A new study has tentatively answered a century-old question: does poverty cause mental illness, or does mental illness cause people to drift down the economic ladder?

Depression appears to be a consequence, not a cause of poverty, according to a researcher at the New York State Psychiatric Institute.

The stress of fighting discrimination as they battle their way up from poverty leaves formerly poor people more depressed and anti-social than their middle-class neighbors, said Bruce P. Dohrenwend, chief of the department of social psychiatry at the psychiatric institute.

But another type of mental illness, schizophrenia, dooms the person by his genes to a life of instability and economic problems, no matter where on the economic ladder he starts, Mr. Dohrenwend and researchers at the Hadassah University Hospital in Jerusalem reported in a recent issue of Science.

The researchers studied 4,914 Israeli-born adults between the ages of 24 and 34 of European North Africa and Muslim backgrounds.