Obsessive-compulsive disorder (OCD) is a chronic mental illness that involves obsessional thoughts or compulsive acts. The main categories of OCD involve checking, contamination, hoarding, and ruminations or intrusive thoughts. Investigators still unable to find the exact cause for the obsessive-compulsive disorder.

Some investigators suggest the involvement of certain chemicals such as serotonin. Risk factors for OCD include certain genetic factors, brain structure issues, certain environmental factors, stressful life situations, and presence of other mental health disorders such as tic disorders.

Many pathophysiological theories and hypotheses carried the responsibility of explaining the pathophysiology of OCD such as serotonin hypothesis, the dopamine hypothesis, the autoimmune hypothesis, and other neurobiological hypotheses.

Signs and symptoms of the obsessive-compulsive disorder usually include both obsessions and compulsions. Obsessions can involve certain symptoms such as excessive fear of contamination, extreme violent thoughts, and unreasonable need for reassurance all the time. Compulsion signs and symptoms may include repetitive hand-washing or repetitive words, phrases, or religious prayers.

A psychiatrist may use certain criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) to diagnose OCD. In addition, he/she may perform a physical exam, psychological evaluation, or may suggest certain lab tests. The typical treatment for OCD is medication and psychotherapy.

Issues such as possible side effects and chemical interactions should carefully be considered when choosing medications for OCD. If not properly treated, OCD could lead to several complications such as physical damages and social unemployment.

Most people with OCD show improvement with treatment but a completely symptom-free period is improbable to occur. In many western countries, OCD is considered the fourth most common mental illness that may affect all people regardless of their gender, race, age, religion, nationality or socio-economic group.

Obsessive-compulsive disorder (OCD) is defined as a common, chronic and long-lasting type of mental illness that featured by repeated obsessional thoughts or compulsive acts. The unreasonable obsessions (thoughts and fears) can lead to repetitive compulsions (behaviors and acts).

Obsessions are known as repeated or persistent thoughts, ideas, or mental images, while, compulsive behaviors are known as repetitive, rigid, and self-directed habits that are performed as an attempt to make obsessions go away. OCD is common disorder among adults, adolescents, and children all over the world.

The majority of researchers are investigating four main categories of obsessive-compulsive disorder (OCD).Every category has numerous sub-types that could be investigated separately.  The four main categories are:

• Checking: The repetitive urge to check is the compulsion, the obsessive fear is mostly about preventing damage, fire, leaks or harm. Examples of checking include:

1. Home’s doors and windows checking to prevent thoughts regarding robbery and stealing
2. Water taps checking to prevent thoughts regarding damaging or flooding the house.
3. Gas or electric checking to prevent thoughts regarding explosions and house burning.
4. Memory checking to confirm that the intrusive thought is just a thought in mind and did not materialize in real life.
5. Repetitive reading of words or lines in a book again and again to prevent thoughts regarding partial understanding or missing important information from the book.
6. Turning off the lights in the house to prevent thoughts of house burning.
7. Obsessive checking of wallet or purse to prevent thoughts regarding missing important IDs or valuable cards).
8. Constant checking of illnesses symptoms to prevent thoughts regarding illness development
9. Repetitive calling and texting of certain people to prevent thoughts regarding an actual harm happened to them.
10. Constant fear that obsessive–compulsive disorder symptoms will lead to schizophrenia symptoms

• Contamination / mental Contamination: In this case, the compulsion is the need to clean and wash, the obsessive fear is that something is contaminated and/or illness or death is the outcome if contamination not prevented perfectly. Examples may include :

1. Refusing to contact with chemicals out of fear of contamination.
2. Refusing to enter public toilets because of obsessive thoughts of germs contracting.
3. Refusing to visit hospitals to prevent contracting germs from other people.
4. Refusing the usage of public telephones to prevent contracting germs from other people.
5. Refusing to eat in a public restaurant or cafe to prevent contracting germs from other people.
6. The fear of being in a crowd of people because of obsessive thoughts of germs contracting.
7. Fear of red objects and stains that mimic blood appearance because of obsessive thoughts of contracting HIV/AIDS.
8. Prolonged tooth brushing because of obsessive thoughts regarding the development of mouth disease.
9. Shaking one’s clothes to remove dead skin cells to prevent contamination.
10. Mental Contamination: The feelings of mental contamination occur when physical or mental abusive remarks directed toward a person to encourage him/her to develop the feeling of internal filthiness even in the absence of any physical contact with a dangerous/dirty object.  Unlike the contact contamination, the source in this case is always human not inanimate objects. However, the person will try to clean the dirt by repetitive showering and washing.

