Intrusive thoughts: what they are, why they happen and how to get help

The NHS describes obsessions as unwanted, intrusive and often distressing thoughts, images or urges that repeatedly enter the mind. They typically bring intense anxiety or distress.

The NHS says almost everyone has unpleasant or unwanted thoughts at some point. What marks out an obsession, according to the NHS, is a persistent, unpleasant thought that dominates your thinking to the extent that it interrupts other thoughts.

The NHS is explicit that thoughts of a violent or sexual nature that you find repulsive or frightening are just thoughts, and having them does not mean you will act on them.

Intrusive thoughts on their own are not a diagnosis. The NHS says OCD has 3 main elements: obsessions, the intense anxiety or distress they cause, and compulsions, which are repetitive behaviours or mental acts that the person feels driven to perform. The compulsion temporarily relieves the anxiety, but the obsession and anxiety soon return and the cycle starts again.

The NHS says most people with OCD realise the compulsive behaviour is irrational, but cannot stop and feel they need to do it "just in case". Compulsions are not always visible to others, and may be mental, such as repeating words in the head or thinking "neutralising" thoughts.

The NHS says the two main treatments are talking therapy and medicine, and the treatment recommended depends on how much OCD is affecting your life. A short course of therapy is usually recommended for relatively mild OCD, while more severe OCD may need a longer course of combined therapy and medicine.

The talking therapy is usually cognitive behavioural therapy (CBT) with exposure and response prevention (ERP). The NHS describes this as working with a therapist to break problems into parts, then facing your fears and having obsessive thoughts without neutralising them with compulsive behaviours, starting with situations that cause the least anxiety. It says people with fairly mild OCD usually need about 8 to 20 sessions, with exercises at home between sessions.

The NHS says medicine is usually a type of antidepressant called an SSRI, which may be needed if therapy does not help or OCD is fairly severe. You may need to take it for up to 12 weeks before you notice any benefit, and most people need treatment for at least a year. Do not stop an SSRI without speaking to your doctor, because suddenly stopping can cause unpleasant side effects.

If talking therapy and medicine do not control the OCD, the NHS says further treatment by a specialist team may be needed, and some people are referred to a national specialist OCD service.

The NHS says women can sometimes have OCD during pregnancy or after their baby is born. Obsessions may include worrying about harming the baby or not sterilising feeding bottles properly, and compulsions could include repeatedly checking the baby is breathing. These intrusive, unwanted and unpleasant thoughts, images or urges can cause anxiety and lead to repetitive behaviours.

The NHS advises that if you keep getting these thoughts and they affect your daily life, you should speak to your GP or health visitor, who can support you or refer you to a specialist mental health team. It also notes OCD sometimes starts after an important life event such as childbirth or a bereavement.

SSRIs can be prescribed in pregnancy, according to the NHS, depending on whether your GP thinks the benefits outweigh the risks, so it is worth talking this through rather than avoiding help.

The NHS says it is not clear what causes OCD, and that several factors may play a part. These are family history, differences in the brain such as areas of unusually high activity or low levels of serotonin, life events such as being bullied, abused or neglected, or an event such as childbirth or bereavement, and personality, including people with high personal standards, a strong sense of responsibility or who are generally quite anxious.

The NHS says OCD can affect men, women and children, and that people can start having symptoms from as early as 6 years old, though it often begins around puberty and early adulthood.

If you are under 18, or want to help someone under 18, the NHS points to its pages on getting mental health support for children and young people. A GP is the usual first step.

The NHS says it is important to get help if you think you have OCD and it is having a significant impact on your life. People are sometimes reluctant to seek help because they feel ashamed or embarrassed, but the NHS says OCD is a health condition like any other, having it does not mean you are "mad" and it is not your fault.

There are 2 main routes: refer yourself directly to an NHS talking therapies service, or see a GP. The NHS says to contact a GP or care team immediately if you ever feel you cannot go on, and that you can call Samaritans on 116 123 or contact NHS 111. In an emergency, call 999.

On the NHS you do not need a GP referral for talking therapies, because you can refer yourself. Waiting times vary by area and service. People with severe, long-term OCD that has not responded to local treatment may be referred to a national specialist OCD service.

Private therapists and psychologists also offer CBT with exposure and response prevention, usually self-paid. It is worth checking that a therapist has specific training in OCD and is registered with a recognised professional body.