A case study reveals that a 24-year old software professional in India developed blinding headaches every time he watched x-rated videos.

Researchers from Guru Gobind Singh Indraprastha University in New Delhi said that the headaches developed only when he watched videos and not during sex or masturbation.
He was then treated by a team of neurologists who were baffled by his condition before suggesting that the headaches could have caused by pain-sensing nerves in the face and jaw which become sensitive during “heightened emotional state associated with viewing pornography”. He was also advised to take ibuprofen and paracetamol around 30 minutes before watching such videos.
Source-Medindia