• Hoarding: Defined as the inability to discard useless or worn out possessions. Hoarding can be considered as a distinct disorder or as a symptom of another disorder.
• Ruminations/ Intrusive Thoughts: In the spectrum of OCD, rumination is defined as an episode of prolonged thinking about an issue or subject that is purposeless and fruitless, while, intrusive thoughts, in the context of OCD, are obsessional thoughts that can cover any subject and featured by being horrific, recurrent, disturbing and exotic. The common subcategories are:

1. Relationship intrusive thoughts: The main concern for this type of obsessional thoughts is the excessive skepticism over the one’s relationship suitability or one’s partner or one's own sexual desire. Such thoughts may include questioning one’s own sexuality, questioning the faithfulness of one's partner, and doubt the depth of feelings for one's partner.
2. Body-focused obsessions: Symptoms that related to this type of OCD may include the questioning whether breathing is shallow or deep, obsessive blinking, and hyperawareness of particular body parts such as perception of a particular side of the nose while reading.
3. Sexual intrusive thoughts: The main concerns for these obsessional thoughts include ideas of unintentional sexual harm directed toward certain groups of people (e.g. children) or the constant doubts of one’s own sexual orientation.   Such thoughts may include fearing t involvement in incest relationships, imagining of being a paedophile, and intrusive sexual thoughts concerning religious figures such as deities, angels, or saints.
4. Magical thinking/ thought-action fusion: This kind of thinking is about increasing the likelihood of event merely by thinking about it. Also, magical thinking can involve the mental linking of unrelated events.People with this kind of thinking attempt to drive it away by performing peculiar and time-consuming magical rituals. Examples of magical thinking include believe in sinister/good meaning of certain color, number, or days; also, believe that death is approaching when attending a funeral may be considered magical thinking.
5. Religious intrusive thoughts/ scrupulosity: Such thoughts may include believing in unforgivable sins by god and inevitability of hell, fear of practicing prayers in an inappropriate manner, or believe that intrusive bad thoughts that emerge during prayer will corrupt and scorn the prayer.
6. Violent intrusive thoughts: This is the type when unreasonable concern from carrying out particular violent acts against loved ones or other people manifested. Such thoughts may include fearing of killing or hurting innocent people or putting a toxic substance in the food of loved ones.
7. Symmetry and Orderliness: In this case, the compulsion is the urge to have everything lined up symmetrically. The obsessive fear might be to make sure that everything feels perfect to prevent the occurrence of discomfort or harm. Related examples include a desire to see everything spotless, neat and in its particular place at all times.

There are other disorders that may be part of obsessive-compulsive disorder or associated with it such as:

• Body dysmorphic disorder (BDD): People with this illness are overly disturbed with thinking that they are not beautiful enough, or part of their body is not normally shaped.
• Trichotillomania: This condition occurs when the person continually pulls his/her hair resulting in bald patches.
• Hypochondriasis: This condition occurs when the person develops an excessive fear of having a critical disease.
• Tourette syndrome: The reported symptoms of this disorder include tics, uncontrollably uttering words, and jerky movements.
• Anorexia nervosa: Obsessive-compulsive disorder is reported often to accompany this eating disorder. In such cases, the compulsive behavior focuses on limiting food intake and thinness.

Investigators still unable to find the exact cause for the obsessive-compulsive disorder. Some investigators suggest the involvement of the chemicals in the brain that transmit messages between nerve cells. Serotonin chemical is a prominent candidate.

Different patterns of brain activity have been shown in brain scans of many people with obsessive-compulsive disorder.It is possible that the disorder may results from certain changes occurred in the neuronal circuitry within a certain part of the brain called striatum.

