Recent research has shown that anxiety disorders may develop from a complex set of risk factors, including genetics, brain chemistry, personality, and life events, the Anxiety and Depression Association of America reported. These disorders affect some 40 million adults in the United States, the ADAA reported.

What are Anxiety Disorders?

The broadest type of anxiety is called generalized anxiety disorder, but you’ve probably heard it called GAD. Symptoms include persistently having anxious thoughts on most days over a six-month period, fatigue, problems sleeping, and repeated panic attacks, according to the ADAA.

Anxiety disorders can also manifest themselves in a specific situation — like interacting with a group of people — or social anxiety. Other types include panic disorder, post-traumatic stress disorder, and specific phobias.

[Related: Normal Anxiety vs. Anxiety Disorder: Signs, Symptoms To Tell The Difference]

Genetics

Just like genetic risks of heart disease or cancer, anxiety disorders can actually run in families. Studies have shown that they can at least partly be inherited from one or both parents, according to WebMD.

DNA Genes

Life Events

Studies have shown that severe or long-lasting stress can physically impact the brain’s nerve cells. This interrupts circuits that transmit information from one region of the mind to another, WebMD reported.

Other research has revealed that people with certain anxiety disorders actually experience brain structure changes in certain areas that control memories linked with strong emotions.

Additionally, environmental factors like trauma could have the power to trigger an anxiety disorder in people who have an inherited susceptibility, despite not developing the disorder earlier.

[Related: Anxiety Disorders: 15 Facts About The Most Common Mental Disorder, From Symptoms To Efforts To Reduce Stigma]

So, What Caused It?

As scientists continue their research on mental illness, it is becoming clear that anxiety disorders are likely caused by a combination of factors, including changes in the brain and environmental stress.

(Originally published here on the Medical Daily website)