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OCD Explained

By: , Posted on: July 22, 2015

Obsessive-compulsive disorder (OCD) is characterized by repetitive thoughts, impulses, or images that are intrusive and inappropriate and cause anxiety or distress, or repetitive behaviors that the person feels driven to perform in response to an obsession or rigid rules that must be applied. Those suffering from this condition recognize that the obsessions are a product of their own mind. The obsessions or compulsions are time consuming or interfere with role functioning.


Obsessions are defined as recurrent, persistent thoughts, images, or impulses that are experienced as intrusive and inappropriate.

Compulsions are repetitive behaviors (e.g., checking locked doors or gas jets, hand washing) or mental acts (e.g., counting, repeating words) that the person feels driven to perform in response to an obsession or according to rigid rules.

Obsessive-compulsive disorder (OCD) is a chronic illness dominated by obsessions and compulsions occurring in the absence of another psychiatric disorder (Goodwin and Guze, 1996).


Previously classified as an anxiety disorder, the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) (American Psychiatric Association, 2013) classifies OCD as one of the Obsessive-Compulsive and Related Disorders.

The ICD-10 (International Statistical Classification of Diseases and Related Health Problems, 10th revision) describes 5 subtypes of OCD: predominantly obsessional thoughts or ruminations; predominantly compulsive acts (obsessional rituals); mixed obsessional thoughts and acts; other obsessive-compulsive disorders; obsessive-compulsive disorder, unspecified.

Obsessions is defined as: 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; the thoughts, impulses, or images are not simply excessive worries about real life problems; the person attempts to ignore or suppress such thoughts, impulses, or images, or to neutralize them with some other thoughts or action; and the person recognizes that the obsessional thoughts, impulses, or images are a product of his or her own mind (not imposed from without as in thought insertion).

Compulsions as defined as: repetitive behaviors (e.g., hand washing, ordering, checking) or mental acts (e.g., praying, counting, repeating words silently) that the person feels driven to perform in response to an obsession, or according to rules that must be applied rigidly; and 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 At some point during the course of the disorder, the person recognizes that the obsessions or compulsions are excessive or unreasonable.

The obsessions or compulsions cause marked distress, are time consuming (take more than 1 hour a day), or significantly interfere with the person’s normal routine, occupational (or academic) functioning, or usual social activities or relationships.


Obsessive-compulsive disorder (OCD) is a potentially disabling condition that can persist for life. The individual who suffers from OCD becomes trapped in a pattern of repetitive thoughts and behaviors that are senseless and distressing but extremely difficult to overcome. OCD may be mild to severe. If severe and left untreated, OCD can destroy the capacity to function at work, at school, or even at home.

About 20% to 30% of OCD patients have significant improvement in their symptoms, 40–50% display moderate improvement, and the remaining 20–40% either remains ill or experience a worsening of symptoms (Sadock and Sadock, 2003).

Associated Disorders

Obsessive-compulsive disorder (OCD) frequently co-occurs with other conditions. The association with major depressive disorder is particularly prominent, although comorbidity with panic disorder, phobias, and eating disorders is also common. Finally, OCD exhibits a particularly interesting association with Tourette’s disorder – approximately half of all patients with Tourette’s disorder meet criteria for OCD, although less than 10% of patients with OCD meet criteria for Tourette’s disorder.


Many clinical drug trials support the hypothesis that a dysregulation of the serotonergic system is involved in the symptom formation of obsessions and compulsions in this condition. Thus, serotonergic drugs are more effective therapies for this condition than agents that affect other neurotransmitter systems. However, it is unclear whether alterations in serotonergic transmission are directly responsible for Obsessive-compulsive disorder (OCD) (Sadock and Sadock, 2003). Brain imaging experiments, such as positron emission tomography (PET) studies, have revealed an increased activity (metabolism and blood flow) in the frontal lobes, the basal ganglia (especially the caudate), and the cingulum of patients with OC D. Effective pharmacological and behavioral treatments reportedly reverse these abnormalities ( Sadock and Sadock, 2003). Genetic studies support the hypothesis that OCD has a significant genetic component. Studies reveal a higher concordance rate for monozygotic than for dizygotic twins. Family studies of these patients indicate that 35% of the first-degree relatives of OCD patients are also afflicted with the disorder ( Sadock and Sadock, 2003). Behavior factors. According to learning theorists, obsessions are conditioned stimuli. A relatively neutral stimulus becomes associated with fear or anxiety through a process of respondent conditioning by being paired with events that are by nature noxious or anxiety producing. Compulsions are established in a different way. It is theorized that when a person discovers that a certain action reduces anxiety attached to an obsessional thought, active avoidance strategies in the form of compulsions or ritualistic behaviors are developed to control the anxiety ( Sadock and Sadock, 2003). Psychodynamic aspects. According to Sigmund Freud, OCD is an obsessive-compulsive neurosis associated with a regression from the oedipal phase to the anal psychosexual phase of development ( Sadock and Sadock, 2003).


The lifetime prevalence for OCD in the general population is estimated at 2% to 3%. Thus, OCD is more common than schizophrenia, bipolar disorder, or panic disorder. OCD strikes people of all ethnic groups, with males and females being equally affected. The mean age of onset is in the mid-20s to early 30s (Sadock and Sadock, 2003).


The discovery that medications that increase serotonergic transmission in the central nervous system are efficacious in obsessive-compulsive disorder revolutionized its treatment and suggested that the pathophysiology of this condition is related to changes in serotonin function.

Read More about OCD in the below SciTech Connect article:

Neurobiology Basis of OCD

This excerpt was taken from the article Obsessive–Compulsive Disorders by B. Levant. The article examines consequences, associated Disorders, etiology and therapies of OCD.

This article was exclusively written for the Reference Module in Biomedical Sciences which provides extensive authoritative and up-to-date knowledge in the interdisciplinary field of Biomedical Sciences. Articles are reviewed continuously and once deemed out-of-date, they are updated exclusively for the Reference Module, as this article Obsessive–Compulsive Disorders was. Learn More Here.

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