Some people with OCD have areas of unusually high activity in their brain, or low levels of the chemical serotonin, which is a neurotransmitter that some nerve cells use to communicate with each other, and is thought to be involved in regulating many functions, influencing emotions, mood, memory, and sleep. Autoimmune
A controversial hypothesis is that some cases of rapid onset of OCD in children and adolescents may be caused by a syndrome connected to Group A streptococcal infections (GABHS), known as pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS). OCD and tic disorders are hypothesized to arise in a subset of children as a result of a post-streptococcal autoimmune process. The PANDAS hypothesis is unconfirmed and unsupported by data, and two new categories have been proposed: PANS (pediatric acute-onset neuropsychiatric syndrome) and CANS (childhood acute neuropsychiatric syndrome). The CANS and PANS hypotheses include different possible mechanisms underlying acute-onset neuropsychiatric conditions, but do not exclude GABHS infections as a cause in a subset of individuals. PANDAS, PANS, and CANS are the focus of clinical and laboratory research, but remain unproven. Whether PANDAS is a distinct entity differing from other cases of tic disorders or OCD is debated.A review of studies examining anti-basal ganglia antibodies in OCD found an increased risk of having anti-basal ganglia antibodies in those with OCD versus the general population. Environment
OCD may be more common in people who have been bullied, abused, or neglected, and it sometimes starts after a significant life event, such as childbirth or bereavement.
Cutaneous meningioma (also known as "Heterotopic meningeal tissue," and "Rudimentary meningocele") is a developmental defect, and results from the presence of meningocytes outside the calvarium. : 622

See also
List of cutaneous conditions


== References ==