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This small nucleus contains almost half of all the brain neurons that use norepinephrine as a neurotransmitter. The locus coeruleus also projects its axons to those parts of the brain that may be associated with panic disorders (the amygdala, hippocampus, septum, cortex, brainstem, reticular formation, etc). Stimulating an animal's locus coeruleus, like stimulating its amygdala, produces anxiety behaviours.
Anxiety disorders can also run in families, suggesting that a combination of genes and environmental stresses are to blame. The role of brain chemistry is also being investigated. Besides the primary cause of hormonal fluctuations, other medical and psychological conditions can cause or contribute to anxiety. Some mental health experts explain that, psychologically speaking, anxiety is often the result of unexpressed negative feelings about some problem in our lives.