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In spite of a range of theories and considerable research, scientists so far have not been able to identify a definitive cause for a person developing Obsessive-Compulsive Disorder (OCD).
However, whilst this may be the case, it is believed that OCD is likely to be the result of a combination of either neurobiological, genetic, behavioural, cognitive, or environmental factors that trigger the disorder in a specific individual at a particular point in time. Below is a summary of some of the suggested theories around the cause of OCD.
Biological factors relating to the possible causes of OCD are an area of considerable research and theory. However, despite the recognition that certain parts of the brain are different in OCD sufferers, when compared with non-sufferers, it is still not known how these differences relate to the precise mechanisms of OCD.
Biological causes of OCD have focused on a circuit in the brain which regulates primitive aspects of our behaviour such as aggression, sexuality, and bodily excretions. This circuit relays information from a part of the brain called the orbitofrontal cortex (front part of the brain), to another area the striatum, and the thalamus (deeper parts of the brain). It also includes other regions such as the caudate nucleus of the basal ganglia. When this circuit is activated, these impulses are brought to your attention and cause you to perform a particular behaviour that appropriately addresses the impulse.
For example, after a visit to the bathroom, you may begin to wash your hands to remove any harmful germs you may have encountered. Once you have performed the appropriate behaviour — in this case, washing your hands — the impulse from this brain circuit diminishes and you stop washing your hands and go about your day. It has been suggested that if you have OCD, your brain has difficulty turning off or ignoring impulses from this circuit. This, in turn means the obsessions and compulsions continue, leading you to wash your hands again and again.
Abnormalities, or an imbalance in the neurotransmitter, or brain chemical, serotonin, could also be to blame. Serotonin is the chemical in the brain that sends messages between brain cells and it is thought to be involved in regulating everything from anxiety, to memory, to sleep. Medications known as Selective Serotonin Re-uptake Inhibitors (SSRIs) are often used to treat OCD, although it is not fully known why the SSRI medications seem to help some people with OCD.
Brain imaging studies have been used to show the differences between the brains of people with OCD and those without OCD, but the scientific community is split over whether what researchers have found is a cause for, or a result of, having the disorder.
How the Brain Cells and Chemicals Work
The job of your nerve cells is to send messages back and forth like a telephone wire. But nerves aren’t a single string — they’re made of lots of interconnected cells. So they act more like the game ‘telephone’, where one person whispers a message to the next, and it’s passed down to the end of the line one person at a time. Instead of words, the ‘message’ is passed by chemicals called neurotransmitters that are sent by one cell to the next in line.
These chemicals are sent out by one nerve cell into the space between it and then the next cell. The next cell in line gets the message once those chemicals get to it from across the gap. Then that nerve cell releases a chemical toward the next nerve cell so it gets the message.
It’s important that the right amount of chemical is sent or the message might be heard wrong.
A key chemical involved in OCD is called serotonin. And a key gene for this process is hSERT. hSERT has the instructions for making a serotonin transporter. The transporter’s job is to mop up extra serotonin after a nerve splits it towards the next nerve cell in line. In some people with OCD, hSERT works too fast, and may collect all the serotonin before the next cell has even heard the signal! Their nerves are whispering when they should be speaking out loud.
One type of drug used to treat people with OCD slows down the collection of serotonin by transporters like hSERT. This means that serotonin stays in the space between the cells longer and increases the chances that the second cell will get the message which helps prevent some OCD symptoms.
Scientists have found that another gene called SLC1A1 might be involved. This gene is similar to hSERT, but is in charge of soaking up a different neurotransmitter called glutamate.
Research funded by the National Institute of Mental Health (NIMH), based in the US, examined DNA samples from patients with OCD and related illnesses, and the results suggest that OCD may be associated with a rare combination of two mutations within the human serotonin transporter gene (hSERT). Firstly, the hSERT gene codes for the human serotonin transporter and secondly the membrane protein responsible for the reuptake of serotonin from the synapse between two neurons. It is the transporter protein that is bound by serotonin reuptake inhibitors (SSRIs), resulting in blocking the transporter’s function and leaving more serotonin available for neuronal communication within the synapse.
