Obsessive compulsive disorder (OCD) is an anxiety disorder which is characterized by intrusive thoughts (obsessions) that result in worry and repetitive behaviors (compulsions) aimed at alleviating the anxiety. While most of us have run back into the house to check the stove was turned off, people suffering from OCD experience these thoughts more frequently, and to the point that it becomes alienating and all-consuming. But what causes it?

While the exact cause of OCD is not completely elucidated, researchers believe that it results from a combination of genetics and environmental factors. Genetic studies have linked a specific mutation in the serotonin transporter gene to the manifestation of OCD. Additional data from studies on identical twins have corroborated these results.

However, the studies also show that genetics accounts for only 40-65% of the risk for developing OCD, thus indicating that environmental factors also play a role in manifestation of the disease. Reports suggest the potential for a number of different environmental risk factors including strep infections, anxiety, emotional instability, depression, handwriting difficulties, behavioral aggression, and oppositional behaviors.

Differences in the physical structure of the brain are also a prominent factor in patients with OCD. In fact, neuroimaging techniques have revealed structural and volumetric abnormalities in the brains of these patients: People with OCD have a patterned increase in grey matter in the brain in certain areas and a decrease in others.

Other studies have examined the role for a potential chemical imbalance in the brain leading to disease symptoms. From a molecular perspective, data show that in fact neurotransmitter dysregulation does play an important role in the manifestation of OCD symptoms. More specifically, reports indicate that the neurotransmitters serotonin and dopamine are associated with the pathophysiology of OCD. Scientists show that patients with OCD may experience an increase in dopamine in the prefrontal cortex and/or a decrease in serotonin in the basal ganglia.

Currently used medications for managing the disorder including Clomipramine (Anafranil), Zluvoxamine (Luvox), Fluoxetine (Prozac), Paroxetine (Paxil, Pexeva), and Sertraline (Zoloft) specifically focus on regulating these neurotransmitter levels in the brain. Selective serotonin re-uptake inhibitors (SSRIs) decrease symptoms of OCD in two-thirds of adults and children who take them.

While there are a number of available medications for treating OCD symptoms, they come with unique risks. Similar to other psychological disorders, the choice of which mediation to use is often the result of trial and error, and drug interactions must be carefully considered. Furthermore, side effects may include an upset stomach, sleep disturbances, sweating, and a decrease in libido. It is hoped that additional research into the causes and molecular mechanism of OCD will ultimately lead to more effective and safe drugs for treating disease symptoms.

References

Cath, D., Grootheest, D., Willemsen, G., Oppen, P., & Boomsma, D. (2008). Environmental Factors in Obsessive-Compulsive Behavior: Evidence from Discordant and Concordant Monozygotic Twins Behavior Genetics, 38 (2), 108-120 DOI: 10.1007/s10519-007-9185-9

Harsányi A, Csigó K, Demeter G, & Németh A (2007). [New approach to obsessive-compulsive disorder: dopaminergic theories]. Psychiatria Hungarica : A Magyar Pszichiatriai Tarsasag tudomanyos folyoirata, 22 (4), 248-58 PMID: 18167420

Kim CH, Cheon KA, Koo MS, Ryu YH, Lee JD, Chang JW, & Lee HS (2007). Dopamine transporter density in the basal ganglia in obsessive-compulsive disorder, measured with [123I]IPT SPECT before and after treatment with serotonin reuptake inhibitors. Neuropsychobiology, 55 (3-4), 156-62 PMID: 17657168

Ozaki N, Goldman D, Kaye WH, Plotnicov K, Greenberg BD, Lappalainen J, Rudnick G, & Murphy DL (2003). Serotonin transporter missense mutation associated with a complex neuropsychiatric phenotype. Molecular psychiatry, 8 (11), 933-6 PMID: 14593431

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