Obsessive Compulsive Disorder (OCD) – A Guide

Focus on Disability - For Disabled People, the Elderly and their Carers in the UK

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

Symptoms of obsessive compulsive disorder
Causes of obsessive compulsive disorder
Diagnosing obsessive compulsive disorder
Treating obsessive compulsive disorder



An obsession is defined as an unwanted thought, image or urge that repeatedly enters a person’s mind.


A compulsion is defined as a repetitive behaviour or mental act that a person feels compelled to perform.

Unlike some other types of compulsive behaviour, such as an addiction to drugs or gambling, a person with OCD gets no pleasure from their compulsive behaviour. They feel that they need to carry out their compulsion to prevent their obsession becoming true. For example, a person who is obsessed with the fear that they will catch a serious disease may feel compelled to have a shower every time they use a public toilet

How common is OCD?

OCD is one of the most common mental health conditions. It is estimated that about 1-3% of adults and 2% of children and teenagers have OCD.

In men, OCD symptoms usually begin during adolescence. In women they generally start later, usually in the early 20s.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 around one hour a day engaged in obsessive compulsive thinking and behaviour, while for others, the symptoms completely dominate their life.

The causes of OCD are unknown.


If left untreated, the symptoms of OCD may not improve and, in some cases, they will get worse.

With treatment, the prognosis for OCD is good, and some people will achieve a complete cure. Even if a complete cure is not achievable, treatmentcan reduce the severity of a person’s symptoms and help them to achieve a good quality of life.

A form of psychotherapy, known as cognitive behavioural therapy (CBT), can be very successful in helping many people with OCD.

Symptoms of obsessive compulsive disorder

Patterns of thought and behaviour

Most people with obsessive compulsive disorder (OCD) generally fall into a set pattern or cycle of thought and behaviour. This pattern has four main steps which are described below.

  • Obsession:your mind becomes 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 in order 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.
  • Temporarily relief: the compulsive behaviour brings temporary relief from anxiety, but the obsession and anxiety soon returns, meaning that the pattern or cycle begins again.

Obsessive thoughts

Almost all people have unwanted and unpleasant thoughts, such as a nagging worry that their job may not be secure, or a brief suspicion that a partner may have been unfaithful. Most people can usually put these type of thoughts and concerns into context and are able to carry on with their day-to-day lives.

However, if you experience 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 are listed below.

  • Fear of being harmed.
  • Fear of causing harm to others.
  • Fear of contamination by disease, infection, or other unpleasant substance
  • A need for symmetry, or orderliness. For example, someone with OCD may feel the need to ensure that all the labels on the tins in their cupboard face the same way.
  • Fear of committing an aggressive, or unpleasant, act.
  • Fear that you will commit an act that would seriously offend your religious beliefs.
  • Fear that other people will consider you to be a sexual deviant.
  • Fear that you will make a mistake that has serious consequences. For example, your house willburn down because you left the gas on, or all your possessions will be stolen because you forgot to lock your door.

Compulsive behaviour

Most compulsions arise from the initial obsession. In some cases, the type of compulsive behaviour is in some way logically connected to the obsession, such as repeated hand washing in order to prevent disease.

However, in many cases of OCD, the compulsion has no logical connection to the obsession. Instead, it is a type of ‘magical’ or superstitious behaviour that the person believes has the power to prevent the object of their obsession from occurring.

For example, a person with OCD may feel compelled to count every red car that they see on the road because they believe that doing so will prevent their mother from dying in a car crash.

This type of ‘magical’, compulsive behaviour is particularly common in children with OCD.

Although most people with OCD realise that such compulsive behaviour is irrational and makes no logical sense, they’re unable to stop acting on their compulsion.

Some common types of compulsive behaviour found in people with OCD include:

  • Checking that doors are locked, and that gas taps and light switches are turned off.
  • Cleaning and washing.
  • Repeating certain acts or rituals such as having to touch every second lamp post while walking down the street.
  • Constantly repeating certain words or phrases in your mind.
  • Hoarding or collecting objects that usually have no value, such as supermarket bags and junk mail.
  • Counting.

Causes of obsessive compulsive disorder

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

Biological factors

There is evidence to suggest that OCD may be the result of certain inherited genes that affect the development of the brain.

No specific genes have been linked to OCD, but there is some limited 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 than somebody who does not have OCD.

The basal ganglia

Brain imaging studies have shown that people with OCD have abnormalities in a part of the brain known as the basal ganglia (a group of nerves).

In evolutionary terms, the basal ganglia is very old, and is thought to be responsible for some of the most primitive and powerful emotions. For example, our fight or flight reflex, which is an animal’s ability to recognise a potential threat and then decide whether to attack or run away.

One theory is that OCD develops as a result of a malfunction of the basal ganglia, which leads to a person with the condition believing that they are under threat. Their conscious mind knows that the threat is not real, but the subconscious, emotional power of the basal ganglia preventsthe conscious mind from shaking off the anxiety and fear. As a result, the brain adopts compulsive behaviour as a kind of coping strategy.


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 levels of serotonin in the brain, such as certain anti-depressants, have proven successful in helping to treat the symptoms of OCD.

Adverse life events

There is some evidence that an adverse life event, such as a bereavement or family break-up, may trigger the onset of OCD in people who have a pre-existing biological or psychological predisposition (tendency) to OCD.

Diagnosing obsessive compulsive disorder

The importance of 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. It is also not unusual for a person with OCD to go to great lengths to disguise their symptoms from friends or family.

