Obsessive-Compulsive Disorder (OCD) is an anxiety disorder where a person has recurrent and unwanted ideas or impulses (called obsessions) and an urge or compulsion to do something to relieve the discomfort caused by the obsession. The obsessive thoughts range from the idea of losing control, to themes surrounding religion or keeping things or parts of one's body clean all the time. Compulsions are behaviors that help reduce the anxiety surrounding the obsessions. Most people (90%) who have OCD have both obsessions and compulsions. The thoughts and behaviors a person with OCD has are senseless, repetitive, distressing, and sometimes harmful, but they are also difficult to overcome.

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Obsessive-compulsive disorder (OCD) is a psychiatric anxiety disorder most commonly characterized by a subject's obsessive, distressing, intrusive thoughts and related compulsions (tasks or "rituals") which attempt to neutralize the obsessions.

The typical OCD sufferer performs tasks (or compulsions) to seek relief from obsession-related anxiety. To others, these tasks may appear odd and unnecessary. But for the sufferer, such tasks can feel critically important, and must be performed in particular ways to ward off dire consequences and to stop the stress from building up. Examples of these tasks: repeatedly checking that one's parked car has been locked before leaving it; turning lights on and off a set number of times before exiting a room; repeatedly washing hands at regular intervals throughout the day.

Symptoms may include some, all, or perhaps none of the following:

Repeated hand washing.
Repeated clearing of the throat, although nothing may need to be cleared.
Specific counting systems — e.g., counting in groups of four, arranging objects in groups of three, grouping objects in odd/even numbered groups, etc.
One serious symptom which stems from this is "counting" steps — e.g., feeling the necessity to take 12 steps to the car in the morning.
Perfectly aligning objects at complete, absolute right angles, or aligning objects perfectly parallel etc. This symptom is shared with OCPD and can be confused with this condition unless it is realized that in OCPD it is not stress-related.
Fear of acting out on violent or aggressive impulses, or feeling overly responsible for the safety of others.
Sexual obsessions or unwanted sexual thoughts. Two classic examples are fear of being homosexual or fear of being a pedophile. In both cases, sufferers will obsess over whether or not they are genuinely aroused by the thoughts.
Strange and chronic worries about certain events such as sleeping, eating, leaving home, etc without proper items. An example would be one who literally can't fall asleep without a metronome.
Having to "cancel out" bad thoughts with good thoughts. An example of this would be imagining harming a child and having to imagine a child playing happily to cancel it out.
A fear of contamination (see Mysophobia); some sufferers may fear the presence of human body secretions such as saliva, blood, sweat, tears, vomit, or mucus, or excretions such as urine or feces. Some OCD sufferers even fear that the soap they're using is contaminated.[6]
A need for both sides of the body to feel even. A person with OCD might walk down a sidewalk and step on a crack with the ball of their left foot, then feel the need to step on another crack with the ball of their right foot. If one hand gets wet, the sufferer may feel very uncomfortable if the other is not. If the sufferer is walking and bumps into something, he/she may hit the object or person back to feel a sense of evenness. These symptoms are also experienced in a reversed manner. Some sufferers would rather things to be uneven, favoring the preferred side of the body.
An obsession with numbers (be it in math class, watching TV, or in a room). Some people are obsessed with even numbers and loathe odd numbers (odd numbers cause them a great deal of anxiety and often make the person uncomfortable or even angry) or vice versa.
Twisting the head on a toy around, then twisting it all the way back exactly in the opposite direction (see even body section).
Fear of transformation. A fear of transforming into someone or something else. Losing ones self or taking on undesired characteristics is what creates the anxiety and fear. Rituals such as counting, blinking, checking, hand washing etc. may eliminate the anxiety when they are done in a way which "feels right" to the sufferer.
In some cases, a pattern of uniformity on a bank account may indicate obsessive-compulsive spending. For example, an OCD-affected figure skater may issue a check to his/her coach for a private lesson every week, paying the same amount each time. In addition, the affected person may feel complacent about or invincible against the economic issues.
There are many other possible symptoms, and one need not display those above to suffer from OCD. Formal diagnosis is performed by a mental health professional. Furthermore, possessing the symptoms above is not an absolute diagnosis of OCD.

