Defensive and appetitive motivation systems have evolved to propitiate more sophisticated interactions with environment threats and needs, such as nutrients, water, reproduction, and temperature regulation. In contact with survival-relevant environmental stimuli, organisms change as a whole to maximize fitness to that occasion. In this paper, an overview on defensive systems is described, as well as some relevant aspects of defensive states, including their impacts over appetitive functions. A parallel between these characteristics and what is called threat-related disorders in the present paper is drawn and, finally, these similarities are used as basis for a theoretical proposition that at least part of these disorders can be seen as persistent states of defense.