Obsessive-compulsive disorder as a disturbance of security motivation: constraints on comorbidity.

Patients with OCD often meet criteria for additional psychiatric disorders, with the incidence of comorbidity being as high as 75% in some studies. Here we examine the theoretical plausibility that in OCD much of the domain of co-morbid presentations encompasses related perturbations of the security motivation system. According to a recent proposal, the security motivation system represents a biologically primitive special motivation that is activated by potential (as opposed to imminent) danger to self or intimate others and engages a set of specialized species-typical behaviors (such as checking and washing) to handle potential danger. Because the task of security motivation is open ended, in the sense that no consummatory stimuli can exist in the real world to indicate the absence of potential danger, the shutdown of security motivation is produced by a self-generated feeling of knowing, a satiety signal termed yedasentience. In this schema, OCD results from a failure to generate or respond to the yedasentience signal: without this negative feedback the patient persists abnormally long in a strong motivational state having to do with primal, basic threats to existence, a condition that leads to prolonged engagement in security-related behaviors, such as the checking and washing, characteristic of OCD compulsions and obsessions. Considering the proposed neuronatomy of security motivation system and OCD, we discuss the likelihood that the phenomenon of "spread of allied reflexes" can produce other security-related psychiatric conditions, as well as the possibility that disturbances along different pathways of the security motivation system can lead to apparently different disorders.