Space madness
Space madness was a term for space-related insanity. There was more than one type. It was sometimes caused by contamination or exposure to various elements. 

In 2266, Spock posited that the insanity that had apparently led to the deaths of the Psi 2000 personnel could be a type of space madness heretofore unknown to them. ()

The crews of the  and later the  experienced a type of space madness after their exposure to the spatial interphase in 2269. Doctor Leonard McCoy described the "madness" as being caused by "the area of space we're in," and that "the molecular structure of the brain tissues in the central nervous system are distorting." ()

Psychological conditions