Physical violence is an important health problem, especially among males [1]. The development of physical aggression has been studied with large population based longitudinal studies from birth to adulthood. Results show that children start using physical aggressions by the end of the first year after birth, increase their frequency from 2 to 4 years of age [2]–[5], and then reduce the frequency from school entry to adulthood [6]. However, a minority of children (4–7%), mainly males, maintain a high frequency of physical aggression from childhood to adolescence [5]–[7]. These children tend to be impulsive, hyperactive, oppositional and rejected by their peers, they also tend to fail in school and have serious social adjustment problems during adulthood [8]–[12]. There is good evidence that the parents of children on a high trajectory of physical aggression exhibit similar behavioral problems creating early childhood family environments which do not support learning to regulate physically aggressive reactions [5], [7], [13]–[16].
