Research is ongoing into the causes, diagnosis, prevention, and treatment of anxiety disorders and other mental illnesses.
Scientists are looking at what role genes play in the development of these disorders and are also investigating the effects of environmental factors such as pollution, physical and psychological stress, and diet.
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.
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 NIMH-sponsored 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.
Several parts of the brain are key actors in the production of fear and anxiety. 15 Using brain imaging technology and neurochemical techniques, scientists have diskovered 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.16, 17 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.
By learning more about how the brain creates fear and anxiety, scientists may be able to devise better treatments for anxiety disorders. For example, if specific neurotransmitters are found to play an important role in fear, drugs may be developed that will block them and decrease fear responses; if enough is learned about how the brain generates new cells throughout the lifecycle, it may be possible to stimulate the growth of new neurons in the hippocampus in people with PTSD.18