OCD sufferers are aware that such thoughts and behavior are not rational[citation needed], but feel bound to comply with them to fend off feelings of panic or dread. Because sufferers are consciously aware of this irrationality but feel helpless to push it away, untreated OCD is often regarded as one of the most vexing and frustrating of the major anxiety disorders.[citation needed]

In an attempt to further relate the immense distress that those afflicted with this condition must bear, Barlow and Durand (2006) use the following example.[7] They implore readers not to think of pink elephants. Their point lies in the assumption that most people will immediately create an image of a pink elephant in their minds, even though told not to do so. The more one attempts to stop thinking of these colorful animals, the more one will continue to generate these mental images. This phenomenon is termed the "Thought Avoidance Paradox”, and it plagues those with OCD on a daily basis, for no matter how hard one tries to get these disturbing images and thoughts out of one's mind, feelings of distress and anxiety inevitably prevail. Although everyone may experience unpleasant thoughts at one time or another, these are usually warranted concerns that are short-lived and fade after an adequate time period has lapsed. However, this is not the case for OCD sufferers.[8]

Obsessive-compulsive disorder is often confused with the separate condition obsessive compulsive personality disorder. The two are not the same condition, however. OCD is ego dystonic, meaning that the disorder is incompatible with the sufferer's self-concept. Because disorders that are ego dystonic go against an individual's perception of his/herself, they tend to cause much distress. OCPD, on the other hand, is ego syntonic—marked by the individual's acceptance that the characteristics displayed as a result of this disorder are compatible with his/her self-image. Ego syntonic disorders understandably cause no distress. Persons suffering from OCD are often aware that their behavior is not rational and are unhappy about their obsessions but nevertheless feel compelled by them. Persons with OCPD, by contrast, are not aware of anything abnormal about themselves; they will readily explain why their actions are rational, and it is usually impossible to convince them otherwise. Persons with OCD are ridden with anxiety; persons who suffer from OCPD, by contrast, tend to derive pleasure from their obsessions or compulsions.[9] This is a significant difference between these disorders.

Equally frequently, these rationalizations do not apply to the overall behavior, but to each instance individually; for example, a person compulsively checking their front door may argue that the time taken and stress caused by one more check of the front door is considerably less than the time and stress associated with being robbed, and thus the check is the better option. In practice, after that check, the individual is still not sure, and it is still better in terms of time and stress to do one more check, and this reasoning can continue as long as necessary.

Some OCD sufferers exhibit what is known as overvalued ideas. In such cases, the person with OCD will truly be uncertain whether the fears that cause them to perform their compulsions are irrational or not. After some discussion, it is possible to convince the individual that their fears may be unfounded. It may be more difficult to do ERP therapy on such patients, because they may be, at least initially, unwilling to cooperate. For this reason OCD has often been likened to a disease of pathological doubt, in which the sufferer, while not usually delusional, is often unable to fully realize what sorts of dreaded events are reasonably possible and which aren't.

OCD is different from behaviors such as gambling addiction and overeating. People with these disorders typically experience at least some pleasure from their activity; OCD sufferers do not actively want to perform their compulsive tasks, and experience no pleasure from doing so.

OCD is placed in the anxiety class of mental illness, but like many chronic stress disorders it can lead to clinical depression over time. The constant stress of the condition can cause sufferers to develop a deadening of spirit, a numbing frustration, or sense of hopelessness. OCD's effects on day-to-day life—particularly its substantial consumption of time—can produce difficulties with work, finances and relationships.

There is no known cure for OCD as of yet, but there are a number of successful treatment options available.

Some cases are thought to be caused at least in part by childhood streptococcal infections and are termed PANDAS (Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections). The streptococcal antibodies become involved in an autoimmune process. Though this idea is not set in stone, if it does prove to be true, there is cause to believe that OCD can to some very small extent be "caught" via exposure to strep throat (just as one may catch a cold). However, if OCD is caused by bacteria, this provides hope that antibiotics may eventually be used to treat or prevent it.[11]

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