Having high levels of anxiety that disrupt daily life is considered an anxiety disorder. A patient can be diagnosed with one of the six major types of anxiety disorder: generalized anxiety disorder (GAD), obsessive-compulsive disorder (OCD), panic disorder, phobias, post-traumatic stress disorder (PTSD) and social anxiety disorder, according to HelpGuide. Anxiety disorders do not have just one cause---the patient will have a combination of multiple factors that culminate into the disorder.
Genetics
The National Alliance on Mental Illness (NAMI) states that children and adolescents have a higher risk of developing an anxiety disorder if a parent or caretaker has an anxiety disorder. The University of Maryland Medical Center adds that genetics is a possible cause of anxiety disorders by citing studies of twins; a person who has an identical twin with an anxiety disorder has a higher risk of developing than a person who has a fraternal twin with an anxiety disorder. A person with a family history of anxiety disorders may have an altered brain chemistry or brain function, which may predispose him to a disorder.
Medical Conditions
The Merck Manual Professional Edition states that certain medical conditions can trigger anxiety. Diseases that affect certain neurotransmitter and hormone levels can cause anxiety, as the neurotransmitters control the patient's mood. For example, hyperthyroidism results in the overproduction of hormones that influence mood. Pheochromocytoma and hyperadrenocorticism affect the adrenal gland; pheochromocytoma is an adrenal gland tumor that increases the release of epinephrine and norepinephrine, and hyperadrenocorticism results in the excessive production of cortisone. Heart problems, such as heart failure and arrhythmias, and breathing conditions, such as asthma and COPD, can also cause anxiety.
Traumatic Experience
Events that a person finds deeply disturbing can be one of the causes of an anxiety disorder. The University of Maryland Medical Center notes that certain anxiety disorders are triggered by trauma. For example, PTSD is the result of a traumatic experience, such as war, sexual assault or witnessing a murder. Early trauma can result in anxiety symptoms later in the patient's life. Social anxiety disorder and panic disorder also can be started by a stressful event, such as giving a presentation. Personality also plays a role in how a person is affected by a traumatic event. The Medical Center adds that a person with low self-esteem and poor coping skills is more affected. Therefore, one person may develop PTSD after an event, while another person in the same situation will not.
