Anxiety disorders have a complicated network of causes, including:
- environmental factors, such as stress from a personal relationship, job, school, finances, traumatic event, or even a shortage of oxygen in high-altitude areas
- genetics
- medical factors, such as the side effects of medicine, symptoms of a condition, or stress from a serious underlying medical condition
- brain chemistry
- use of or withdrawal from an illicit substance
Excessive anxiety is most commonly triggered by the stress of day-to-day living and any combination of the above. It is usually a response to outside forces, but it is possible that anxious feelings can emerge from a person telling himself or herself the worst will happen.
Anxiety can result from a combination of one or more of the above. For example, a person may respond to stress at work by drinking more alcohol or taking illicit substances, increasing anxiety.
Diagnosis
A mental health professional can diagnose anxiety and identify possible causes.
The physician will take a careful medical and personal history, perform a physical examination, and order laboratory tests if needed. These tests may provide useful information about a medical condition that may be causing anxiety symptoms.
To receive a diagnosis of generalized anxiety disorder (GAD), a person must:
- experience excessive worry and be anxious about several different events or activities on more days than not for at least six months
- find it difficult to control the worrying
- have at least three anxiety symptoms on more days than not in the last six months, including restlessness, fatigue, irritability, muscle tension, difficulty sleeping, and difficulty concentrating
Symptoms must interfere with daily living, causing absence from work or school.
If there is no specific cause for the anxiety and worry, a physician will diagnose GAD. In cases related to a clearer cause, a different diagnosis may be reached.
Source: https://www.medicalnewstoday.com/info/anxiety/what-causes-anxiety.php
Life and Psychology 