Obsessive compulsive disorder

Page last reviewed: 13/07/2011

Obsessive compulsive disorder (OCD) is a chronic (long-term) mental health condition that is usually associated with obsessive thoughts and compulsive behaviour.

Obsessions and compulsions

An obsession is an unwanted, unpleasant thought, image or urge that repeatedly enters a person's mind and results in anxiety. A compulsion is a repetitive behaviour or mental act that a person feels compelled to perform to try to avert or undo the effect of the obsession.

Unlike the normal use of the word 'obsession', which may describe something that an individual enjoys, the obsession in OCD is unpleasant and frightening. The person feels the need to carry out their compulsion in order to prevent their obsession becoming true. For example, someone who is obsessively scared that they will catch a disease may feel compelled to have a shower every time they use a toilet.

How common is OCD?

OCD is one of the most common mental health conditions. It is estimated that up to 3 in 100 adults and up to 5 in 100 children and teenagers have OCD.

OCD usually starts in early adult life, with men tending to report earlier symptoms than women. However, OCD symptoms can begin at any time, including childhood.

The symptoms of OCD can range from mild to severe. For example, some people with OCD will spend about an hour a day engaged in obsessive compulsive thinking and behaviour. For others, the condition can completely take over their life.

The causes of OCD are unknown, although there are several theories. For more information, see OCD - causes. 


If you have OCD, seeking help is the most important thing you can do. Left untreated, the symptoms of OCD may not improve. In some cases they will get worse. Without treatment, nearly half of people with OCD still have symptoms 30 years later.

With treatment, the outlook for OCD is good. Some people will achieve a complete cure. Even if a complete cure is not achievable, treatment can reduce the severity of your symptoms and help you to achieve a good quality of life.

A form of psychotherapy, known as cognitive behavioural therapy, which includes graded exposure and response prevention, is a proven treatment with a high rate of success in OCD. This may also be combined with medication, such as antidepressants.

About 80% of people with OCD will respond to initial treatment. See OCD - treatment for more information.

Page last reviewed: 13/07/2011

While obsessive compulsive disorder (OCD) is a condition that can affect people differently, it usually causes a particular pattern of thought and behaviour.

Patterns of thought and behaviour

Most people with OCD generally fall into a set pattern or cycle of thought and behaviour. This pattern has four main steps:

  • Obsession - your mind is overwhelmed by a constant obsessive fear or concern, such as the fear that your house will be burgled.
  • Anxiety - this obsession provokes a feeling of intense anxiety and distress.
  • Compulsion - you then adopt a pattern of compulsive behaviour to reduce your anxiety and distress, such as checking that all your windows and doors are locked at least three times before leaving your house.
  • Temporary relief - the compulsive behaviour brings temporary relief from anxiety, but the obsession and anxiety soon return, causing the pattern or cycle to begin again.

Obsessive thoughts

Almost everyone has unwanted and unpleasant thoughts, such as a nagging worry that their job may not be secure, or a brief suspicion that a partner has been unfaithful. Most people can put these types of thoughts and concerns into context and are able to carry on with their day-to-day lives; they do not repeatedly think about worries that they realise have little substance.

However, if you have a persistent, unwanted and unpleasant thought that dominates your thinking to the extent that it interrupts your other thoughts, you may have developed an obsession.

Some common obsessions that affect people with OCD include:

  • fear of causing harm to yourself or to others through a deliberate action - for example, fear that you may attack someone else even though this type of behaviour disgusts you
  • fear of causing harm to yourself or to others through a mistake or accident - for example, fear that you may set the house on fire by accidently leaving the cooker on, which leads you to repeatedly check the kitchen appliances
  • fear of contamination by disease, infection or other unpleasant substance
  • a need for symmetry or orderliness - e.g. you may feel the need to ensure that all the labels on the tins in your cupboard face the same way
  • fear of committing an act that would seriously offend your religious beliefs

Compulsive behaviour

Compulsions arise as a way of trying to reduce or prevent the harm of the obsessive thought. However, this behaviour is either excessive or not realistically connected at all. For example, a person with a fear of contamination by dirt and germs may wash their hands 50 times a day, or someone with a fear of causing harm to their family by thinking of disasters may have the urge to repeat an action multiple times to try and 'neutralise' the thought of harm. This latter type of 'magical', compulsive behaviour is particularly common in children with OCD.