The researchers discovered a mutation within the hSERT gene, which they labeled I425V. The mutation appears to be associated with an increased expression of the hSERT gene, resulting in more transporter proteins appearing in the neuron’s membrane. This results in increased reuptake of serotonin in those neuronal synapses, decreasing the amount of serotonin available in the synapse for signalling. The second mutation identified, a long allele of the promoter portion of the serotonin transporter gene (5-HTTLPR), results in similar cellular effects—an increase in transporter proteins leading to less serotonin being available for neuronal communication.
The two mutations appearing together result in a significantly lower amount of serotonin available within the synapse than is seen with either one of the mutations alone, resulting in greater biochemical effects and more severe symptoms.
Other research has revealed that there may be a number of other factors that could play a role in the onset of OCD, including behavioural, cognitive, and environmental factors. Research has revealed a great deal about the psychological factors that maintain OCD, which in turn has led to effective psychological treatment in the form of Cognitive Behavioural Therapy (CBT). For example, according to the Learning Theory, OCD symptoms are a result of a person developing learned negative thoughts and behaviour patterns, towards previously neutral situations which can result from life experiences.
Many cognitive theorists believe that individuals with OCD have faulty beliefs, and that it is their misinterpretation of intrusive thoughts that leads to OCD. According to the cognitive model of OCD, everyone experiences intrusive thoughts from time-to-time. However, people with OCD often have an inflated sense of responsibility and misinterpret these thoughts as being very important and significant which could lead to catastrophic consequences. The repeated misinterpretation of intrusive thoughts leads to the development of the obsessions and because the thoughts are so distressing, the individual engages in compulsive behaviour to try to resist, block, or neutralise the obsessive thoughts.
Some researchers believe that this theory questions the biological theory because people may be born with a biological predisposition to OCD but never develop the full disorder, while others are born with the same predisposition but, when subject to sufficient learning experiences, develop OCD.
Stress and parenting styles are environmental factors that have been blamed for causing OCD, but no evidence is yet to show that stress, or the way a person interacted with his or her parents during childhood, causes OCD.
Stress does not cause OCD, although a stressful event, like being involved in or witnessing a road traffic accident, may trigger its onset. If left untreated, everyday anxiety and stress in a person’s life will worsen symptoms in OCD. Problems at school or work, university exam pressures and normal everyday problems that relationships can bring are all contributory factors to increasing the frequency and severity of a person’s OCD.
Some children begin to exhibit symptoms after a severe infection such as strep throat. It is thought that the body's natural response to infection, the production of certain antibodies, when directed to parts of the brain might be linked in some way to Paediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infection (PANDAS). Studies suggest the infection doesn’t actually cause OCD, but triggers symptoms in children who are genetically predisposed to the disorder. It is thought that if OCD results from a strep throat infection the symptoms will start quickly, probably within one or two weeks.
Another interesting line of research is in the area of genetics, and recent studies have indicated that there may be a considerable genetic basis for OCD. Some research points to the likelihood that OCD sufferers will have a family member with the OCD or with one of the other disorders in the OCD ‘Spectrum’. However, the theory that OCD is inherited genetically is not conclusive - for example, identical twins will not necessarily both have OCD. So although the genetics may play a part, they aren’t the whole story and learned or environment factors may play a part.
Nobody really knows what other factors might be involved - perhaps an illness or even ordinary life stresses could induce the activity of genes associated with the symptoms of OCD.
Commonly accepted in the past, but nowadays increasingly disregarded, the psychoanalytic theory suggests that OCD develops because of a person’s fixation arising from unconscious conflicts or discomfort they experienced during infancy or childhood. This theory is now quite rightly disregarded due to the failure of psychoanalytic therapy to treat OCD.
Major stresses or traumatic life events may precipitate the onset of OCD. However, these are not thought to cause the OCD, but rather trigger it in someone already predisposed to the disorder.
Depression is also sometimes thought to cause OCD, although again opinion is split, with the majority of experts believing that depression is often a symptom of OCD rather than a cause.
There is still a great deal of theoretical contention surrounding the definitive cause of OCD. However, all of the above theories offer compelling and highly informative insights, with the possibility that a combination of the theories may eventually be identified as the actual cause of OCD. Whilst the cause is currently still being debated, sometimes vigorously by the scientists, what is not in contention is the fact that Obsessive-Compulsive Disorder is indeed a chronic, but equally a very treatable medical condition.