Biological Reasons for OCD (Obsessive-Compulsive Disorder)

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An Overview of Possible Biological Reasons for OCD

Obsessive-compulsive disorder is a mental health disorder characterized by obsessions, or unpleasant, intrusive and uncontrollable thoughts, and compulsions, which are repetitive behaviors that you feel driven to do in order to reduce the stress of the obsessions. There has been a considerable amount of research on the potential causes of this debilitating disorder, including investigations as to the biological reasons for OCD. The consensus seems to be that genetics and an insufficiency of serotonin, an important brain neurotransmitter, play an important role in the development of OCD. According to the Centre for Addiction and Mental Health, some researchers believe that frequent streptococcal infections in childhood are linked to the sudden development of OCD in children. The antibodies that fight the streptococcus infection are thought to attack the basal ganglia, the part of the brain associated with OCD. However, there is no current evidence to support the theory that streptococcal infections are related to adult-onset OCD. Children who develop OCD experience a gradual onset of the illness, not developing symptoms all at once, as is thought to occur by researchers who believe that streptococcal infections may be a cause. At this time, there is not enough evidence to support the theory.

Brain Chemistry

Serotonin is a neurotransmitter that plays a large role in maintaining mental health. Serotonin acts as a type of “feel-good” hormone which can influence mood and the development of mental health disorders such as depression, anxiety and obsessive-compulsive disorder. According to authors Mike Cardwell and Cara Flanagan in their book, “Psychology A2: The Complete Companion,” low levels of serotonin are thought to play a large role in the development of OCD. PET scans, or positron emission tomography scan, are used by researchers to study the brains of individuals with OCD. PET scan study findings have shown decreased serotonin levels in individuals with OCD as opposed to control participants. Selective-serotonin reuptake inhibitors are a type of psychotropic medication that increases the amount of serotonin in your brain. These medications have been found to be effective in the treatment of OCD.


As with many other types of mental health disorders, the development of OCD is thought to have a strong hereditary link. According to the Centre for Addiction and Mental Health, OCD does seem to run in the family, with nearly half of all cases showing some sort of hereditary correlation. It’s true that if you have a family member, especially a parent or sibling, who suffers from OCD, the likelihood is higher that you will also develop this disorder. Some studies have been focusing on whether there is a possible hereditary component involved with serotonin regulation, which may explain the increased risk of developing OCD in individuals with a family history of OCD.


“Psychology A2: The Complete Companion”; Mike Cardwell, Cara Flanagan; 2003

Centre for Addiction and Mental Health: What Causes OCD?