Most people with OCD realise that such compulsive behaviour is irrational and makes no logical sense, but they cannot stop acting on their compulsion.

Some common types of compulsive behaviour that affect people with OCD include:

  • cleaning
  • handwashing
  • checking - such as checking that doors are locked, or that the gas or a tap is off 
  • counting
  • ordering and arranging
  • hoarding 
  • asking for reassurance
  • needing to confess
  • repeating words silently
  • prolonged thoughts about the same subject
  • 'neutralising' thoughts (to counter the obsessional thoughts or images)

Page last reviewed: 13/07/2011

The exact cause of obsessive compulsive disorder (OCD) is unknown, but a number of theories have been suggested. These are explained below.

Genetic factors

There is evidence to suggest that OCD may be the result of certain inherited genes (units of genetic material) that affect the development of the brain.

No specific genes have been linked to OCD, but there is some evidence that the condition runs in families. For example, a person with OCD is four times more likely to have another family member with the condition compared with someone who does not have OCD.

Genetic and family studies have also shown that OCD may be related to other conditions, such as:

  • tics - rapid, repeated, involuntary contractions of a group of muscles
  • Tourette's syndrome - a condition that causes a person to make repetitive movements or sounds

Some people with OCD may also have tics or Tourette's syndrome.

Brain abnormalities

Brain imaging studies have shown that people with OCD have abnormalities in some parts of their brain, such as increased blood flow and activity.

The affected areas of the brain deal with strong emotions and the response to those emotions. In the studies, after successful treatment with cognitive behavioural therapy or selective serotonin reuptake inhibitors (SSRIs), the activity in the brain returned to normal.


The chemical serotonin also seems to play a part in OCD. Serotonin is a neurotransmitter, a chemical that the brain uses to transmit information from one brain cell to another.

Exactly how serotonin contributes to OCD is unknown, but medication that increases the serotonin levels in the brain, such as certain antidepressants, have successfully helped to treat the symptoms of OCD.


There have been reports of some children and young people developing OCD after an infection caused by streptococcal bacteria. It is possible that the antibodies (infection-fighting proteins) produced by the body react with part of the brain and cause OCD.

Life events

An adverse life event, such as a bereavement or family break-up, may trigger OCD in people who already have a tendency to the condition - for example, due to genetic factors.

This life event could also affect the course of your condition. For example, the death of a loved one may trigger a fear that someone in your family will be harmed. Stress, which can also be caused by life events, seems to make OCD symptoms worse. However, stress on its own is not a cause of the condition.

Family involvement

Your upbringing is not thought to cause OCD. However, some factors could make OCD more likely to develop. For example, having parents who are very overprotective. 

It is unhelpful if the family of someone with OCD becomes involved. For example, someone with OCD may ask a family member for constant reassurance about one of their fears, such as whether they have locked the door. If the family member continually reassures them that they did, in order to make them feel better, it may prevent them seeking necessary treatment.

Antibodies are proteins that are produced by the body to neutralise or destroy disease-carrying organisms and toxins.
A gene is a unit of genetic material that determines your body's characteristics.
Genetic is a term that refers to genes.

Page last reviewed: 13/07/2011

Seeking treatment

Many people with obsessive compulsive disorder (OCD) are reluctant to report their symptoms to a GP because they feel ashamed and embarrassed about their condition. People with OCD sometimes make a great effort to disguise their symptoms from their family and friends.

However, if you have OCD there is nothing to feel ashamed or embarrassed about. Like diabetes or asthma, OCD is a chronic (long-term) health condition. It is not your fault that you have it.

Getting help for others

Sometimes, the friends and relatives of a person with OCD 'play along' with their strange behaviour to avoid upsetting them. However, this is not recommended because it can reinforce the person's obsessive compulsive behaviour.

It is better to confront them with the reality of their unusual behaviour, and suggest that they seek medical advice. See OCD - supporting someone with OCD for more information.

Initial screening

When you visit your GP, they will probably ask you a series of questions.

