Chronic psychotropic drug treatment may lead to structural remodeling of the brain. However, the clinical significance and details of these structural changes is not yet clear. Because exectuing studies to evaluate this issue is difficult in humans, a group of researchers at King's College London developed a rat model to study psychotropic drugs. They administered either lithium or haloperidol (a common antipsychotic) to rats in doses equivalent to those received by humans and tracked structural changes with MRI. Gray matter was decreased by 6 percent after haloperidol treatment, but increased by 3 percent after lithium treatment. "Whether these changes in brain structure underlie the benefits or side effects of these medications remain to be seen," commented John Krystal, Editor of Biological Psychiatry. "However, they point to brain effects of established medications that are not well understood, but which may hold clues to new treatment approaches."