Interstellar Cognitive Deterioration Syndrome

It took centuries before it was fully understood and could be treated.
Known in the medical world as the Interstellar Cognitive Deterioration Syndrome or ICDS, it's a condition that some humans seem to get once they pass beyond the influence of Sol. it is believed that the effect of travelling beyond the heliosphere of the sun is, despite the centuries of research in the area, is still poorly understood throughout the years, treatments have been developed, but at the same time a notable decrease in humans suffering from ICDS or "Space craze" as its commonly known and some theories are that due to the increased travel across the border of our solar system, the human race has rapidly developed some resistance to the condition.
Some of the symptoms one would experience if they got space craze would be hallucinations, light paranoia and in some cases claustrophobia. It's not a deadly condition to have; in most cases, it will pass by itself after some days.
Some of the early ways to reduce the risk of the crews and or passengers getting the craze would be for the entire ship except for a skeleton crew to enter into hibernation before the transition through the area. The downside to this method was that it required a large amount of sleeping pods and as those were still in early development back when humans began to cross the stars in bigger numbers, it quickly got too expensive to move new colonists to their new home.
The solution came once the first FLT drive was invented and became common use on ships, as it was now possible to ignore the region altogether and simply jump past it.  of course FLT came with its own conditions and troubles but compared to the craze those were mild as most cases of sickness from FTL are reports of nausia, headaches and the like.