The questions, which form the Fineberg-Zohar screening questionnaire, are a way of determining whether you are likely to have OCD. But, like all screening questionnaires, many people without OCD may score positively on the questionnaire.

The questions may include those listed below.

  • Do you wash or clean a lot?
  • Do you check things a lot?
  • Is there any thought that keeps bothering you that you would like to get rid of but cannot?
  • Do your daily activities take a long time to finish?
  • Are you concerned about putting things in a special order or are you very upset by mess?
  • Do these problems trouble you?


If the results of the initial screening questions suggest that you have OCD, the severity of your symptoms will need to be assessed. Assessment may be carried out by your GP or you may be referred to a mental health professional.

There are several different methods of assessment. All of them involve asking a series of detailed questions to find out how much of your day-to-day life is affected by obsessive-compulsive thoughts and behaviour.

During the assessment process, it is important for you to be open and honest because accurate and truthful responses will ensure that you get the most appropriate treatment.

Types of OCD

The severity of OCD can be determined by how much your symptoms affect your ability to function normally on a day-to-day basis. Healthcare professionals refer to the disruption of daily function as functional impairment. OCD is classified into three levels of severity:

  • mild functional impairment - obsessive thinking and compulsive behaviour occupy less than one hour of your day
  • moderate functional impairment - obsessive thinking and compulsive behaviour occupy one to three hours of your day
  • severe functional impairment - obsessive thinking and compulsive behaviour occupy more than three hours of your day

Page last reviewed: 13/07/2011

If you have obsessive compulsive disorder (OCD), your recommended treatment plan will depend on how much your OCD is affecting your ability to function. Treatment is likely to involve:

  • behavioural therapy - to change the way you behave and reduce your anxiety 
  • medication - to control your symptoms 

Treatment plan

OCD that causes mild functional impairment is usually treated using a short course of cognitive behavioural therapy (CBT).

OCD that causes moderate functional impairment can be treated with a more intensive course of CBT, or antidepressants known as selective seretonin reuptake inhibitors (SSRIs). Such cases may also require referral to a specialist mental health service.

OCD that causes severe functional impairment will require referral to a specialist mental health service for a combination of intensive CBT and a course of SSRIs.

Children with OCD are usually referred to a healthcare professional who has experience of treating OCD in children.

Behavioural therapy 

Cognitive behavioural therapy involving graded exposure and response prevention has repeatedly proved to be an effective treatment for OCD.

Exposure and response prevention

Exposure and response prevention (ERP) is a treatment that involves identifying a number of situations that cause you anxiety. These are then placed in order, depending on which situation causes the most anxiety.

You and your therapist will identify tasks that will expose you to the situation that cause anxiety, but at a level that you can cope with. You need to do the exposure tasks without carrying out your anxiety-relieving compulsions (the actions you usually take to help you cope with the situation).

Although this sounds frightening, people with OCD find that when they confront their anxiety without their compulsion, the anxiety disappears completely in one to two hours.

This same exposure task should be repeated two or three times a day. Each time, the anxiety is likely to be less, and last for a shorter period of time. Once one step has been conquered you can move onto a more difficult exposure task until you have overcome all of the situations that make you anxious. 

People with mild to moderate OCD usually need about 10 hours of therapist treatment combined with self-treatment exposure exercises between sessions. Those with moderate to severe OCD may need a more intensive course of CBT that lasts for more than 10 hours.


You may be prescribed medication if CBT fails to treat mild OCD or if you have moderate or severe OCD. The different types of medication that you may be prescribed are discussed below.

Selective serotonin reuptake inhibitors (SSRIs)

Selective serotonin reuptake inhibitors (SSRIs) are a type of antidepressant that boost levels of a substance called serotonin in the brain. Serotonin is a neurotransmitter, which is a chemical that the brain uses to transmit information from one brain cell to another. See the Health A-Z topic about SSRIs for more information about this type of medication.

Possible SSRIs that you may be prescribed include: 

  • fluoxetine
  • fluvoxamine
  • paroxetine
  • sertaline
  • citalopram
  • escitalopram

You normally need to take an SSRI for 12 weeks before you notice any benefit. Most people with moderate to severe OCD are required to take SSRIs for at least 12 months. After that time, your condition will be reviewed. If the condition is causing you very few or no troublesome symptoms, you may be able to stop taking SSRIs.

