Terrorist behavior represents a subtype of human aggression probably determined by a combination of biological, psychological, and social factors, as well as by peculiar environmental influences and group dynamics. As regards terrorists' psychological characteristics, the available studies (mostly carried out with no sound scientific design) have failed to identify the common or typical pathological personality traits of modern terrorists. The popular opinion that terrorists must be insane or psychopathic is still widespread; however, no evidence exists that terrorist behavior may be caused either by prior or current psychiatric disorders or psychopathy. Not surprisingly, some theories have proposed social factors and non-pathological psychological traits as predisposing elements for terrorist acts, but they generally lack of empirical validation. Moreover, most of these theories do not explain why, even if so many people are exposed to the same social factors or show the same psychological traits, only a tiny minority of them join a terrorist group. Therefore, it is mandatory that systematic and scientific investigations be carried out in order to understand the possible bases for terrorist aggression, including the early detection of possibly associated psychopathology, and to design an appropriate counterterrorism prevention policy.
Keywords: Terrorism; modern terrorists; personality disorders; psychiatric disorders; psychopathology.