Obsessive compulsive disorder (OCD) is a mental health condition where a person has obsessive thoughts and compulsive activity.

An obsession is an unwanted and unpleasant thought, image or urge that repeatedly enters a person's mind, causing feelings of anxiety, disgust or unease.

A compulsion is a repetitive behaviour or mental act that someone feels they need to carry out to try to temporarily relieve the unpleasant feelings brought on by the obsessive thought.

For example, someone with a fear of their house being burgled may feel they need to check all the windows and doors are locked several times before they can leave the house.

OCD symptoms can range from mild to severe. Some people with OCD may spend an hour or so a day engaged in obsessive-compulsive thinking and behaviour, but for others the condition can completely take over their life.

Read more about the symptoms of OCD.

What causes OCD?

It's not clear exactly what causes OCD, although a number of factors have been suggested.

In some cases the condition may run in families, and may be linked to certain inherited genes that affect the brain's development.

Brain imaging studies have shown the brains of some people with OCD can be different from the brains of people who do not have the condition.

For example, there may be increased activity in certain areas of the brain, particularly those that deal with strong emotions and the responses to them.

Studies have also shown people with OCD have an imbalance of serotonin in their brain. Serotonin is a chemical the brain uses to transmit information from one brain cell to another.

Read more about the causes of OCD.

Who is affected?

It's estimated around 12 in every 1,000 people in the UK are affected by the condition. This equates to almost 750,000 people.

OCD affects men, women and children. The condition typically first starts to significantly interfere with a person's life during early adulthood, although problems can develop at any age.

Getting help

People with OCD are often reluctant to seek help because they feel ashamed or embarrassed.

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

Seeking help is important because it is unlikely your symptoms will improve if left untreated, and they may get worse.

You should visit your GP if you think you may have OCD. Initially, they will probably ask a number of questions about your symptoms and how they affect you.

If your GP suspects OCD, you may need to be referred to a specialist for an assessment and appropriate treatment.

Read more about diagnosing OCD.

How OCD is treated

With treatment, the outlook for OCD is good. Many people will eventually be cured of their OCD, or their symptoms will at least be reduced enough that they can enjoy a good quality of life.

The main treatments for OCD are:

  • cognitive behavioural therapy (CBT) – involving a therapy known as graded exposure with response prevention (ERP), which encourages you to face your fear and let the obsessive thoughts occur without "neutralising" them with compulsions
  • selective serotonin reuptake inhibitors (SSRIs) – this medication can help reduce your symptoms by altering the balance of chemicals in your brain

If these treatments aren't effective or your condition is particularly severe, you may need to be referred to a specialist mental health service for treatment.

Read more about treating OCD.


Obsessive compulsive disorder (OCD) affects people differently, but usually causes a particular pattern of thought and behaviour.

This pattern has four main steps:

  • obsession – where an unwanted, intrusive and often distressing thought, image or urge repeatedly enters your mind
  • anxiety – the obsession provokes a feeling of intense anxiety or distress
  • compulsion – repetitive behaviours or mental acts that you feel driven to perform as a result of the anxiety and distress caused by the obsession
  • temporary relief – the compulsive behaviour brings temporary relief from anxiety, but the obsession and anxiety soon return, causing the cycle to begin again

Obsessive thoughts

Almost everyone has unpleasant or unwanted thoughts at some point in their life, such as a concern that they may have forgotten to lock the door of the house or that they may contract a disease from touching other people, or even sudden unwelcome violent or offensive mental images.

Most people are able to put these types of thoughts and concerns into context, and they can carry on with their day-to-day life. They do not repeatedly think about worries they know have little substance.

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

Some common obsessions that affect people with OCD include:

  • fear of deliberately harming yourself or others – for example, fear you may attack someone else, even though this type of behaviour disgusts you
  • fear of harming yourself or others by mistake or accident – for example, fear you may set the house on fire by accidentally leaving the cooker on
  • fear of contamination by disease, infection or an unpleasant substance
  • a need for symmetry or orderliness – for example, you may feel the need to ensure all the labels on the tins in your cupboard face the same way

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 who fears becoming contaminated with dirt and germs may wash their hands repeatedly throughout the day, or someone with a fear of causing harm to their family may have the urge to repeat an action multiple times to try to "neutralise" the thought of harm. This latter type of 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 and hand washing
  • checking – such as checking doors are locked, or that the gas or a tap is off
  • counting
  • ordering and arranging
  • hoarding
  • asking for reassurance
  • repeating words silently
  • extensively "overthinking" to ensure the feared consequence of the obsession does not occur – for example, if you fear you may act violently
  • thinking "neutralising" thoughts to counter the obsessive thoughts
  • avoiding places and situations that could trigger obsessive thoughts

Not all compulsive behaviours will be obvious to other people.