Side effects of SSRIs include:

  • headaches
  • feeling sick

These side effects should pass within a few weeks.

There is a small chance that SSRIs will increase your anxiety, which may cause you to have suicidal thoughts or a desire to self-harm.

Contact your GP immediately or go to your nearest hospital if you are taking an SSRI and you have suicidal thoughts or want to self-harm.

It may be helpful to tell a close friend or relative that you are taking SSRIs. Ask them to tell you if they notice changes in your behaviour or if they are worried about the way you are acting.

You may also have side effects when you stop taking SSRIs, so do not suddenly stop taking your medicine. If you no longer need the medicine, your GP will gradually reduce your dose. 

See the patient information leaflet of your medicine to find out more about the possible side effects. Or see the Medicines information tab above.

Some people respond better to one SSRI rather than another. If you have been taking full recommended doses of an SSRI for three months without benefit, you may be prescribed a different type of SSRI.

The doses of SSRI recommended for OCD are higher than those generally used for depression. There is evidence that low doses of SSRIs are ineffective.


Clomipramine is a tricyclic antidepressant (TCA), which can be used as an alternative to SSRIs for treating OCD. TCAs are not as commonly used as SSRIs because they cause more side effects. However, they can be effective in treating people with OCD who cannot tolerate SSRIs.

Side effects of clomipramine include:

  • a dry mouth
  • constipation
  • diarrhoea
  • blurred vision
  • dizziness
  • fatigue (extreme tiredness)

Clomipramine is not suitable for people who have:

  • low blood pressure
  • arrhythmia (an irregular heartbeat)
  • recently had a heart attack

For adults at risk of cardiovascular disease (conditions that affect the heart or blood vessels), your GP may recommend a blood pressure test and an electrocardiogram (ECG) before starting your treatment. An electrocardiograph (ECG) measures the electrical activity of your heart.

As with SSRIs, a 12-month course of clomipramine is usually recommended, after which time your symptoms will be reviewed.

See the patient information leaflet that comes with your medicine to find out more about the possible side effects. Or see the Clomipramine medicines information above.

If SSRIs or clomipramine prove to be ineffective, you will be referred to a specialist mental health service.

Support groups

Many people with OCD find support groups helpful. Support groups can:

  • reassure you 
  • reduce any feelings of isolation
  • give you a chance to socialise with others

Support groups can also provide information and advice for family members and friends who may be affected by your OCD. OCD Ireland can give you information on groups in your area. You can find information on their website at the link below.


Surgery for OCD is the very last resort for treating severe OCD when all other forms of treatment have failed. It should not be considered at all until someone has:

  • received at least two full trials of different SSRIs or clomipramine, at recommended doses
  • had treatment for refractory OCD (OCD that does not respond to treatment) with the addition of antipsychotic medication or the recommended higher doses of SSRIs or mood stabilisers
  • received unsuccessful CBT treatments both in a clinic and at home, as well as having been treated by the National Service for OCD (see below)

Ablation neurosurgery

A very small number of people with OCD will need neurosurgery. During ablation neurosurgery, a neurosurgeon (a surgeon who specialises in surgery involving the brain and nervous system) will use an electric current or a pulse of radiation to burn away a small part of the limbic system. The limbic system is a structure in the brain that is responsible for some of the most important brain functions, such as the higher emotions, memory and behaviour.

Neurosurgery has never been subjected to controlled clinical trials. However, a survey conducted by the Royal College of Psychiatrists found that out of 478 people who had surgery for OCD, more than half felt that they had improved. But as many as 15% felt unchanged or worse.

In addition, surgery for OCD carries the risks of both short- and long-term side effects, such as memory loss and mental confusion, which can be serious and irreversible.

Deep brain stimulation

Deep brain stimulation is an alternative surgical technique that may be used more frequently to treat OCD in the future. Currently, it is only used as part of medical research.

Deep brain stimulation involves implanting an electrical generator into your chest and electrodes (small metal discs) into your brain. An electrical signal is sent from the device in your chest to the electrodes in your brain.

