Previous studies have shown that chronic and severely stressful situations, such as depression or posttraumatic stress disorder, may correspond to smaller volumes in "stress sensitive" brain regions, such as the cingulate region of the cerebral cortex and the hippocampus, a brain region involved in memory formation.  Ellemarije Altena, ,from the Royal Netherlands Academy of Arts and Sciences (Amsterdam, The Netherlands), and colleagues used a specialized technique called voxel-based morphometry, to evaluate the brain volumes of individuals with chronic insomnia who were otherwise psychiatrically healthy, and compared them to healthy persons without sleep problems. The researchers found that insomnia patients had a smaller volume of gray matter in the left orbitofrontal cortex, which was strongly correlated with their subjective severity of insomnia. Explaining that: “This is the first voxel-based morphometry study showing structural brain correlates of insomnia and their relation with insomnia severity,” the team urges that: “Functional roles of the affected areas in decision-making and stimulus processing might better guide future research into the poorly understood condition of insomnia.”