Difference between obsession and compulsion

• Sometimes anxiety and tension are associated with obsessions—persistent unwanted thoughts, impulses or ideas or compulsions—seemingly irrational behaviours repeatedly carried out in a fixed, repetitive way.

• People with obsessive-compulsive disorders find their obsessions or compulsions distressing and debilitating but feel unable to stop them.
• The compulsive actions are usually carried on to alleviate the anxiety caused by obsessions. A person provoked with anxious thoughts may try to block them out by compulsively counting steps while walking. Another person obsessed with the idea that he is guilty or dirty, may wash his hands every few minutes, sometimes till the bleed.
• The symptoms of OCD include a contamination - an obsession of contamination followed by washing or compulsive avoidance of the object. Shame and disgust and the feeling of being easily contaminated are common. Patients usually believe that the contamination is spread from object to object or person to person by the slightest contact.
(a) Pathological Doubt—Obsession of doubt followed by the compulsion of checking. Patients have an obsessional self-doubt and are always feeling guilty about having forgotten something. The checking may involve multiple trips back to the house to check the stove.

(b) Intrusive Thoughts—repetitive thoughts of a sexual or aggressive act that is reprehensible to the patient. This is usually not followed by compulsions.