However, if you have OCD it is important to remember that there is nothing to feel ashamed or embarrassed about. Like diabetes or asthma, OCD is a chronic health condition, and it is not your fault that you have developed it.

Getting help for others

Sometimes, the friends and relatives of a person with OCD find themselves ‘playing along’ with their strange behaviourin ordernot to upset them. 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.

Initial screening

When visiting your GP, he or she will probablyask you a series of questions that, in the past, have been successful in assessing whether or not people have OCD. These questions may include those listed below.

  • Do you wash and 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 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, but they all ask you a series of detailed questions in order to determine 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 honest because accurate and truthful responses will ensure that you receive the most appropriate type of 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. Health professionals refer to this disruption of daily function as functional impairment. The different severities of OCD are classified as follows:

  • Mild functional impairment: obsessive thinking and compulsive behaviour occupy one hour of your day.
  • Moderate functional impairment: obsessive thinking and compulsive behaviour occupy two hours of your day.
  • Severe functional impairments: obsessive thinking and compulsive behaviour occupy more than three hours of your day.

Treating obsessive compulsive disorder

Treatment plan

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

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

OCD that causes moderate functional impairment can be treated with a more intensive course of CBT, or the type of 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 health professional with experience in treating OCD in children.

Psychological treatments for OCD

CBT is the the most widely used psychological treatment for OCD. It is based on the idea that most unwanted thinking patterns, beliefs, and emotional and behavioural reactions are learnt over a long period of time.

The aim of CBT is to identify the thinking patterns that are causing you to have unwanted feelings and behaviour, and to learn to replace this thinking with more realistic and useful thoughts and beliefs.

Exposure and response prevention

A particular type of CBT called exposure and response prevention (ERP) hassuccessfully achieved this aim. ERP involves ‘exposing’ yourself to situations or objects that are currently causing you fear and anxiety. Exposure can be:

  • Actual, such as handling dirty plates or using a public toilet.
  • Mental, such as mentally picturing yourself forgetting to lock your door or leaving the oven on.

Once exposure has taken place, most people with OCD will feel the need to engage in compulsive behaviour in order to reduce the anxiety that the exposure has caused them. However, the CBT therapist will work with you in order to prevent, or at least delay, this compulsive response.

Over time, the exposure to an unpleasant object or situation will cause less anxiety and the need for a compulsive response will become weaker.

To begin with, your therapist will set targets for exposure that are relatively easy to cope with before moving on to targets that are currently causing you considerable anxiety.

People with mild to moderate OCD will usually require about 10 one-hour sessions with a CBT counsellor. Those with moderate to severe OCD may require a more intensive course of CBT lasting more than 10 hours.

Medication for OCD

Selective serotonin reuptake inhibitors (SSRIs)

SSRIs are a type of antidepressant that are usually recommended for people with moderate to severe OCD.

You will normally need to take a SSRI for 12 weeks before you begin to notice any benefit.

Side effects of SSRIs include:

  • Headache.
  • Nausea.

These side effects should pass within a few weeks.

There is a small chance that SSRIs will increase your feelings of anxiety, which may lead to you experiencing related suicidal thoughts and the desire to self-harm.

Contact your GP immediately if you are taking a SSRI and you experience suicidal thoughts or the desire to self-harm.

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 no, or very few, troublesome symptoms, you may be able to stop taking SSRIs.


Clomipramine is a tricyclic antidepressant (TCA) that can be used as an alternative to SSRIs for the treatment of OCD. TCAs are not as commonly used as SSRIs because they cause more side effects. They can be effective in treating people with OCD who are unable or unwilling to take SSRIs.

Side effects of clomipramine include:

  • Dry mouth.
  • Constipation.
  • Headache.
  • Dizziness.
  • Fatigue.
  • Increased sweating.

Clomipramine is not suitable for people with low blood pressure (hypotension) or heart disease. Therefore, if you are at risk of either of these two conditions, your GP may recommend a blood pressure test and an electrocardiogram (ECG) before you begin your treatment.

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

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. These groups can provide reassurance, help toreduce any feelings of isolation, and give you a chance to socialise with other people.

Support groups can also provide advice and information to family members and friends who may be affected by your OCD.

See Useful links for more information about support groups.


Surgery for obsessive compulsive disorder is usually considered to be a last-resort treatment for severe OCD when all other forms of treatment have failed. Most surgeons would only consider a person suitable for surgery if they have spent at least five years trying other forms of treatment, such as CBT, without success.

During surgery, 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.

By burning away a small part of the limbic system, the surgeon is often able to ‘re-wire’ the brain and fully, or at least partially, resolve chronic mental health conditions such as OCD.

However, surgery is not a guaranteed cure for OCD. Information collected by the Royal College of Psychiatrists (RCP) found that out of 478 cases of surgery for OCD:

  • 54% resulted in a marked improvement.
  • 27% resulted in a lesser improvement.
  • 14% made no difference.
  • 1% made the symptoms worse.

Surgery for OCD carries the risks of both short- and long-term side effects.

Short-term side effects include:

  • Headaches.
  • Mental confusion.
  • Memory loss.
  • Poor concentration.
  • Seizures.

These short-term side effects should resolve about a month after surgery.

Long-term side effects include:

  • Weight gain.
  • Apathy (a lack of interest).

Long-term side effects may last for up to 12 months.



Some people with obsessive compulsive disorder (OCD) also develop depression.

Do not ignore any feelings of depression,because if they’re 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. The helpline number is:

Alternatively, call NHS 111.