Many children occasionally have thoughts that bother them, and they might feel like they have to do something about those thoughts, even if their actions don’t actually make sense. For example, they might worry about having bad luck if they don’t wear a favourite piece of clothing. For some children, the thoughts and the urges to perform certain actions persist, even if they try to ignore them or make them go away. Children may have an obsessive-compulsive disorder (OCD) when unwanted thoughts, and the behaviours they feel they must do because of the thoughts, happen frequently, take up a lot of time (more than an hour a day), interfere with their activities, or make them very upset. The thoughts are called obsessions. The behaviours are called compulsions. Having OCD means having obsessions, compulsions, or both.

Examples of obsessive or compulsive behaviours include:

• Having unwanted thoughts, impulses, or images that occur over and over and which cause anxiety or distress.
• Having to think about or say something over and over (for example, counting, or repeating words over and over silently or out loud)
• Having to do something over and over (for example, handwashing, placing things in a specific order, or checking the same things over and over, like whether a door is locked)
• Having to do something over and over according to certain rules that must be followed exactly in order to make an obsession go away.

Children do these behaviours because they have the feeling that the behaviours will prevent bad things from happening or will make them feel better. However, the behaviour is not typically connected to actual danger of something bad happening, or the behaviour is extreme, such as washing hands multiple times per hour.

A common myth is that OCD means being really neat and orderly. Sometimes, OCD behaviours may involve cleaning, but many times someone with OCD is too focused on one thing that must be done over and over, rather than on being organized. Obsessions and compulsions can also change over time.