In general, anxiety disorders probably arise from an excessive activation of the brain mechanism underlying fear and the fight-or-flight response.

There are several risk factors for anxiety disorders including:

  1. Temperament
  2. Environment
  3. Genetics

Biology of fight or flight response

When someone confronts a dangerous situation, two brain circuits become active and relay sensory information about the danger — such as the sight and smell of fire — to different parts of the brain. One circuit extends to the cerebral cortex, the outermost part of the brain, which is used for thinking and decision making. The other circuit involves a deeper structure called the amygdala that is central to emotional processing. The amygdala monitors the body's reactions to the environment, evaluates an event's emotional significance, and organises responses that a person may or may not be conscious of.

Although several brain circuits are activated simultaneously, the amygdala initiates a fast response to danger. It communicates with the hypothalamus at the base of the brain, prompting the quick release of hormones that raise heart rate and blood pressure, tense the muscles, and generally ready the body to fight or to flee. This system is activated before the cerebral cortex can process what is happening. This has survival value. For example, a person crossing the street may lunge out of the way of a speeding car before being consciously aware of the danger.

The amygdala also works with other brain structures to store emotional memories, including memories of frightening events. In people with anxiety disorders, however, this can become a problem. The amygdala may be so sensitive that it overreacts to situations that aren't really threatening, inadvertently triggering the brain circuits that provoke an emergency stress response. Over time, anxiety becomes attached to situations, thoughts, and memories unrelated to genuine sources of danger. In this sense, the brain may inadvertently create its own fears.


Temperament refers to a person's personality and traits. These are generally considered stable throughout a person's life. Behavioural inhibition and neuroticism are two traits that are closely associated with most anxiety disorders.

Behavioural inhibition is shown by 15 to 20% of people. It is characterised by an early-emerging and persistent tendency to display fear to new people or situations, shy and anxious behaviour with unfamiliar people, and sensitivity to approach–avoidance cues.

Neuroticism is characterised by high levels of negative emotions such as anger, irritability, worry and hostility. People who are high in neuroticism often self-critical, sensitive to the criticism of others, and feel personally inadequate.


People may be more at risk for developing an anxiety disorder if they experience a major life change that causes stress, such as the birth of a child, the loss of a close relationship, or moving to a new unfamiliar place. Physical, sexual or emotional abuse also increase the risk of developing an anxiety disorder, as do other traumatic experiences in childhood, such as the death of or separation from a parent.


Certain genetic variations may predispose people to develop anxiety disorders. A leading gene candidate is 5-HTT, a gene that regulates the neurotransmitter serotonin. Other neurotransmitters associated with anxiety are gamma-aminobutyric acid (GABA) and norepinephrine. GABA directs nerve cells to stop signalling and await further instructions.

  • Pérez-Edgar, Koraly E., and Amanda E. Guyer. “Behavioral Inhibition: Temperament or Prodrome?” Current behavioral neuroscience reports 1.3 (2014): 182–190. PMC. Web. 10 Apr. 2017.
  • Lahey, Benjamin B. “Public Health Significance of Neuroticism.” The American psychologist 64.4 (2009): 241–256. PMC. Web. 10 Apr. 2017.
  • Svihra, Martin, and Martin A Katzman. “Behavioural Inhibition: A Predictor of Anxiety.” Paediatrics & Child Health 9.8 (2004): 547–550. Print.