The etiologies of OCD have "not yet been identified" (What Causes OCD - College Students), but there are possible causes that triggers OCD and contribute to its development. However, one should note that the cause does not come from physiological effects of a substance, such as intake of drug and medication.

    • Before, etiologies of OCD was attributed largely to sociocultural issues, such as interaction and relationship with family during childhood. Now, many researchers are assuming that OCD has great causes from biological factors, especially on brain functionality and neurotransmitter more than from cognitive or sociocultural factors.
    • One probable cause is through genetic inheritance. OCD "sometimes runs in families" (Eating Disorders) and a person diagnosed of OCD is likely to have another immediate family member with OCD; hence there is high possibility that OCD can be genetically inherited. Nonetheless, genetics only plays a part in etiologies of OCD.
    • Functionality of the brain is another cause of OCD. There are parts of the brain that are "involved in fear and anxiety" (Eating Disorders): orbitofrontal cortex, striatum and the thalamus, including caudate nucleus of the basal ganglia. In these parts of the brain, "a circuit...regulates primitive aspects of our behavior…[which] relays information " to each part, and as the circuit activates, these impulses motivate one to "perform a particular behavior that appropriately addresses the impulse" (What Causes OCD?). People diagnosed of OCD have difficulty "ignoring impulses from this circuit", which in other words, means obsession and repetitive behaviors or compulsion (What Causes OCD?).
    • Another strongly supported etiology of OCD is the abnormality caused by gene mutation and unbalance of neurotransmitter, particularly serotonin. This neurotransmitter is "involved in regulating everything from anxiety, to memory, to sleep" (What Causes OCD?). Within the functionality of serotonin, hSERT can be identified. This contains genes or "instructions for making a serotonin transporter" (What Causes OCD?), which functions as cleaning worker: it "mop up extra serotonin after a nerve splits it towards the next nerve cell in line" (What Causes OCD?). Research by National Institute of Mental Health (NIMH) showed that hSERT in people with OCD "works too fast", which is the result of uncommon and abnormal mutation (What Causes OCD?). Hence, all serotonins are cleared and collected by increased number of hSERT, "decreasing the amount of serotonin available in the synapse for signaling" in the next line (What Causes OCD?). Due to significantly high level of serotonin delivered at once, the level of anxiety boosts up increasingly. This develops toward obsession with compulsion. In a similar manner, NIMH also discovered that SLC1A1 might also be involved. This gene soaks up another neurotransmitter, glutamate.
    • But there is uncertainty over this biological etiologies because the researchers do not know whether it "is a cause for, or a result of, having the disorder" (What Causes OCD?).

    • From cognitive aspect, compulsions are the result of "learned responses that help someone reduce or prevent anxiety...associated with obsessions" (What Causes OCD - College Students). Hence, behaviors of a person with OCD is the result of Learning Theory; person with OCD is "developing learned negative thoughts and behavior patterns, towards previously neutral situations...from life experiences" (What Causes OCD?).
    • The misinterpretations of "faulty or dysfunctional beliefs" or "intrusive thoughts" as important and significant thoughts is another cognitive factor leading to OCD (What Causes OCD - College Students). These thoughts are categorized in "six types of faulty or dysfunctional beliefs" (What Causes OCD - College Students): inflated responsibility (one has responsibility to prevent negative outcomes); over importance of thoughts/thought-action fusion (either that bad thought can influence the probability of a negative event or having bad thoughts to occur is morally equivalent to actually doing it); control of thoughts; overestimation of threat; perfectionism; and intolerance for uncertainty (importance of knowing, "without a doubt, that negative events won't happen" (What Causes OCD - College Students).
    • People with OCD cannot dispose or be senseless to these thoughts. They are "plagued by [and unable to]... banish them from their mind, no matter how hard they try" (Human Body and Mind). In other words, they are unable to control these thoughts that overwhelm their brain. These finally lead and develop to obsessions. To reduce the obsession, person does repetitive behavior and rituals to "try to resist, block, or neutralize them" (What Causes OCD - College Students).

As they are unable to dispose intrusive thoughts, they are hunted by them.
Pruitt, D. Sharon. Photograph. Web. 20 Mar. 2012. <http://nopsa.hiit.fi/pmg/viewer/images/photo_206812690_b25e70627d_t.jpg>.

    • There are less causes from sociocultural perspective. Only few research experiments have been conducted to verify the cause in one's environment. Some assumptions of possible etiologies are: parent-child relationship and interaction during childhood. Stress, "a severe infection such as strep throat" and "traumatic life events" does not cause OCD (What Causes OCD?); however, they may trigger OCD to occur "in someone who is predisposed", and worsen the symptom (What Causes OCD - College Students).

<Works Cited>
"Human Body and Mind - Obsessive Behaviour." BBC - Homepage. British Broadcasting Corporation. Web. 19 Feb. 2012. <http://www.bbc.co.uk/science/humanbody/mind/articles/disorders/ocd.shtml>.
"Mental Illnesses - Anorexia Nervosa." NAMI. National Alliance on Mental Illness. Web. 27 Feb. 2012. <http://www.nami.org/Template.cfm?Section=By_Illness>.
Smith, Melinda, and Jeanne Segal. "Anorexia Nervosa." : Signs, Symptoms, Causes, And Treatment. Jan. 2012. Web. 27 Feb. 2012. <http://helpguide.org/mental/anorexia_signs_symptoms_causes_treatment.htm>.
"What Causes OCD - College Students." OCD Symptoms, Causes, Treatment and Support Information. OCD Chicago. Web. 27 Feb. 2012. <http://www.ocdchicago.org/index.php/college/what_causes_ocd/>.
"What Causes OCD?" OCD-UK Supporting Children and Adults Affected by Obsessive-Compulsive Disorder. Web. 27 Feb. 2012. <http://www.ocduk.org/what-causes-ocd>.