Mood and personality changes are common after hysterectomy regardless of whether or not one or both ovaries are removed. But additionally, ovarian function is oftentimes impaired after the uterus is removed. Our organs work together as a system... remove part of the system and it doesn't work properly. The ovaries of women with all their parts produce health promoting hormones their whole lives.
Ovary removal and post-hysterectomy impaired ovarian function have been shown to increase risk for a number of health problems. Unfortunately, most gynecologists are not honest with women about this. If they were, there would be far fewer hysterectomies and oophorectomies (big money makers for gynecologists).