Anxiety disorders afflict approximately 40 million American adults each year, according to the National Institute of Mental Health. Anxiety disorders can manifest in many different forms, including panic disorder, generalized anxiety disorder, obsessive-compulsive disorder and post-traumatic stress disorder. Both biological and environmental factors affect the occurrence of anxiety disorders. Important biological contributors to anxiety include genetics, brain chemistry and the body’s fight-or-flight response.
Scientists have employed identical twin studies for many years to learn more about the level of genetic influence in many different conditions. Identical twins share an identical genetic code, and evaluation of whether they also share a specific medical or mental disorder can help identify the level of genetic involvement in that disorder. Regarding anxiety disorders, researchers have discovered that identical twins are twice as likely as fraternal twins to experience a co-occurrence of an anxiety disorder, according to a 2007 article in the journal Acta Psychiatrica Scandinavica. These findings suggest that genetic factors do play a role in the manifestation of anxiety.
Researchers have recently identified genes linked to anxiety disorders. According to a 2008 article on the ScienceDaily website, researchers in Finland compared individuals with specific anxiety disorders to normal individuals and identified specific gene differences between the two groups. What’s more, the scientists found different genetic expression for the different anxiety disorders examined.
Neurotransmitters in the brain act as chemical messengers to allow different parts of the nervous system to communicate and regulate mood and behavior. Certain neurotransmitters activate behaviors while others suppress them. The role of the neurotransmitter gamma-aminobutyric acid, or GABA, is to slow down the brain, and GABA may not work properly in those with anxiety disorders, leading to a feeling of vigilance or overactivation, according to ConsumerReportsHealth.org. Certain antianxiety medications, known as benzodiazepines, increase GABA activity, hence suppressing brain activation.
At least two other neurotransmitters, particularly important in mood disorders like depression, may also play a role in anxiety—norepinephrine and serotonin. Serotonin’s potential role is evidenced by the effectiveness on anxiety of certain antidepressants that target serotonin.
The amygdala, a small almond-shaped gland in the brain, seems to play a crucial role in anxiety, according to the Office of the Surgeon General. It processes sensory information and sends an interpretation to areas of the brain that regulate fear, particularly the hypothalamus. The hypothalamus releases stress hormones through the adrenal gland. It also activates the sympathetic nervous system, which controls the heart rate, respiration and blood flow to the muscles. The sympathetic nervous system becomes highly activated during a fight-or-flight response in which you sense danger and either stay to fight or take flight to escape it. For individuals with anxiety disorders, the amygdala and hypothalamus may become overactivated due to misperception or misinterpretation of sensory signals, thus overactivating the sympathetic nervous system into a fight-or-flight response, according to the Surgeon General’s website.