In 2002, a study on cocaine addiction demonstrated measurable volume loss in several areas of the brain, including the frontal lobes. The study technique was an MRI-based protocol, voxel-based morphometry (VBM), where 1 mm cubes of brain are quantified and compared. Another VBM study was published in 2004 on methamphetamine, with very similar findings. While interesting, these findings may not be surprising to either the scientist or the layperson, as these are “real drugs” used illicitly. Nevertheless, it was noteworthy that addiction could produce measurable, anatomical change in the brain.
Even more instructive are similar findings seen with the abuse of a normal biological behavior, eating, leading to addiction and obesity. In 2006, a VBM study was published looking specifically at obesity, and the results were very similar to the cocaine and methamphetamine studies. The obesity study demonstrated multiple areas of volume loss, particularly in the frontal lobes, areas associated with judgment and control.
Growing evidence indicates that the VTA-NAc pathway and the other limbic regions cited above similarly mediate, at least in part, the acute positive emotional effects of natural rewards, such as food, sex and social interactions.
In one study, sexual experience has been shown to induce alterations in medium spiny neurons in the nucleus accumbens similar to those seen with drugs of abuse