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If you have obsessive-compulsive disorder, you have disturbing thoughts, images or urges that you just can't get out of your head. You also do certain things over and over again, even though you don't want to.

Disturbing thoughts are called obsessions. For example, you might be very worried about dirt and germs.

Things you do over and over again are called compulsions. For example, you might wash your hands a lot.

Some people with obsessive-compulsive disorder only get one of these problems, but it's common to get both.¹

Obsessive-compulsive disorder is often called OCD for short. It belongs to the group of conditions called anxiety disorders.²

People with anxiety disorders feel extremely fearful and worried for no reason. Other anxiety disorders include panic attacks, post-traumatic stress disorder and phobias (where you feel very frightened of a particular thing or situation).

For most people, there's a link between the disturbing thoughts and the compulsive behavior.² For example, if someone is worried about whether an electrical appliance is safe, they may check over and over again to make sure it's switched off. Someone who's worried about germs may wash their hands all the time.

People do these compulsive things to try to control their anxiety and make their worrying thoughts go away. But doing these things can start to take up more and more of your time. If you have severe OCD, your compulsions take up so much of your time that they interfere with your work, your daily routines, your social life and your relationships.³

Some people with OCD feel embarrassed or frustrated about their condition. You may not like talking about it. And it sometimes takes time for doctors to spot the condition and recommend the right treatment.⁴ But it is important to make the effort to see a doctor. There are treatments that can help you. You can ask your doctor to refer you to someone with experience in treating OCD.

OCD is more common in women than in men.^{5 6}

It usually starts when you're a child, a teenager or a young adult.⁷ It's more common for boys to have OCD than girls.⁸ However, lots of children have habits, such as biting their nails or playing with their hair. These are normal, and won't usually have anything to do with OCD.

There's no single cause of OCD. It may be caused by a mixture of things. These could be:^{9 10 11 12 13 14 15}

• The genes you inherit from your parents
• Things that happen in your life
• The way you think about the world
• Problems with the way signals travel in your brain. This may happen because you have low amounts of a chemical in your brain called serotonin.

Some things seem to make it more likely that someone will get OCD. These are:^{6 16}

• Having other people with OCD in your family
• Coming from a higher-income background
• Taking cocaine
• Having drink problems in the past
• Being depressed or anxious
• Having a phobia (this means you're very frightened of a particular thing or situation).

People who are single or unemployed have a higher chance of having OCD.^{6 16} But it might be that OCD makes it harder to find a partner or keep a job.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.