Imaging the brains of 10 young men who were long term users of ecstasy and seven of their healthy peers with no history of ecstasy use has revealed a significantly smaller hippocampus in those who used ecstasy. The overall proportion of gray matter was also lower, suggesting the effects of ecstasy may not be restricted to the hippocampus.

Both groups had used similar amounts of recreational drugs other than ecstasy, and drank alcohol regularly. The ecstasy group had not taken ecstasy for more than two months before the start of the study on average.