This video will discuss whether there is any truth to the old wive's tale that your hair grows faster when you're asleep compared to when you're awake. I will cover what happens to your body during activation of the sympathetic ("fight or flight") and parasympathetic ("rest and digest") nervous systems, also whether there are any documented cases of patients with sleep disorders also experience unusual upregulation or suppression of hair growth. I also briefly explain the difference between correlation and causation. Royalty-free music by Kevin MacLeod (incompetech.com) What I'm wearing: Tartan CS-411 overbust by Orchard Corset (review to come at a later date)