This chapter outlines and discusses both established and more recent psychological theories and explanations for the causes of terrorism. Since the terrorist attacks on the United States on 11 September 2001, a wealth of research on the causes and nature of terrorism has been published. Therefore a high level of selectivity in citation of work has been applied in order to make this chapter appropriately concise. Traditional theories of behaviour from academic psychology – social, cognitive and psychodynamic – can be applied to this phenomenon, but this chapter focuses in the main on those that have been applied directly to terrorism. As W. Reich (1990) states, we cannot understand the psychology of terrorism without understanding the socio-political conditions, religious beliefs and basic psychological mechanisms that allow humans to undertake acts contravening the morals that usually inhibit them. Reich (1990) argues that terrorism cannot be understood exclusively in psychological terms; it is necessary to take an interdisciplinary approach. The theoretical and practical importance of studying this field speaks for itself. At the present time, and with the advent of weapons of mass destruction and modern technology, international terrorism is threatening global security on a scale not seen before.

A lot of research on terrorism is focused on the Middle East and on Islam in particular, not because this part of the world and this religion are intrinsically linked to terrorism but because terrorism coming from this region and in the name of Islam has been very prominent in recent years.