Related problems

Some people with OCD may also have or develop other serious mental health problems, including:

  • depression – a condition that typically causes lasting feelings of sadness and hopelessness, or a loss of interest in the things you used to enjoy
  • eating disorders – conditions characterised by an abnormal attitude towards food that cause you to change your eating habits and behaviour
  • generalised anxiety disorder – a condition that causes you to feel anxious about a wide range of situations and issues, rather than one specific event
  • a hoarding disorder – a condition that involves excessively acquiring items and not being able to throw them away, resulting in unmanageable amounts of clutter

People with OCD and severe depression also frequently have suicidal feelings.

Getting help

OCD can stop you carrying out normal day-to-day activities and can have a significant impact on your career, education and social life.

It is therefore important to seek help from your GP if you think you have the condition. With the correct diagnosis and treatment, you should be able to manage your symptoms and have a better quality of life.

You should also visit your GP if you think you may have one of the related mental health problems mentioned above, as these conditions may become more severe if they are left untreated and may make it more difficult for you to cope with your OCD.

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 on 08457 90 90 90. Alternatively, you can call NHS 111.

If you think a friend or family member may have OCD, it's a good idea to talk to them about your concerns and suggest they seek medical advice.

While it might seem natural to try to protect the person with OCD from their own fears, this is counterproductive because it means the problem is not resolved and there is no hope of moving on.

Read more about diagnosing OCD.


Despite much research being carried out into obsessive compulsive disorder (OCD), the exact cause of the condition has not yet been identified.

However, a number of different factors that may play a role in the condition have been suggested. These are described below.


Genetics is thought to play a part in some cases of OCD. Research suggests OCD may be the result of certain inherited genes that affect the development of the brain.

Although no specific genes have been linked to OCD, there is some evidence that suggests a person with OCD is more likely to have another family member with the condition compared with someone who does not have OCD.

However, it is possible there may sometimes be other reasons for this. For example, it has been suggested some people may "learn" OCD as a result of witnessing other family members with the condition.

Brain differences

Brain imaging studies have shown some people with OCD have differences in certain parts of their brain, including increased activity and blood flow, and a lack of the brain chemical serotonin.

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


Serotonin may play a part in OCD. This brain chemical transmits information from one brain cell to another and is known as a neurotransmitter.

Serotonin is responsible for regulating a number of the body's functions, including mood, anxiety, memory and sleep.

It is not known for sure how serotonin contributes to OCD, but some people with the condition appear to have decreased levels of the chemical in their brain.

Medication that increases the levels of serotonin in the brain, such as certain types of antidepressant, have proven effective in treating OCD.

Life events

OCD may be more common in people with a history of having experienced emotional, physical or sexual abuse, neglect, social isolation, teasing or bullying.

An important life event, such as a bereavement, family break-up, a new job, pregnancy or childbirth, may also trigger OCD in people who already have a tendency to develop the condition – for example, because of genetic factors – and may affect the course of the condition.

For example, the death of a loved one may trigger a fear that someone in your family will be harmed.

Stress seems to make the symptoms of OCD worse, but does not cause OCD on its own.


People with certain personality traits may be more likely to have OCD. For example, if you are a neat, meticulous, methodical person with high standards – a "perfectionist" – you may be more likely to develop the condition.

OCD may also be a result of simply being more prone to becoming tense and anxious than most people, or having a very strong sense of responsibility for yourself and others.


It is very important you visit your GP if you have symptoms of obsessive compulsive disorder (OCD).

The impact of OCD on your day-to-day life can be reduced if the condition is diagnosed and effectively treated.

Many people with OCD do not report their symptoms to their GP because they feel ashamed or embarrassed. They may also try to disguise their symptoms from family and friends.

However, if you have OCD, you should not feel ashamed or embarrassed. Like diabetes or asthma, OCD is a long-term health condition, and it is not your fault you have it.

If you think a friend or family member may have OCD, it's a good idea to talk to them carefully about your concerns and suggest they seek medical advice.

Initial questions

Your GP will probably ask you a series of questions to determine whether it's likely you have OCD.

These may be similar to the following:

  • Do you wash or clean a lot?
  • Do you check things a lot?
  • Do you have thoughts that keep 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 upset by mess?
  • Do these problems trouble you?


If the results of the initial screening questions suggest you have OCD, the severity of your symptoms will be assessed either by your GP or a mental health professional.

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

During the assessment, it is important you are open and honest, as accurate and truthful responses will ensure you receive the most appropriate treatment.

OCD is classified into three levels of severity:

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

Healthcare professionals use the term "functional impairment" to refer to the disruption of your daily activities.


