Most astrophysicists thought wormholes should not exist except in black holes. They defy science known up to the date of their discovery, and continue to create all sorts of logical paradoxes. Scientists, however are not the only ones to get headaches over thoughts of wormhole travel. The worst are reserved for those who actually travel through wormholes. There are few certainties about what is happening to the human mind as it instantly enters then instantly leaves wormhole space.
Doctors know that jump travel can cause nausea, vomiting, dizziness, loss of balance, mild to severe visual and sonic hallucinations, temporary memory loss, and even short-term paralysis. They also know that these effects are nearly 100% psychosomatic. The mind is what is feeling disoriented and disturbed.
The debate rages as to what happens to the mind. One of the most respected theories is that the mind suffers the effects of "vertical time ."
What is vertical time? Essentially, time continues! to operate in wormholes, but it is not the same timeline that the rest of the universe operates on. If a ship enters a wormhole 10:59 and 23 seconds, it will exit the wormhole at 10:59 and 23 seconds. No time has passed for the ship. However, on another timeline, drawn as a vertical line on a graph, the ship may "travel" for centuries in the wormhole before arriving in the new star system. Therefore, jump drives propel ships into a different dimension of time.
The people aboard ship do not age in this time. In fact, they are held in suspended animation. Only their minds sense that centuries have passed at all. When they return to their own time, in new star system, their minds remember the centuries passing while trapped motionless in instant of real time.
Some come out of the experience mildly disoriented and a bit punch-drunk. Others get very dizzy and sick, taking hours to recover. Most have nightmares of being trapped in a motionless hell. The very unlucky ones end up with a severe case of madness, on par with paranoid schizophrenia. The really scary folks are the ones that actually like it.
source: Terran & Avarian Fleet Book