Obsessive Compulsive Disorder

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Human Uniqueness Compared to "Great Apes": 
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Obsessive-compulsive disorders are a relatively well-defined group of conditions with some overlap with the anxiety states. Obsessions are repetitive thoughts that the individual does not want and tries to rid him or herself of. By contrast with some psychotic ("passivity") phenomena the thoughts are recognised as the individual's own. The element of resistance is essential to the diagnosis, and this is often accompanied by considerable distress. Compulsions are similar phenomena in the motor field eg door lock checking, hand washing and counting rituals, Each of these conditions is generally long-lasting, sometimes over a lifetime leading to the suspicion that the symptoms are somehow related to personality structure. A striking concomitant is difficulty in taking decisions.

Because they involve thoughts, and thoughts need to be put into words, and may necessarily be verbal, such phenomena cannot be reliably detected im other species. Repetitive behaviors can be observed and are often a consequence of captivity and confinement, But equally whether such behaviors have the same subjective accompaniments and symbolic significance cannot be determined.









Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Definite Appearance: 
100 thousand years ago
Background Information: 

Obsessive-compulsive disorders occur in all societies, probably at about the same frequency. They overlap with depressive/anxiety disorders on the one hand, and eating disorders on the other.

The Human Difference: 

The defining characteristic obsessive-compulsive disorders is that the source of the action is the patient's own, and that he tries to resist the repetition, but fails to do so. Because they lack language other primates cannot be shown to have similar phenomena, although they can be observed to engage in ritualistic behaviour.

Universality in Human Populations: 

As far as can be ascertained obsessive-compulsive disorders occur in all human populations, probably at about the same incidence.

Mechanisms Responsible for the Difference: 

Possession of language

Possible Selection Processes Responsible for the Difference: 

Speciation events between the common ape-hominin precursor and modern Homo sapiens.

Implications for Understanding Modern Humans: 

The occurrence of these phenomena add to our knowledge of the structure of language

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