AS THE TWENTY-FIRST CENTURY approaches, great progress is being made in the study of mental illnesses. The future promises to bring new insights, better treatments, perhaps even cures. At the same time, society continues to wrestle with the personal and social effects of mental illnesses. As in the past, people are trying to balance the rights of the mentally ill with those of others in society.

The quest for causes and cures

Continuing research has produced breakthroughs in understanding the possible causes of mental illnesses. New technology has allowed scientists to study the structure and biochemistry of the brain in far greater detail than ever before. As a result, there is a renewed emphasis on the biological theories of mental illness.

Scientists have found differences in the physical makeup of people with mental disorders. Some people with mental illnesses have abnormal levels of certain...