I think if a person was a lifelong JW and found him or herself in the position of being shunned, they could very well succumb to the kind of loneliness and isolation that could trigger depression and depending upon their age, even send them into early onset dementia.
Life long JW's often don't have the skills or courage to go out and make new friends. On top of that, they may actually still believe that worldly people are all evil and the world is going to end any minute. They may believe they deserve to be punished and often their self worth is at a low ebb just when they need it the most.