not sure if this counts, but whilst breaking into and sheltering in MAes Howe, 2 vikings went mad:

"Earl Harald set out for Orkney at Christmas with four ships and a hundred men. He lay for two days off Graemsay, then put in at Hamna Voe on Mainland (Stromness), and on the thirteenth day of Christmas they travelled on foot over to Firth. During a snow storm they took shelter in Maeshowe and there two of them went insane, which slowed them down badly, so that by the time they reached Firth it was night-time."