Some small studies looking at deep brain stimulation have reported an improvement in symptoms. But some possible serious side effects are associated with the technique, including:

  • infection 
  • bleeding inside the brain

Possible treatment plan

If your treatment does not appear to be successful, there are other options. The level of treatment you are receiving can increase in steps until it is effective. You should also remember that treatments can take several months before they have a noticeable effect.

Below is an example of the treatment steps that may be followed if you have OCD.

  • You are likely to start with a course of CBT. Different types of CBT and longer sessions can be used if your initial course of CBT does not work.
  • You may then be prescribed a SSRI.
  • If your SSRI is not effective, your dose may be increased.
  • If this does not work, there are several different SSRIs that you can try.
  • If this still proves to be ineffective, you may be prescribed higher doses of SSRIs or you may be given another medication to take with your SSRI. One of the most common additional types of medication is antipsychotic medicine. Antipsychotics are used to treat a number of different mental health conditions.
  • CBT delivered by a highly specialised team can also be used with any type of medication that you are taking. 

Page last reviewed: 13/07/2011


Some people who have obsessive compulsive disorder (OCD) also develop depression (feelings of extreme sadness that last a long time).

You should not ignore feelings of depression. If they are not treated they can become more severe. Untreated depression will also make it harder for you to cope with the symptoms of OCD.

If you have been feeling very down during the past month and you no longer take pleasure in the things that you used to enjoy, you may be experiencing depression. If this is the case, you should contact your GP.

People with OCD and severe depression may sometimes have suicidal feelings.

Contact your GP or care team immediately if you are depressed and feeling suicidal. You can also telephone the Samaritans to talk in confidence to a counsellor at 1850 60 90 90

Quality of life

OCD can prevent you from doing normal day-do-day activities, which can then have an impact on your career or studies. This will affect your quality of life and could also affect your income if, for example, you are unable to work.

Therefore, it is very important to seek help. With the correct diagnosis and treatment, you should be able to manage your condition and improve your quality of life.

Page last reviewed: 13/07/2011

Many people with OCD can trace some of their anxieties and compulsions back to their childhood. On average, the compulsions start to interfere significantly with their lives between the ages of 17 and 20. However, it can be as early as five years old or as late as 70 years old.

The unwelcome and obsessive fears that threaten to become overwhelming as the condition develops vary from person to person. So too does the compulsive behaviour that the person uses to try and control the fears.

How much impact OCD has on a person's life depends on:

  • the amount of time spent on a compulsive behaviour or ritual
  • the intensity of the behaviour
  • how much of it happens in their mind rather than in their actions

Rituals that involve checking can affect different people in different ways. For example, when leaving the house, a person with OCD might shut the door behind them, then think about it again and again for much of the day. Their worry about the door being properly locked is constant, and so is the misery and depression that goes with it. Despite this, some people with OCD can hold down demanding jobs.

For others, the behaviour can take up all of their focus. When they try to leave the house they get stuck in the hallway, repeatedly checking the lock. In the most extreme cases, the anxiety and the thought of doing these rituals can prevent a person from moving for hours.

Supporting family members with OCD

Naturally, the family members of someone who is openly affected by these behaviours will want to help. For a person who has not had mental health training and is unaware of the treatment options, this usually means trying to share the load. For instance, they may take on some of the rituals of a compulsive cleaner or checker.

This might seem the natural thing to do, but the whole family may end up constantly trying to protect the person with OCD from their own fears. This is counterproductive. The problem is not sorted out, and there is no hope of moving on. In this way, the whole family 'suffers from OCD'.

The best response is to help the person with OCD to seek treatment and to support them as they change and recover. Once therapy has begun, the contribution and support of a partner is invaluable.

Sometimes, the person with OCD can feel embarrassed or ashamed and will try to hide their rituals from others. When this involves a physical activity, such as hand washing, the first sign that something is wrong may be the appearance of their hands or the long amount of time they spend in the bathroom. Mental rituals can be harder to notice.

Fortunately, when someone with OCD decides to get help, a good GP will be able to recognise the signs and get further support from specialists.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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