首页 | 主题 | 图库 | 问答 | 文摘 | 原创 | 百科

历史 | 地理 | 人物 | 艺术 | 体育 | 科学 | 音乐 | 电影 | 信息技术 | 世界遗产

 开放、中立,源自维基百科

Personal tools

Obsessive-compulsive disorder

From Wikipedia, the free encyclopedia

Jump to: navigation, search
Obsessive-compulsive disorder
Classification & external resources
DiseasesDB = 33766
ICD-10 F42.
ICD-9 300.3
eMedicine med/1654 
MeSH D009771

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 phrase "obsessive-compulsive" has worked its way into the wider English lexicon, and is often used in an offhand manner to describe someone who is meticulous or absorbed in a cause (see "anal retentive"). Such casual references should not be confused with obsessive-compulsive disorder; see clinomorphism. It is also important to distinguish OCD from other types of anxiety, including the routine tension and stress that appear throughout life. Although these signs are often present in OCD, a person who shows signs of infatuation or fixation with a subject/object, or displays traits such as perfectionism, does not necessarily have OCD, a specific and well-defined condition.

To be diagnosed with obsessive-compulsive disorder, one must have either obsessions or compulsions alone, or obsessions and compulsions, according to the DSM-IV-TR diagnostic criteria. The Quick Reference to the diagnostic criteria from DSM-IV-TR (2000) describes these obsessions and compulsions:[1]

Obsessions are defined by:

  1. Recurrent and persistent thoughts, impulses, or images that are experienced at some time during the disturbance, as intrusive and inappropriate and that cause marked anxiety or distress.
  2. The thoughts, impulses, or images are not simply excessive worries about real-life problems.
  3. The person attempts to ignore or suppress such thoughts, impulses, or images, or to neutralize them with some other thought or action.
  4. The person recognizes that the obsessional thoughts, impulses, or images are a product of his or her own mind, and are not based in reality.

Compulsions are defined by:

  1. Repetitive behaviors or mental acts that the person feels driven to perform in response to an obsession, or according to rules that must be applied rigidly.
  2. The behaviors or mental acts are aimed at preventing or reducing distress or preventing some dreaded event or situation; however, these behaviors or mental acts either are not connected in a realistic way with what they are designed to neutralize or prevent or are clearly excessive.

In addition to these criteria, at some point during the course of the disorder, the sufferer must realize that his/her obsessions or compulsions are unreasonable or excessive. Moreover, the obsessions or compulsions must be time-consuming (taking up more than one hour per day), cause distress, or cause impairment in social, occupational, or school functioning.[1] OCD often causes feelings similar to those of depression.

Contents

Causes and related disorders

It was the general belief in 14th, 15th, and 16th century Europe that those who experienced blasphemous, sexual, or other obsessive thoughts were possessed by the Devil. Based on this reasoning, treatment involved banishing the "evil" from the "possessed" person through exorcism.[2]

Today the community of scientists studying obsessive-compulsive disorder is split into two factions disagreeing over the illness's cause. One side believes that obsessive-compulsive behavior is a psychological disorder; the other side thinks it has a neurological origin. A majority of researchers now believe in this neurological hypothesis.

The Stanford University School of Medicine OCD webpage states, "Although the causes of the disorder still elude us, the recent identification of children with OCD caused by an autoimmune response to Group A streptococcal infection promises to bring increased understanding of the disorder's pathogenesis."[3]

Psychological explanations

Freud

In the early 1910s, Sigmund Freud attributed obsessive-compulsive behavior to unconscious conflicts which manifested as symptoms.[2] Freud describes the clinical history of a typical case of "touching phobia" as follows:

After it has started, in early childhood, the patient shows a strong desire to touch, the aim of which is of a far more specialized kind than one would have been inclined to expect. This desire is promptly met with an external prohibition against carrying out that particular kind of touching. The prohibition is accepted, since it finds support from powerful internal forces, and proves stronger than the instinct which is seeking to express itself in the touching. In consequence, however, of the child's primitive physical constitution, the prohibition does not succeed in abolishing the instinct. Its only result is to repress the instinct (the desire to touch) and banish it into the unconscious. Both the prohibition and instinct persist: the instinct because it has only been repressed and not abolished, and the prohibition because, if it ceased, the instinct would force its way through into consciousness and into actual operation. A situation is created which remains undealt with—a psychical fixation—and everything else follows from the continuing conflict between the prohibition and the instinct.[4]

Biological explanations

There are many different theories about the cause of obsessive-compulsive disorder. The majority of researchers believe that there is some type of abnormality in the neurotransmitter serotonin, among other possible psychological or biological abnormalities; however, it is possible that this activity is the brain's response to OCD, and not its cause. Serotonin is thought to have a role in regulating anxiety, though it is also thought to be involved in such processes as sleep and memory function. This neurotransmitter travels from one nerve cell to the next via synapses. In order to send chemical messages, serotonin must bind to the receptor sites located on the neighboring nerve cell. It is hypothesized that OCD sufferers may have blocked or damaged receptor sites that prevent serotonin from functioning to its full potential. This suggestion is supported by the fact that many OCD patients benefit from the use of selective serotonin reuptake inhibitors (SSRIs) — a class of antidepressant medications that allow for more serotonin to be readily available to other nerve cells.[5] For more about this class of drugs, see the section about potential treatments for OCD.

