Temporal narcosis was a condition whereby one experienced overwhelming neurophysical stress when entering another time continuum, in much the same way deep sea divers experienced nitrogen narcosis.
In 2369, Captain Jean-Luc Picard experienced temporal narcosis shortly after boarding the USS Enterprise-D, which had become trapped in a temporal fragment. Succumbing to this condition, Picard alternately experienced states of hysteria and panic, before being beamed out of the fragment's influence. (TNG: "Timescape")
In 2377, a male patient aboard the Dinaali Hospital Ship 4-2 had temporal narcosis delirium. (VOY: "Critical Care")