''Right now, I'm not embarrassed of who my mother was,'' she said. ''I'm embarrassed of the society I live in. She was a sick woman, and people made it a joke.''

Schizophrenia, which can give rise to visual and auditory hallucinations, severe mood swings and incoherent behavior, is believed to afflict 1 percent of adults and usually manifests itself in men by their late teens or early 20's and women by their mid-20's.

Although doctors have yet to pinpoint its cause, and have weighed such possibilities as abnormal prenatal development, viral infection and environmental influences, much of their research in recent years has focused on hereditary factors. ''It's clearly a familial illness, and it appears to involve abnormal genes,'' said Dr. Jack M. Gorman, a professor of psychiatry at Columbia University.

Dr. Gorman said that an estimated 10 percent of people with schizophrenia commit suicide, often motivated less by their delusions than by the despair they feel in lucid moments. Psychiatrists said the higher incidence of suicide in Ms. Ray's family might be explained by the fact that people with loved ones who commit suicide are more likely to see it as an option for themselves.

Schizophrenia can frequently be managed with drugs, but getting people with the illness to stay on their medication can be difficult. That was certainly true of Ms. Ray.

Her relatives said that Ms. Ray did not like the side effects of some drugs, which caused lethargy or weight gain. She often convinced herself that there was nothing wrong with her and that there was no need to take the medication. In addition, she missed the grandiose self-image that came with her delusions, her mother said.

''It made her feel important,'' Ms. Duvall said. ''She enjoyed that.''

Mr. Letterman said that in between Ms. Ray's uninvited visits to his house over the years she sent him many letters, and it was obvious from each whether she was taking her drugs. ''When she was on them,'' he said in a recent telephone interview, ''it was like hearing from your aunt. When she was off them, it was like hearing from your aunt on Neptune.''