Treatment for obsessive compulsive disorder (OCD) depends on the how much the condition is affecting your daily life.

The two main treatments are:

  • cognitive behavioural therapy (CBT) involving graded exposure and response prevention (ERP) – therapy that encourages you to face your fear and let the obsessive thoughts occur without "putting them right" or "neutralising" them with compulsions
  • medication – to control your symptoms by altering the balance of chemicals in your brain

OCD that has a relatively minor impact on your daily life is usually treated with a short course of CBT involving ERP.

If you have OCD that has a more significant impact on your daily life, a more intensive course of CBT with ERP or a type of medication known as selective serotonin reuptake inhibitors (SSRIs) may be recommended instead. You may also be referred to a specialist mental health service.

If your OCD has a severe impact on your daily life, you will usually be referred 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 with experience of treating OCD in children.

The level of treatment for OCD can be increased in steps until it is effective. For example, if a short course of CBT does not help, you may move on to trying SSRIs.

It's important to remember it can take several months before a treatment has a noticeable effect.

Cognitive behavioural therapy with exposure and response prevention

Cognitive behavioural therapy (CBT) that involves exposure and response prevention (ERP) can be used to help people with OCD of all severities.

People with mild to moderate OCD usually need about 10 hours of therapist treatment, combined with exercises done at home between sessions.

Those with moderate to severe OCD may need a more intensive course of CBT that lasts longer than 10 hours.

During the sessions, you will work with your therapist to break down your problems into their separate parts, such as your thoughts, physical feelings and actions.

Your therapist will also need to ask you to use a technique called graded ERP. This therapy encourages you to face your fear and let the obsessive thoughts occur without "putting them right" or neutralising them with compulsions.

It requires motivation and is difficult, but should start with situations that cause you the least anxiety first.

These exposure exercises need to take place several times a day, and need to be done for one to two hours without engaging in compulsions to undo them.

Although this sounds frightening, people with OCD find that when they confront their anxiety without carrying out their compulsion, the anxiety does eventually improve or go away. Each time, the anxiety is likely to be less and last for a shorter period of time.

Once you have conquered one exposure task, you can move on to a more difficult task, until you have overcome all of the situations that make you anxious. 


You may need medication if CBT fails to treat mild OCD or if you have moderate or severe OCD. The main type of medication you may be prescribed is discussed below.

If these medications prove ineffective, you will be referred to a specialist mental health service.

Selective serotonin reuptake inhibitors

Selective serotonin reuptake inhibitors (SSRIs) are a type of antidepressant medication that increase the levels of a chemical called serotonin in your brain. Serotonin is a neurotransmitter the brain uses to transmit information from one brain cell to another.

Although SSRIs are a type of antidepressant, they have been shown to work in people with OCD regardless of their level of depression. The doses that have been shown to be effective in OCD are also higher than those generally used for depression.

Possible SSRIs you may be prescribed include:

  • citalopram
  • escitalopram
  • fluoxetine
  • fluvoxamine
  • paroxetine
  • sertraline

You will usually need to take an SSRI for 12 weeks before you notice any benefit. Most people with moderate to severe OCD need to take one for at least 12 months.

After this time, your condition will be reviewed. If it causes few or no troublesome symptoms, you may be able to stop taking the medication.

People with more severe OCD, however, may need to take the medication for many years to prevent the condition recurring.

Possible side effects of SSRIs can include headaches, feeling agitated or shaky, and feeling sick. However, these will often pass within a few weeks.

SSRIs can also affect your heart, so it is advisable to have an electrocardiogram (ECG) after being on the medication for a few weeks. An ECG is a simple test to measure the electrical activity of your heart.

There is also an extremely small chance that SSRIs will increase your anxiety, which can very occasionally cause you to have suicidal thoughts or a desire to self-harm.

Contact your GP immediately or go to your nearest accident and emergency (A&E) department if you are taking an SSRI and have suicidal thoughts or want to self-harm.

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

To find out more about the possible side effects, check the patient information leaflet that comes with your medicine.

Further treatment

Further specialist treatment may sometimes be necessary if you have tried all the treatments above and your OCD is still not under control.

Some people with severe, long-term, difficult-to-treat (refractory) OCD may be referred to the National Service for Refractory OCD centre.

The service offers assessment and treatment to people with OCD who have not responded to treatments available from their local and regional OCD specialist services.

To be eligible for this service, you must have been diagnosed as having severe OCD and have received:

  • at least two full trials of different SSRIs at recommended doses
  • two trials of unsuccessful CBT treatments both in a clinic and at home
  • additional treatment with a dopamine-blocking agent medication or an SSRI at a dose higher than normally recommended

Most people improve after receiving treatment from the national service.

Last updated:
03 May 2023