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Obsessive-compulsive disorder (OCD)

Explains obsessive-compulsive disorder (OCD), including possible causes and how you can access treatment and support. Includes tips for helping yourself, and guidance for friends and family.

What are obsessions?

Obsessions are persistent thoughts, pictures, urges or doubts that appear in your mind again and again. They interrupt your thoughts against your control, and can be really frightening, graphic and disturbing. They may make you feel anxious, disgusted or uncomfortable.

You might feel you can't share them with others or that there is something wrong with you that you have to hide. You might feel upset that you are capable of having such thoughts.

Remember: obsessions are not a reflection of your personality. People with OCD are very unlikely to act on their thoughts.

"I get unwanted thoughts all through the day, which is very distressing and affects my ability to interact with others and concentrate on my studies."

Types and examples of obsessions

  • Worrying you've already harmed someone by not being careful enough. For example, that you have knocked someone over in your car.
  • Worrying you're going to harm someone because you will lose control. For example, that you will push someone in front of a train or stab them.
  • Violent intrusive thoughts or images of yourself doing something violent or abusive. These thoughts might make you worry that you are a dangerous person.
  • Relationship intrusive thoughts often appear as doubts about whether a relationship is right or whether you or your partner's feelings are strong enough. They might lead you to end your relationship to get rid of the doubt and anxiety.
  • Sexual intrusive thoughts or images. These could be related to children, family members or to sexually aggressive behaviour. You might worry that you could be a paedophile or a rapist, or that you are sexually attracted to someone in your family.
  • Contamination (for example by dirt, germs or faeces). You might worry that you have been contaminated and that you - or other people - are spreading the contamination. You might worry that you have or might get a disease.
  • Mental contamination. You might experience feelings of dirtiness that are triggered by a person who has harmed you in some way. These feelings may also be triggered by your own thoughts, images or memories.
  • You might have a fear that something bad will happen if everything isn't 'right'. For example if things are not clean, in order or symmetrical.

You might experience more than one type of obsession. They are often linked together. For example you might experience a fear of contamination and a fear of doing someone harm by accidentally making them ill.

You can read more about the different types of obsessions read more about different types of obsession on the OCD-UK website.

Anxiety and arousal

Intrusive sexual thoughts may lead you to constantly monitor and check your genitals. This attention and the anxiety you are feeling may actually increase blood flow and physical arousal. This can make you feel as if you are aroused by the intrusive thoughts when in fact the opposite is true. Many people with this type of OCD call this 'groinal response'.

"I would seek medical reassurance online and for a day or so I could breathe a sigh of relief... but then the doubt would set in and I started the process again."

What are compulsions?

Compulsions are repetitive activities that you feel you have to do. The aim of a compulsion is to try and deal with the distress caused by obsessive thoughts.

You might have to continue doing the compulsion until the anxiety goes away and things feel right again. You might know that it doesn't make sense to carry out a compulsion - but it can still feel too scary not to.

Repeating compulsions is often very time-consuming and the relief they give you doesn't usually last very long.

Compulsions can:

  • be physical actions
  • be mental rituals (people who only have mental compulsions sometimes refer to their OCD as Pure O)
  • involve a number (for example, you might feel you have to complete a compulsion a specific number of times without interruption).

Types and examples of compulsions


  • washing your hands, body or things around you a lot
  • touching things in a particular order or at a certain time
  • arranging objects in a particular way


  • checking doors and windows to make sure they are locked
  • checking your body or clothes for contamination
  • checking your body to see how it responds to intrusive thoughts
  • checking your memory to make sure an intrusive thought didn't actually happen
  • checking your route to work to make sure you didn't cause an accident

Correcting thoughts

  • repeating a word, name or phrase in your head or out loud
  • counting to a certain number
  • replacing an intrusive thought with a different image


  • repeatedly asking other people to tell you that everything is alright.

What is 'Pure O'?

Pure O stands for 'purely obsessional'. People sometimes use this phrase to describe a type of OCD where they experience distressing intrusive thoughts but there are no external signs of compulsions (for example checking or washing). The name is slightly misleading as it suggests that there are no compulsions at all.

If you have Pure O you will still experience mental compulsions but you might not be aware of them. Because they are not as obvious as physical compulsions, it can sometimes be difficult to define exactly what these compulsions are.

Here are some examples of internal compulsions:

  • Checking how you feel - for example, you might check to see if you are still in love with your partner.
  • Checking bodily sensations - for example, you might check to see if you were aroused by an intrusive thought.
  • Checking how you feel about a thought - for example, you might check whether you are still upset by the thought.
  • Repeating phrases or numbers in your head.
  • Checking if you still have a thought - for example, first thing in the morning.

You can read more about Pure O on the OCD UK website.

"Getting ready involves so much hand washing and so many mental rituals. Sometimes, I feel like staying in bed and avoiding the day."


You might find that some activities, objects or experiences make your obsessions or compulsions worse. For example if you are worried that you might stab someone then you might avoid the kitchen because you know there are knives there.

Sometimes it might feel easier to avoid situations that mean you have to do a compulsion. For example if you have to do a long and time-consuming ritual every time you leave the house, you might just decide it's easier to stay indoors. But avoiding things can have a major impact on your life.

A young man in a purple hoodie and jeans with a neutral expression, sitting outside on the ground leaning against a fence.

My OCD: A Monster in My Mind

"So strong was the fear, for a period of time I confined myself within the four walls of my room to avoid any contact with the outside world."

This information was published in May 2019. We will revise it in 2022.

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