Obsessive-compulsive disorder (OCD) is a common anxiety disorder. It is characterized by recurrent, bothersome mental or behavioural habits. "Obsessions" are recurrent, unwelcome thoughts or images, and "compulsions" are habitual behaviours (physical actions or sequences of thoughts) which often relieve the anxiety induced by obsessions. The symptoms can arise at almost any time in life, but often begin during childhood or during young adulthood. The symptoms often wax and wane over time, sometimes changing slightly from one type to another, sometimes becoming worse during stressful situations.
There are certain types of symptoms that are most common:
1) obsessive concern about germs or dirt, leading to compulsive washing
-this pattern can become so extreme that hours of the day can be spent cleaning, hands getting badly chapped from overwashing; there can be a lot of avoidance of situations (e.g. crowds, public transit, washrooms, shaking hands with people) where there may be a perceived abundance of germs
2) obsessive doubt, leading to compulsive checking
-those with this symptom frequently feel that they have made a mistake--sometimes a catastrophic mistake such as having left the oven on, or having hit someone with their car--leading to a compulsive need to go back and check to make sure this hasn't happened. A lot of time can be wasted going back to check and re-check. Often times people with this symptom realize their behaviour is irrational or excessive, but the feelings are so strong that they can't stop the pattern.
3) obsessive or compulsive symmetry: a need to assess the symmetry of things, or to make things symmetric. Sometimes there may be a need to do an activity (e.g. brushing teeth, or tying shoes) in a very particular way, and if something interrupts the behaviour, the symptom makes the person want to go back and start again from the beginning. A related symptom is a feeling of needing to count things in multiples, or do things a certain number of times (e.g. things have to be in threes).
4) obsessional thoughts: often these are thoughts about doing something forbidden or inappropriate; they often have a violent or sexual nature, and can be hard for people to talk about (people can be embarrassed or ashamed at having the thoughts). Symptomatic people often will interpret their thoughts as evidence that they are not safe or that they are losing their mind. The symptom can lead to avoidance of many situations (e.g. if the obsessional thought is about doing something aggressive, it may lead to avoidance of being around other people).
There are many other varieties of obsessions & compulsions, and it can be helpful to read an educational book on the subject. The OCD Workbook by Bruce Hyman is a good example.
There are two types of therapy that help most with OCD:
Cognitive-behavioural therapy is extremely important and has been shown to work. The main principles here are to educate oneself about OCD, to be able to recognize and pronounce the symptoms as they occur (i.e. to recognize in one's mind that "this is an OCD symptom, not a sign of insanity or dangerousness"), to stop oneself from doing the compulsive behaviours, and to practice exposure to situations that induce the symptoms (e.g. for the germ phobic person, the exposure therapy may be spending time with bare hands scooping soil in a garden).
Antidepressant medications which act on the serotonin system in the brain also reduce OCD symptoms.
Typically, any treatment for OCD reduces symptoms by about 30%. For some people the treatments work much better. Often times, combinations of therapy techniques, continued for longer periods of time, are needed to tame the symptoms more completely.