Along with its sense of euphoria, ecstasy has long been thought of as damaging to users' brains. But a recent study led by a team at Harvard Medical School has revealed there is no evidence that ecstasy causes brain damage. Harvard Professor John Halpern said previous studies tested ecstasy users for whom all-night dancing and raves were a lifestyle, resulting in sleep and fluid deprivation—factors that alone are known to have lasting cognitive effects. Non-users in the same studies were selected from a different cultural background and skewed research results. He also said that past studies have not factored in the other drugs and alcohol that ecstasy users may have also been taking. "Essentially we compared one group of people who danced and raved and took ecstasy with a similar group of individuals who danced and raved but who did not take ecstasy. When we did that, we found that there was no difference in their cognitive abilities."