Medieval treatment for mental illness included one of the following, a. cutting off limbs b. drilling hole in skull to let spirits out c. consuming gold compounds such as gold salts d. diet consisting of raw vegetables only

B drilling holes in the skull because they believed the person was possessed by unholy matter

Because without physical activity, the body has extra "energy" if you will, and so when it is time for bed you are not tired, so you end up staying up all night. also there is probably an effect on your internal clock, which messes with your melatonin production which goes hand in hand with your sleep cycle