A qualified clinician will be able to diagnose obsessive compulsive disorder based on the following criteria. These criteria are put forth by the world health organization and are popularly known as the ICD (international classification of diseases) criteria. Considerable clinical expertise is required in order to ascertain the presence or absence of criteria in a potential sufferer.
For a definite diagnosis, obsessional symptoms or compulsive acts, or both, must be present on most days for at least 2 successive weeks and be a source of distress or interference with activities. The obsessional symptoms should have the following characteristics:
a) they must be recognized as the individuals’ own thoughts or impulses;
b) there must be at least one thought or act that is still resisted unsuccessfully, even though others may be present which the sufferer no longer resists;
c) the thought of carrying out the act must not in itself be pleasurable (simple relief of anxiety is not regarded as pleasure in this sense);
d) the thoughts, images, or impulses must be unpleasantly repetitive.
Further depending upon one’s symptom preponderance, the following specifiers may also be added to the diagnosis.
F42.0 Predominantly obsessional thoughts or ruminations
F42.1 Predominantly compulsive acts [obsessional rituals]
F42.2 Mixed obsessional thoughts and acts
F42.8 Other obsessive-compulsive disorders
F42.9 Obsessive-compulsive disorder, unspecified
Post a diagnosis, certain instruments, such as the YBOCS (Yale Brown Obsessiveness compulsive scale) may be used to quantify the severity of the illness.