One of the possible factors involved with BDD is an imbalance of serotonin levels in the brain. This imbalance resembles the serotonin levels of someone with depression.

HowStuffWorks 2007

Biological Causes of Body Dysmorphic Disorder

In the arena of biological causes, researchers have begun looking for differences between the brains of healthy people and people with BDD. One study conducted by researchers at the University of California, Los Angeles shows that people with BDD may process visual information differently than people without the disorder.

Researchers showed 25 people, half with BDD and half without the disorder, three different images of faces in high, regular and low resolutions. MRI results showed that participants with BDD used the left sides of their brains -- the analytical side -- to process all three images. The other participants used their brains' left hemispheres for only the high-resolution images. This could mean the minds of people with BDD strive to acutely process visual details, even when there aren't any to process. This might be why they can see flaws in themselves, even when those flaws might not exist [source: Feusner].

Another biological factor under consideration is that people with BDD seem to have a chemical imbalance of the neurotransmitter serotonin, because they often respond well to the SSRI (selective serotonin reuptake inhibitors) class of antidepressants. Serotonin is one of the chemicals in the brain that transmits signals between the billions of neurons that constantly communicate with each other, allowing the body to think and act. Serotonin (produced in each individual neuron from an amino acid called tryptophan) is typically active in the regions of the brain responsible for emotions, sleeping and sensory perception.

During interactions between neurons, serotonin is released from the end of the first (presynaptic) neuron and picked up by the second (postsynaptic) neuron. Not all of the serotonin will be taken into the second neuron. The remainder, along with what's released from the postsynaptic neuron after use, floats within the space between the two -- called the synaptic cleft -- until enzymes destroy it. Some of the released serotonin is also reabsorbed by the first neuron.

SSRIs decrease the rate at which the serotonin is taken back into the presynaptic neuron. This causes more serotonin to linger in the synaptic cleft, also increasing the message's strength as it passes to the postsynaptic neuron. This leads to a more ideal chemical balance and seems to have a positive effect on mood. SSRI drugs include Prozac, Paxil, Zoloft and Celexa. For a more detailed explanation about serotonin and antidepressants, read How Antidepressants Work.

While doctors know that differences in brain and neurotransmitter functions exist, they don't know whether BDD causes the differences or if the differences cause BDD. However, as researchers continue to study those discrepancies, they learn valuable information about specific areas of the brain that might be targeted in BDD treatment.

But researchers are looking beyond biological links, as many cultural and psychological factors appear to influence BDD. The next section will examine how culture and personal life-events can determine the way we view ourselves.