Obsessive-compulsive disorder or OCD is a type of emotional and behavioural disorder that is characterised by the presence of obsessions and compulsions. Obsessions are unwanted, intrusive and recurring mental images, impulses or thoughts that cause great discomfort. Compulsions are defined as behaviours (hand washing, putting in order or checking) or mental activities (praying, repeating words or mentally counting) that are performed repetitively in response to the obsession or to following rigid rules. The main purpose behind compulsions is to prevent or lessen the anxiety caused by the obsession or to prevent a feared situation.

Younger children do not realise that these thoughts and behaviours are irrational. They find them strange and may seek their own explanations or hide them as they feel confused or ashamed. Obsessions and compulsions alike take up a lot of time and can significantly interfere with daily routines, school activities or social relationships.

The most common obsessions and compulsions in children and adolescents are the following:

• Washing rituals related to an obsession with germs or dirt.
• Fear of something serious happening (accidents, fires, the death or illness of a family member or the patient him/herself)
• Rituals related to order or symmetry.
• Repetition or checking rituals.
• Fear of hurting or harming someone.
• Obsession with counting repeatedly.
• Compulsions when eating, sleeping or saying goodbye to others.

The severity of obsessive-compulsive disorder (OCD) varies a great deal, from few symptoms with a low degree of impairment, to severe presentations with debilitating effects on the child or adolescent’s development.

We have to bear in mind that ritualistic behaviours might be observed during several stages of the child’s development that are not due to any disorder and that are part of normal developmental rituals, such as a preference for certain games, an interest in symmetry or counting, jumping to avoid lines on the ground, etc. Children experience these routines as a game; rituals can be interrupted without making the person feel unwell and they do not interfere in normal activities.

Body dysmorphic disorder

In cases of obsessive-compulsive disorder (OCD) with body dysmorphic disorder, the patient is excessively concerned about one or more defects or imperfections in their physical appearance which are not noticeable or are of little importance to other people. Due to this concern, they start with a series of behaviours such as repeatedly looking in the mirror, checking their appearance and spending a lot of time on these concerns and behaviours. In order for the symptoms to be considered pathological, these concerns about one part of their physical appearance must be much more frequent, intense and distressing than the typical concerns about their personal image that adolescents often experience.

Hoarding disorder

In cases of hoarding disorder, children and young people experience great difficulty in disposing with objects and possessions regardless of their value. They feel the need to hold onto things and are very upset when they have to get rid of them. This difficulty causes them to accumulate objects, and their living space is overflowing with items they do not need.

Other disorders

There are other disorders that are also related to obsessive-compulsive disorder, such as trichotillomania, or hair pulling disorder, which consists of repeatedly pulling out one’s own hair, and excoriation disorder, in which the child or adolescent repeatedly scratches their own skin to the point that skin lesions may occur. All of these disorders cause discomfort and interfere with the child’s family, social or academic life.