Risk factors that facilitate the development of OCD including:

• Genetics: Although the exact genes still undetermined yet, it still probable that OCD has a genetic component within it. According to various twin and family studies, the likelihood of developing OCD increases in individuals with first-degree relatives (such as a parent) who suffer from OCD.
• Brain Structure and functioning:  Certain abnormalities in the chemical component of the body or brain functions may lead to OCD. Significant changes in the frontal cortex and subcortical structures of the brain in patients with OCD have been noticed by many imaging studies. The connection between OCD symptoms and abnormalities in certain areas of the brain have been noticed but more research is required to explain the exact process.
• Environmental factors: The possibility of developing the disease increases in people who abused physically or sexually in childhood as well as the people who had other trauma. Infections is another environmental factor that may play a role in triggering OCD.
• Stressful life situations: Exposure to traumatic or stressful events may increase the risk of developing the disease. Certain rituals, intrusive thoughts, and emotional distress may be triggered by some daily life stressors.
• Other mental health disorders: Other mental health disorders associated with OCD include anxiety disorders, tic disorders, substance abuse, and depression. Furthermore, the OCD is known sometimes as a sign of certain neurological conditions include frontotemporal dementia, cancer, or as a result of brain trauma.

There are many hypotheses attempt to explain the pathophysiology of OCD such as the serotonin hypothesis, the dopamine hypothesis, the autoimmune hypothesis, and other neurobiological hypotheses.

The serotonin hypothesis tries to regard the cause of OCD to an abnormality in serotonergic neurotransmission.The evidence supports this hypothesis derived from proven clomipramine efficiency in inhibiting both serotonin and norepinephrine reuptake and deceasing OCD symptoms. The pathogenesis of obsessive-compulsive phenomenology has been located in the basal ganglia where significant interaction between serotonin and dopamine occur. Other investigators suggest neuroendocrine mechanisms in the pathogenesis of obsessions and compulsions.

These perspectives argue for more involvement for oxytocin, vasopressin, and somatostatin in the process, but these arguments still need more sufficient experimental evidence. Part of the autoimmune hypothesis discussing a proposed correlation between infection with hemolytic Streptococcus types or other bacterial/viral agents, and the onset of OCD in some children.

The actual value of this hypothesis still not fully determined because the number of childhood-onset cases of OCD that related to this autoimmune process still unknown. Many investigators suggest the involvement of another neurobiological mechanism such as a dysfunction in the basal ganglia, orbitofrontal cortex, and striatum which can be treated effectively.

The genetic component in OCD cases can be manifested by various twin and family studies which advocate the idea that OCD can be inherited, although a positive family history cannot be confirmed in many cases.

Signs and symptoms of the obsessive-compulsive disorder usually include both obsessions and compulsions. Obsessions can involve certain symptoms such as:

• Excessive fear of contamination, germs, and infections. Also, refusing to touch objects touched by others because of fear of contamination.
• Focusing on particular words, sounds, images, or even numbers all the time.
• The extreme desire to see certain things symmetrical and perfectly ordered.
• An exaggerated feeling of disgust from bodily waste or fluids.
• Extreme thoughts and ideas about harming oneself or others.
• Thinking that an assigned work has been done imperfectly, although the patient knows this is not true.
• Unacceptable and unpleasant religious, sexual, and violent thoughts and subjects.

• Obsessive doubts that the doors are unlocked or the stove did not turn off
• Unreasonable need for reassurance all the time.
• Thoughts about speaking offensive words or acting inappropriately.
• Noticeable avoidance of situations that can trigger obsessions including shaking hands.
• Excessive fear of evil and sinful thoughts.

Themes associated with compulsions include:

• Repetitive hand-washing until the skin affected 
• Repetitive checking doors to make sure they are locked and stove to make sure it turned off
• Collecting newspapers or mails and saving them even if they become useless.
• Counting numbers in peculiar patterns
• Repetitive words, phrases , or religious prayers in a silent manner
• Arranging packaged stuff to face the same way
• Demanding reassurances, and following a strict routine

It is rare for OCD patients to have only one or two symptoms because the majority of them develop both obsessions and compulsions.

A diagnosis of obsessive-compulsive disorder (OCD) may depend mainly upon symptoms, medical history, and physical exam.

