Causes of Anxiety
The causes of anxiety are often varied and complex.
A number of factors may cause anxiety disorders
• Environmental factors (such as pollution)
• Physical (such as illness)
• Developmental issues
• Trauma (including attachment)
Natural History of Anxiety
In addition, studies are being conducted on the "natural history" (what course the illness takes without treatment) of a variety of individual anxiety disorders, combinations of anxiety disorders, and anxiety disorders that are accompanied by other mental illnesses such as depression.
Combinations of Factors
Scientists currently think that, like heart disease and type 1 diabetes, mental illnesses are complex and probably result from a combination of genetic, environmental, psychological, and developmental factors.
For instance, although studies of twins and families suggest that genetics play a role in the development of some anxiety disorders, problems such as PTSD are triggered by trauma. Genetic studies may help explain why some people exposed to trauma develop PTSD and others do not.
The Roles of the Amygdala and Hippocampus in Anxiety
Several parts of the brain are key factors in the causes of anxiety and fear. Using brain imaging technology and neurochemical techniques, scientists have discovered that the amygdala and the hippocampus play significant roles in most anxiety disorders.
The amygdala is an almond-shaped structure deep in the brain that is believed to be a communications hub between the parts of the brain that process incoming sensory signals and the parts that interpret these signals. It can alert the rest of the brain that a threat is present and trigger a fear or anxiety response.
It appears that emotional memories are stored in the central part of the amygdala and may play a role in anxiety disorders involving very distinct fears, such as fears of dogs, spiders, or flying.
The hippocampus is the part of the brain that encodes threatening events into memories. Studies have shown that the hippocampus appears to be smaller in some people who were victims of child abuse or who served in military combat.
Research will determine what causes this reduction in size and what role it plays in the flashbacks, deficits in explicit memory, and fragmented memories of the traumatic event that are common in PTSD. For more on the role of the hippocampus in anxiety see the Science Direct site.