Stress can come from any situation or thought that makes you feel frustrated, angry, or anxious. What is stressful to one person is not necessarily stressful to another.

Anxiety is a feeling of apprehension or fear. The source of this uneasiness is not always known or recognized, which can add to the distress you feel.

Stress is a normal part of life. In small quantities, stress is good -- it can motivate you and help you be more productive. However, too much stress, or a strong response to stress, is harmful. It can set you up for general poor health as well as specific physical or psychological illnesses like infection, heart disease, or depression. Persistent and unrelenting stress often leads to anxiety and unhealthy behaviors like overeating and abuse of alcohol or drugs.

Emotional states like grief or depression and health conditions like an overactive thyroid, low blood sugar, or heart attack can also cause stress.

Anxiety is often accompanied by physical symptoms, including:

• Twitching or trembling
• Muscle tension, headaches
• Sweating
• Dry mouth, difficulty swallowing
• Abdominal pain (may be the only symptom of stress, especially in a child)

Sometimes other symptoms accompany anxiety:

• Dizziness
• Rapid or irregular heart rate
• Rapid breathing
• Diarrhea or frequent need to urinate
• Fatigue
• Irritability, including loss of your temper
• Sleeping difficulties and nightmares
• Decreased concentration
• Sexual problems

Anxiety disorders are a group of psychiatric conditions that involve excessive anxiety. They include generalized anxiety disorder, specific phobias, obsessive-compulsive disorder, and social phobia.

Certain drugs, both recreational and medicinal, can lead to symptoms of anxiety due to either side effects or withdrawal from the drug. Such drugs include caffeine, alcohol, nicotine, cold remedies, decongestants, bronchodilators for asthma, tricyclic antidepressants, cocaine, amphetamines, diet pills, ADHD medications, and thyroid medications.

A poor diet can also contribute to stress or anxiety -- for example, low levels of vitamin B-12. Performance anxiety is related to specific situations, like taking a test or making a presentation in public. Posttraumatic stress disorder (PTSD) develops after a traumatic event like war, physical or sexual assault, or a natural disaster.

In very rare cases, a tumor of the adrenal gland (pheochromocytoma ) may be the cause of anxiety. The symptoms are caused by an overproduction of hormones responsible for the feelings of anxiety.

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White KS, Farrell AD. Anxiety and Psychosocial Stress as Predictors of Headache and Abdominal Pain in Urban Early Adolescents. J Pediatr Psychol. 2005.

Lubit R, Rovine D, Defrancisci L, Eth S. Impact of trauma on children. J Psychiatr Pract. 2003; 9(2): 128-138.