How is brain chemistry related to anxiety disorders?

For decades, scientists have believed that anxiety is related to abnormalities in brain chemistry. They base this conviction on the effects of drugs that reduce anxiety by increasing the availability of certain neurotransmitters in the brain. The first anti-anxiety drugs were benzodiazepines, which raise levels of the neurotransmitter gamma-aminobutyric acid (GABA). Later, drugs that increase serotonin levels and affect norepinephrine and other neurotransmitters associated with mood also proved effective.

Several regions of the brain influence anxiety. The amygdala is associated with emotions and coordinates the body's response to fear. The cerebral cortex evaluates data about a perceived threat and forms judgments about it, shaping the response to fear. The hippocampus processes emotions and long-term memories. The locus ceruleus helps determine which stimuli deserve attention. The prefrontal cortex is involved in complex reasoning, decision making, and social behavior, and it seems to play a role in subduing the fear response.