Dilemma on genes' role in diseases

Genes that contribute to alcoholism, Alzheimer's and depression have been discovered and this could lead to new types of treatments for these diseases. The question is: will people want to know that they have them?

This potential difficulty was raised at the genetics conference yesterday by Prof Mike Conneally, director of the division of hereditary diseases and family studies at Indiana University, who is originally from Ballygar, Co Galway.

These "complex disorders" had a significant genetic component but they were not like other inherited diseases, such as cystic fibrosis.

Alcoholism, Alzheimer's and depression also had a strong environmental component, Prof Conneally explained and so having the relevant genes did not always mean disease would occur.

Alcoholism was the most common psychiatric disorder, he said, although its incidence here was no higher than in most other countries. About one in 10 of the population here developed alcoholism and it was thought that about 40 per cent of susceptibility was related to gene function. "It is a major genetic disorder."

Children of alcoholics are significantly more likely to develop the disease than families unaffected by alcoholism, he said, and this was also seen in children given up for adoption who would not have experienced the disease as a part of home life.

Between 18 per cent and 40 per cent of adopted children of alcoholics also developed the disease, depending on the type involved. "We are attempting to find the genes for alcoholism," Prof Conneally said.

Similar work was under way in manic depression, which occurred in about 1.3 per cent of the total population and in ordinary depression, which occurred in about 7 per cent of people.

The likelihood of developing either disorder rose significantly if other family members suffered from the diseases, he said. Children who had two parents with the disease faced a 50/50 chance of also developing depression.

Researchers had now identified four genes associated with Alzheimer's disease, Prof Conneally said, but this raised questions about what to tell a person about their future health. Having certain genes meant that a person was virtually certain to develop the disease in middle age.

"Very few want to know if they have the genes," Prof Conneally said. He doubted that "when the chips are down" most people would want such information.