• Diagnostic criteria: The trained psychiatrist may use criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published by the American Psychiatric Association or another proper criterion. The diagnostic criteria for OCD that mentioned by American Psychiatric Association in (DSM-5) include:

• Presence of obsessions, compulsions, or both: Obsessions are defined as repetitive and persistent thoughts, images, or urges that result in considerable anxiety or distress in the experiencers when the disturbance occurs. The experiencers try to ignore or suppress these thoughts and images or to neutralize them by performing certain acts (compulsions). Compulsions are defined as repetitive behaviors such as hand washing or mental acts such as praying that performed by the experiencers in response to an obsession or according to certain principles that should be applied strictly. The reason behind performing these behaviors is to prevent some terrifying situation or to reduce anxiety or distress.The logical fabric of these behaviors or mental acts is not connected with what they are intended to neutralize or to prevent. 
• The obsessions or compulsions are requiring or wasting much time, sometimes it exceeds 1 hour every day, or can result in clinically apparent anxiety or abnormal changes in social, occupational, or other life aspects.
•  The obsessive-compulsive symptoms are not related to any recognizable effects of a particular substance (drugs or medications).Also, obsessive-compulsive symptoms must not be related to other medical disorders.
• Excluding the presence of other mental disorder which can explain the observed disturbance better than OCD such as hoarding disorder or trichotillomania.

The10th Edition of The International Classification of Diseases applies the following criteria to OCD:

1. On most days for a period of at least two weeks, either obsessions or compulsions (or both) must be observed.
2. The source of obsessions and compulsions must be internal (originating in the mind of the patient), not external (resulting from intervention or manipulation of other persons).
3. Obsessions and compulsions must be repetitive and unwanted and at least one excessive or unreasonable obsession or compulsion must be observed.
4. The patient must show resistance to obsessions and compulsions, although resistance to some obsessions or compulsions may be decreased in the long run.  One unsuccessfully resisted obsession or compulsion must be observed.
5. Noticing distress or interference with the one’s social or personal functioning usually can be the result of time wasting.
6. Having an obsessive thought or compulsive act is unwanted and generates no pleasure.

• Physical exam: Physical examination help determining whether other problems causing the observed symptoms and can be able to point out to any related complications.
• Psychological evaluation: Mental health care provider may apply a mental health assessment, which performed to assess the memory, the emotional functioning, and the ability to think and to use of reason. It also could involve tests to assess the nervous system as well as talking to the family or friends after taking the permission from the patient.
• Lab tests: A complete blood count (CBC) test can be suggested by mental health care provider, also, a check for the thyroid function and screening for alcohol and drugs can be recommended in many cases.

Early treatment for OCD is preferable and strongly recommended. The typical treatment for OCD is medication and psychotherapy. Often, treatment is most effective with a combination of these.

• Psychotherapy: The most effective type of psychotherapy for OCD called exposure and response prevention, which is a type of cognitive-behavioral therapy. Many evidence-based studies showed the effectiveness of exposure and response prevention in reducing compulsive behaviors in OCD, even in sufferers who show disappointing results to serotonin reuptake inhibitors. Exposure and response prevention involves a sequence of exposure to a feared object or obsession, such as dirt, and allowing the patient to learn certain and healthy ways to cope with resulted distress and anxiety.
• Medications: Medications that used to help reduce OCD symptoms include serotonin reuptake inhibitors (SRIs) and selective serotonin reuptake inhibitors (SSRIs). Clomipramine is a good example of a medication that has been proven effective in both adults and children with OCD.Also, WHO considers clomipramine as an essential drug for obsessive-compulsive and panic disorders. Clomipramine belongs to an older class of “tricyclic” antidepressants. Other newer “selective serotonin reuptake inhibitors” (SSRIs), including:

1. Paroxetine (for adults only)
2. Fluoxetine
3. Fluvoxamine
4. Sertraline

The patient may start to feel improvement within 1 to 3 weeks after taking an SSRI, but, improvement may take as many as 12 weeks to be well observed. However, it is rare to prove that using medication alone can effectively relieve OCD symptoms. The following issues are must be taken seriously when using medications to treat OCD:

1. The best choice of a medication: Controlling symptoms at the lowest possible dosage is considered the major goal here. Several drugs may be prescribed and tried before determining the best choice.
2. Side effects: Physician must be informed of any emerging side effects, noticing that all psychiatric drugs have significant side effects.
3. Suicidal tendencies: Most antidepressants have proven safe,  but in some children, teenagers and young adults under 25 may suicidal thoughts and behaviors have been reported in the first few weeks from taking antidepressants. A physician must be informed when noticing suicidal thoughts.
4. Interactions with other substances: Physician must be informed of any other prescription or over-the-counter medications, herbs or other supplements. Critical reactions with significant consequences have been reported between some antidepressants and certain medications or herbal supplements.

