Yet far from proving the effectiveness of ECT, the emerging research has only accentuated its unknowns and shortcomings. After more than 60 years of experience, doctors still don't know exactly how the shocks affect the brain, whether they cause permanent damage, or why they affect depression. Although the techniques and technology have improved, ECT itself appears no more effective than it ever was, studies show.

In several recent studies in rats, scientists have reported some of the first direct evidence of biological changes from the treatments that might be related to changes in behavior. They report that ECT accelerates the production of new brain cells in these animals and spurs the growth of neural connections called mossy fibers. Some ECT doctors say new neurons are probably helpful and that new nerve connections may enhance brain function.

In the first large-scale effort to learn from ECT patients themselves, researchers in England reviewed 35 studies of patient attitudes. All told, the studies involved more than 2,000 men and women who got ECT treatment in the last two decades or earlier. Depending on the study, 30% to 80% of former patients reported lasting memory loss. In one survey, a third of patients agreed with the statement, "Electroconvulsive therapy permanently wipes out large parts of memory." The proportion of people who considered the treatment ultimately helpful varied just as widely -- from about one- third, when patients helped design or conduct surveys; to about three-fourths, when doctors did.