Recent research has revealed a possible genetic mutation that could be the cause of OCD. Researchers funded by the National Institutes of Health have found a mutation in the human serotonin transporter gene, hSERT, in unrelated families with OCD. Moreover, in his study of identical twins, Rasmussen (1994) produced data that supported the idea that there is a "heritable factor for neurotic anxiety".[6] In addition, he noted that environmental factors also play a role in how these anxiety symptoms are expressed. However, various studies on this topic are still being conducted and the presence of a genetic link is not yet definitely established.

Another possible genetic cause of OCD was discovered in August 2007 by scientists at Duke University Medical Center in North Carolina. They genetically engineered mice that lacked a gene called SAPAP3. This protein is highly expressed in the striatum, an area of the brain linked to planning and the initiation of appropriate actions. The mice spent three times as much time grooming themselves as ordinary mice, to the point that their fur fell off.[7]

Technological advancements have allowed for the possibility of brain imaging. Using tools like positron emission tomography (PET scans), it has been shown that those with OCD tend to have brain activity that differs from those who do not have this disorder.[8] This suggests that brain functioning in those with OCD may be impaired in some way. A popular explanation for OCD is that offered in the book Brain Lock by Jeffrey Schwartz, which suggests that OCD is caused by the part of the brain that is responsible for translating complex intentions (e.g., "I will pick up this cup") into fundamental actions (e.g., "move arm forward, rotate hand 15 degrees, etc.") failing to correctly communicate the chemical message that an action has been completed. This is perceived as a feeling of doubt and incompleteness, which then leads the individual to attempt to consciously deconstruct their own prior behavior — a process which induces anxiety in most people, even those without OCD.

It has been theorized that a miscommunication between the orbitofrontal cortex, the caudate nucleus, and the thalamus may be a factor in the explanation of OCD. The orbitofrontal cortex (OFC) is the first part of the brain to notice whether or not something is wrong. When the OFC notices that something is wrong, it sends an initial "worry signal" to the thalamus. When the thalamus receives this signal, it in turn sends signals back to the OFC to interpret the worrying event. The caudate nucleus lies between the OFC and the thalamus and prevents the initial worry signal from being sent back to the thalamus after it has already been received. However, it is suggested that in those with OCD, the caudate nucleus does not function properly, and therefore does not prevent this initial signal from recurring. This causes the thalamus to become hyperactive and creates a virtually never-ending loop of worry signals being sent back and forth between the OFC and the thalamus. The OFC responds by increasing anxiety and engaging in compulsive behaviors in an attempt to relieve this apprehension.[5] This overactivity of the OFC is shown to be attenuated in patients who have successfully responded to SSRI medication. The increased stimulation of the serotonin receptors 5-HT2A and 5-HT2C in the OFC is believed to cause this inhibition. [1]

Some research has discovered an association between a type of size abnormality in different brain structures and the predisposition to develop OCD. Through the use of magnetic resonance imaging (MRI), researchers at Cambridge's Brain Mapping Unit were able to discover distinctive patterns in the brain structure of individuals with OCD and their close family members. [2] This is the first instance in which it has been demonstrated that those with a familial risk of developing OCD have anatomical differences when compared with ordinary individuals. The discovery of these structural differences in the area of the brain associated with stopping motor response may ultimately aid researchers who seek to determine which genes contribute to the development of OCD. In the future it might also provide more objective criteria for diagnosing the disorder.

Symptoms and prevalence

OCD is manifested in a variety of forms.

Community studies have placed the prevalence between one and three percent, although the prevalence of clinically recognized OCD is much lower, suggesting that many individuals with the disorder are unaccounted for clinically.[9] The fact that many individuals do not seek treatment may be due in part to stigma associated with OCD. Another reason for not seeking treatment is because many sufferers of OCD do not realize that what they are suffering from is OCD, mainly because the typical depiction of the disorder in the media and elsewhere only covers a few of the many symptoms of OCD.

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 are 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, or repeatedly washing hands at regular intervals throughout the day.

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

Languages
AD Links