OCD. OCD is obsessive compulsive disorder, which is comprised of obsessions (repeating unwanted thoughts) and compulsions (ritualistic behaviors to help deal with those thoughts) such as washing hands repeatedly, constantly cleaning, checking locks, and other similar behaviors. Often the emotions behind OCD are based in fear and/or anger that is unresolved and even unverbalized.
When Severe Enough. I assume you are asking if a person suffering from OCD could be considered disabled. Ocd can present in different ways such as germ phobias, counting rituals, etc. The symptoms of OCD can vary in their intensity from very mild causing little distress to severe leaving an individual housebound and unable to care for themselves. These individuals are clearly disabled.