Many children experience repetitive thoughts and behaviours. A preschooler may insist on having the same book read to her every night for several months. A middle-schooler may frequently express his displeasure about attending a new after-school program. But these kinds of typical behaviours differ from the more intense, enduring and impairing obsessions and compulsions that are the hallmarks of obsessive-compulsive disorder (OCD).

Obsessions involve recurrent and persistent thoughts or images that are intrusive, unwanted and time-consuming, taking more than an hour per day. Compulsions, meanwhile, are repetitive behaviours or mental acts that a child feels obliged to do, typically to relieve distress associated with an obsession. Young people with OCD usually experience both obsessions and compulsions. These may include fear of contamination, fear of being aggressive, wanting to make things “just right,” as well as distressing sexual or religious thoughts. For more information, see Vol. 16, No. 1 of the Children’s Mental Health Research Quarterly.