Biological research into the cause of eating disorders has found some evidence for a genetic or hereditary component based on the finding that, if one identical twin suffers from anorexia nervosa, the other twin will also develop this disorder in as many as percent of cases. the concordance rate for fraternal twins, on the other hand, is only around 20 percent.

The correct answer is 70%.

Explanation:

Eating disorder or binge eating is a psychological problem however anorexia nervosa an eating disorder runs in families too. It indicates that it has something to do with genetic or intercity component. Recent researchers have found 2 genes involved in determining the chances of acquiring the eating disease. It suggests that genes have also an important role in such cases. Research on twins found that 70% chances to develop the case in other twin.

Thus, the correct answer is 70%.