Findings that women are as violent as men have been termed "gender symmetry".
A 32-nation study of university students "revealed an overwhelming body of evidence that bidirectional violence is the predominant pattern of perpetration; and this study, along with evidence from many other studies (Medeiros & Straus, 2007), indicates that the etiology of PV is mostly parallel for men and women."
Straus and Gelles found that in couples reporting spousal violence, 27% of the time the man struck the first blow; in 24% of cases, the woman initiated the violence. The rest of the time, the violence was mutual, with both partners brawling
. The results were the same even when the most severe episodes of violence were analyzed. In order to counteract claims that the reporting data was skewed, female-only surveys were conducted, asking females to self-report, and the data was the same. The simple tally of physical acts is typically found to be similar in those studies that examine both directions, but some studies show that male violence may be more serious. Male violence may do more damage than female violence; women are more likely to be injured and/or hospitalized. Female partners are more likely to be killed by their male partners than the reverse (62.1% to 37.9% per Department of Justice study), and women in general are more likely to be killed by their spouses than by all other types of assailants combined. From a data set of 6,200 cases of spousal abuse in the Detroit area of the US in 1978-79, a study found that men used weapons 25% of the time while female assailants used weapons 86% of the time; 74% of men sustained injury and of these 84% required medical care
. Other studies report that female perpetrated domestic abuse is more common than male among adolescents.