-Barges in with an example.-
Miles Gunn, a former officer of the YSS Sakura and a Shoi in the Star Army of Yamatai, suffered from a severe case of post traumatic stress disorder. The result of his mental defect was that he had a homicidal episode when forced to transfer into a Yamataian body. The homicidal episode led to him attempting to kidnap Hanako, while attempting to kill the Sakura's MEGAMI. Unfortunately his attempt failed due to a NH28's intervention.
Poor guy, he was on his way to psychological treatment when he was ambushed, which resulted in his original body supposedly being irradiated beyond repair. Oh well, the Lorath fixed him better than ever. :3
There have been other examples of psychological disturbance; such as the physical mental defect found in Sana, or the suicidal tendency of Yosef, and the self inflicted headshot by this one character I can't remember.
Anyway, example session over.
PS: The Lorath provide excellent psychological treatments.