1. Antidepressants withdrawal: Sometimes physical dependence can develop after taking antidepressants for too long. Therefore, stopping treatment abruptly or missing several doses can result in withdrawal-like symptoms. Patient must not discontinue his medication before informing the physician.

• Family Therapy: Family therapy is often recommended due to the fact that OCD can result in problems in family life and social adjustment. Family therapy enhances patient’s understanding of the disease and can help reduce conflicts among other family members.
• Group Therapy: Group therapy is helpful treatment for OCD. Group therapy can provide support and encouragement and decreases feelings of isolation by creating proper interaction with other people with OCD.
• Neurosurgery: The surgery remains as an option for those who desperately ill and show no positive results when performing other treatment options. Many issues have to be considered before deciding the time of the surgery such as risks, benefits, and long-term postoperative management.
• Other treatment options: Deep brain stimulation (DBS) have been studied by many researchers to determine the potential effectiveness of this method in treating OCD cases that show negative responses to other treatment methods. This method uses surgically implanted electrodes in the brain as well as performing magnetic stimulation of certain parts of the brain.

The type of obsessions or compulsions determines the long-term complications of OCD. For instance, repetitive hand washing can cause skin damage in the end. It is rare for OCD to progress into another mental problem. The most common complication resulting from OCD may include but not limited to:

• Physical/health issues, such as certain skin diseases which result from excessive hand washing
• Unemployment and inability to attend school or any other social activities
• Relationship problems
• Deterioration in quality of life
• Suicidal tendencies and acts

There is no proven single method to prevent obsessive-compulsive disorder. However, preventing OCD from worsening and disrupting life activities can be accomplished by getting treatment as soon as possible.

OCD is a chronic mental disease with periods featured by severe symptoms followed by periods of relatively good improvement. Most people improve with treatment but a completely symptom-free period is improbable to occur. For half or more of children and adolescents cases who present for treatment, the prognosis appears to be good. The likelihood of OCD sufferers to have comorbid (co-existing) major depression and other anxiety disorders is high.

• According to a study published in The Journal of Clinical Psychiatry, the worldwide prevalence of obsessive-compulsive disorder (OCD) is reported to be near to 2% of the general population.
• Results of a survey carried out by a study published in The Journal of Clinical Psychiatry and involved seven countries (United States, Canada, Puerto Rico, Germany, Taiwan, Korea, and New Zealand) confirmed that the OCD annual prevalence rates were consistent among these countries, ranging from 1.1per 100 in Korea and New Zealand to 1.8 per 100 in Puerto Rico. The lowest prevalence rates for all psychiatric disorders reported in Taiwan (0.4 per 100).
• According to a study published in a Scandinavian journal called Acta Psychiatrica Scandinavica, the lifetime prevalence of OCD among Canadian adults measured to be 2.9%.
• According to The National Institute of Mental Health in the United States, the annual prevalence of OCD among adults population is 1.0%, approximately 50.6% of these cases considered sever.
• According to a study published in Mexican journal Salud Mental, prevalence studies of the OCD in Latin American countries are scarce. In Mexico, the prevalence of OCD cases reported as 2.3%, most of them turned out to be females and high comorbidity with depression observed.
• According to a study published in Comprehensive Psychiatry Journal, people with obsessive-compulsive disorder (OCD) have a very low rate of reporting their symptoms to mental health professionals. Only 36.6% of those who included in the study have discussed their symptoms with mental health care provider.
• A study conducted in northern Germany and published in The Journal of Clinical Psychiatry, involved a sample of 4072 persons aged 18–64 years, found that the lifetime prevalence rate of OCD was 0.5% and the twelve-month prevalence rate was 0.39%.
• According to a study published in Psychiatry Research Journal, The estimated annual incidence for OCD in Taiwan reported as 27.57 per 1,000,000 and the one-year prevalence was 65.05 per 1,000,000. Rates of incidence and prevalence show increasing with age, the peak of the findings ranged at age 18–24 years in males and at 35–44 years in females.
• According to an Iranian study published in BMC Psychiatry journal, the rate of OCD in Iran calculated as 1.8% in general population and it is more common in females than males.
• High rates of unemployment among OCD patients and their receipt of disability and welfare payments add a considerable burden to the social cost.
• In many western countries, OCD considered the fourth most common mental illness that may affect all people regardless of their gender, race, age, religion, nationality or socio-economic group.