Aggression is common in many neuropsychiatric diseases, such as dementia, autism spectrum disorder, and schizophrenia. It causes many problems for patients and their families, but can be difficult to treat because little is known about what causes it. In a study published last month in Molecular Psychiatry, researchers from the University of Tsukuba revealed that variation in levels of interleukin 1β (IL-1β), a protein that mediates the inflammatory response, is associated with individual differences in aggressive behaviors in male mice.