Obsessive compulsive disorder (OCD) is characterized by obsessions and compulsions, such as obsessive, repetitive thoughts and compulsive behavior like counting, cleaning and hand washing. While as many as 1 in every 200 adolescents and children are affected with OCD, there have not been many studies that target obsessive compulsive disorder in children to determine whether small children can develop a full-blown case of OCD that is as severe as the OCD found in adolescents. If left untreated, OCD can affect children in marked ways, by hindering development and increasing the severity of symptoms.

To find out more about children and OCD, the Bradley Hasbro Children's Research Center performed a study on small children with OCD. The study is the largest known study of young children at this time. The participants consisted of 58 children - 35 girls and 23 boys - that were very young - between four and eight. Nearly 20 percent had been medically treated for OCD already, while 24 percent had undergone psychotherapy for OCD. Also, over 20 percent had been diagnosed with attention deficit hyperactivity disorder (ADHD), 20 percent were diagnosed with generalized anxiety disorder (GAD), and 20 percent had a history of OCD in their first-degree family.

The children in the study had multiple obsessions and compulsions, with a reported average of four compulsions present in each child. The children's obsessions included fear of death (themselves and loved ones), fear of catastrophic events and fear of contamination. The most noted obsession was hand repeated hand washing.

All of the young children were given a series of psychological tests and clinical assessments. In the end, the study showed that children as young as four years old can develop a full-blown case of OCD (like many other mental impairments, a condition that may receive consideration for social security disability). In fact, they seem to show a lot of the same characteristics seen in adolescents with the condition. The symptoms, severity, and diagnoses were almost completely the same for the younger children as the adolescents. The study was published online by the Journal of Psychopathology and Behavioral Assessment.

There were two large noted differences by the researchers: younger children had less depression, compared to the adolescents, and younger children had a higher ratio of girls, whereas adolescents had a higher ratio of boys.