Multiple Personality Disorder is not a modern diagnosis anymore. It is not categorized as " Dissociative Identity Disorder." The psychological community is no longer in agreement over whether it actually exists. Some believe that it’s a tactic people with borderline personality disorder use.
People with borderline personality disorder have extreme mood swings. They have rapid changes in self-identity and goals. I had a friend (I had to cut off the friendship eventually) with this disorder. She couldn’t keep a steady job and kept moving. She’d get mad at people and impulsively quit her jobs. I’m not even sure how she kept getting new jobs so fast. But she was constantly in a state of having another new job and being unemployed. Her religion kept switching a lot too as did her political viewpoints. Our friendship was toxic because she’d continually accuse me of not wanting to spend time with her, screening her phone calls, and talking behind her back. Then she’d just disappear. I didn’t even know it was a test. When it started happening, we weren’t that close of friends. I just stopped seeing her at the place we usually bumped into each other. I didn’t even know she had my phone number. But she called me up one day and told me she’d been in the hospital and began crying about how all her friends had abandoned her . . . and then after some sobbing “Even you…but I’ve forgiven you.”
This became the regular pattern of our relationship. All her behavior was oriented around everyone being horrible people who hated her and didn’t authentically care about her. She’d be friendly for you for a period, but it’s a definite relationship of “I hate you, but don’t leave me!”
Disassociative identity disorder is where someone views (or claims to view) their mood swings and rapidly changing identities as different people. The point is, they are dissassociating from their actions to deny moral responsibility.
It’s important to understand that mental illness isn’t like a disease in the biological sense. The “illnesses” are a list of traits that usually go together. Their mood disorders when such thought patterns and destructive behaviors aren’t occupied by every aspect of their life. It’s a personality disorder when the thought patterns and behavior is pretty constant in every area of your life.
People with mental illnesses are trapped. So this reduces their moral culpability to their sins. Their actions are still objectively sinful. Sadly, as someone struggling with mental health issues, the frustrating thing I have with confession is priests don’t want to hear any sins connected to mental illness. So they’ll just keep telling me “That’s not a sin.” I end up with nothing to confess because my there isn’t a single sinful choice I make that isn’t rooted in mental illness.