested directions for research into reversing this effect.
With the list of long-COVID symptoms growing each day, one surprising figure stands out: nearly a quarter of people who get COVID-19 experience hair loss within the next six months. This likely isn’t a result of the virus worming its way into our hair follicles from our lungs and nose but is probably due to the effects of stress brought on by infection and recovery.
COVID-19 infection isn’t the first stressful scenario to produce this particular response: chronic stress has long been linked to hair loss, but the reason behind the association has been hard to pin down. A new study published in Nature has now shown in detail the molecular events leading to stress-induced hair loss in mice.
Hair today, gone tomorrow
Our hair cycles through several stages during our life – a growth phase called anagen, a degeneration phase called catagen and a resting phase, known as telogen.
In the growth phase, hair follicle stem cells (HFSCs) are instructed to start dividing, a process that, through several stages of differentiation, ultimately leads to the formation of a hair shaft that emerges from our skin. Over the course of the other two phases, growth stops, and the stem cells stop dividing. In this dormant phase, hair eventually falls out, kickstarting a new phase of growth under normal conditions.
In some cases of severe stress, a huge number of cells leap into the telogen (resting) phase at once, leading to sudden hair loss. To study what was provoking this shift, a team of scientists led by senior author Ya-Chieh Hsu, professor of stem cell and regenerative biology at Harvard University, blocked the effects of chronic stress by removing the adrenal glands that produce stress hormones from mice.
This, Hsu tells Technology Networks, provoked an unexpected reaction: “The real surprise came when we depleted stress hormones. Under normal conditions, hair follicle regeneration slows over time – the resting phase becomes longer as the animals age. But when we removed the stress hormones under unstressed normal conditions, the stem cells’ resting phase became extremely short and the mice constantly entered the growth phase to regenerate new hair follicles and hairs throughout their life, even when they were old.”
Without any adrenal glands, levels of the key mouse stress hormone corticosterone had plummeted. When these mice were shaved, their hair follicles hopped into the growth phase roughly three times as often as the …….