Obsessive Compulsive Disorder (OCD) is a mental health disorder wherein a patient has recurring, uncontrollable obsessions and compulsions. Obsessions are unwanted, repeated thoughts, urges or images that cause intense anxiety and distress, while compulsions are repetitive behaviors that the patient feels compelled to perform in response to these obsessions and/or to reduce his distress. While the etiology of the disorder is not yet fully understood, it is known that genetics, differences in brain structure and function and environmental factors such as childhood abuse or trauma, can all play a role in developing OCD. The disease has been estimated to affect 1 in 100 adults and 1 in 200 children. It can occur at any age. However, it is commonly seen to have an onset between the ages of 8 and 12 years or between the late teen years and early adulthood.
Treatment for OCD includes medication, psychotherapy, or a combination of both. Medications commonly used to treat OCD include serotonin reuptake inhibitors (SRIs), selective serotonin reuptake inhibitors (SSRIs) and antipsychotic drugs. Psychotherapy mainly involves Exposure and Response Prevention (EX/RP), a type of cognitive behavioral therapy (CBT) that is effective in reducing compulsive behaviors.
Genetic susceptibility to OCD follows an autosomal dominant pattern of inheritance. The disorder is linked to SNPs in three genes: SLC6A4, HTR2A and BDNF. The gene SLC6A4 encodes a neurotransmitter transporter that takes up serotonin released in the brain synapses into the presynaptic neurons, thereby terminating its synaptic actions and recycling it into the neurotransmitter pool. The SNP rs28914832 in the SLC6A4 gene results in the Ile425Val substitution and has been found to increase susceptibility to OCD. Another polymorphism in the promoter region of this gene, referred to as 5-HTTLPR and consisting of a 44 bp indel, was also associated with OCD. The gene HTR2A encodes a serotonin receptor located on the postsynaptic membranes. The SNP 1438G>A, located in the promoter region of this gene, is found to be associated with OCD. The BDNF gene encodes a neurotrophic factor essential for the survival of striatal neurons in the brain. The SNP 196G-A in this gene results in the Val66Met substitution and is believed to confer protection against OCD.