OCD is usually grouped into five main themes: checking, contamination, symmetry and ordering, intrusive thoughts (sometimes called Pure O), and hoarding, though these overlap and OCD can fix on almost any fear.
Themes, not fixed types
It helps to think of OCD as a single condition that shows up in different themes rather than as a set of separate types. OCD-UK describes the five themes below as the most common, but stresses that a person can have one theme or several at once, that themes often overlap, and that there are in effect infinite forms because OCD tends to latch onto whatever matters most to someone. The shape stays the same: an unwanted obsession that causes anxiety, and a compulsion done to ease it. The NHS explains that the relief never lasts, so the cycle repeats.
The five common themes
- Checking. Fears about harm, danger or something going wrong, eased by repeated checking. The NHS gives the example of worrying you will set the house on fire by leaving the cooker on, so you check it again and again.
- Contamination. Fears about germs, dirt, illness or feeling “dirty”, leading to washing, cleaning and avoidance. The contaminated feeling does not always come from touching something - it can be a purely felt, or “mental”, contamination.
- Symmetry and ordering. A need for things to feel “just right”, balanced or orderly, with arranging, counting and ordering. The NHS example is needing all the tin labels in a cupboard to face the same way.
- Intrusive thoughts (“Pure O”). Unwanted, distressing thoughts, images or urges, often violent, sexual, religious or about relationships, with mostly hidden mental rituals rather than visible ones. See the qualifier below, because this is the theme parents worry about most.
- Hoarding. Difficulty letting go of items, sometimes driven by a specific obsessive fear. See the note below on how hoarding now sits in the diagnostic system.
Two corrections worth knowing
First, on intrusive thoughts. OCD Action points out that everyone has unwanted intrusive thoughts; in OCD they are distressing precisely because they clash with the person's own values. There is no evidence that these thoughts mean someone is dangerous or will act on them. If your child describes frightening thoughts, that distress is a sign of how much the thoughts upset them, not a warning.
Second, on hoarding. It was long treated as part of OCD, but hoarding disorder was reclassified as a condition in its own right in DSM-5 in 2013. Some people who hoard are still diagnosed with OCD rather than hoarding disorder, because their hoarding is driven by a specific obsessive fear. So whether hoarding counts as “a type of OCD” depends on what is driving it.
OCD in children
The same themes apply to children and young people. The Royal College of Psychiatrists describes OCD as an anxiety-related condition that can disrupt school, homework and friendships. A GP or school nurse can refer a child to CAMHS, and effective treatment is available: cognitive behavioural therapy with exposure and response prevention, and sometimes medication. This page is general information, not medical advice. If you are worried about your child, speak to your GP. If anyone is at immediate risk of harm, call 999, and you can reach Samaritans free any time on 116 123 or the YoungMinds Parents Helpline on 0808 802 5544.
Where the law comes from
This page is general information, not clinical or legal advice.