Hmmmmmm... According to wikipedia:
"Solipsism syndrome is a postulated condition which may be faced by those living in space or on another planet for extended periods of time.[1][2] It may be best described as 'severe Big Brother anomie'."
Solipsism as a philosophical position is that of thinking one's own mind is the only thing that can be known to be real. And some solipsists also actively believe that it really IS the only thing that's real, and that everything else is just fictional. Just images conjured up by THEIR own mind..
So it relates to that position. And apparently, according to the wikipedia page:
"Solipsism syndrome is, by extension, the overwhelming feeling that nothing is real, that all is a dream. Sufferers become lonely and detached from the world and eventually become completely indifferent.[3] Some people claim to have suffered from Solipsism Syndrome[4] but it is not currently recognized as a psychiatric disorder by the American Psychiatric Association.[5]"
..They are mostly worried that astronauts on long space travels, etc, might start suffering from it.
Most interesting. :)
I have a friend who I actually think showed certain symptoms of this at some point, even though she is not an astronaut.