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According to the NIMH, the five major types of anxiety disorders are:

Generalized Anxiety Disorder (GAD) - Generalized Anxiety Disorder, GAD, is an anxiety disorder characterized by chronic anxiety, exaggerated worry and tension, even when there is little or nothing to provoke it. People with generalized anxiety disorder can't seem to shake their concerns. Their worries are accompanied by physical symptoms, especially fatigue, headaches, muscle tension, muscle aches, difficulty swallowing, trembling, twitching, irritability, sweating, and hot flashes.

Obsessive Compulsive Disorder (OCD) - Obsessive-Compulsive Disorder, OCD, is an anxiety disorder and is characterized by recurrent, unwanted thoughts (obsessions) and/or repetitive behaviors (compulsions). Repetitive behaviors such as handwashing, counting, checking, or cleaning are often performed with the hope of preventing obsessive thoughts or making them go away. Performing these so-called "rituals," however, provides only temporary relief, and not performing them markedly increases anxiety. People with OCD may be plagued by persistent, unwelcome thoughts or images, or by the urgent need to engage in certain rituals. They may be obsessed with germs or dirt, and wash their hands over and over. They may be filled with doubt and feel the need to check things repeatedly.

Panic Disorder - Panic disorder is an anxiety disorder and is characterized by unexpected and repeated episodes of intense fear accompanied by physical symptoms that may include chest pain, heart palpitations, shortness of breath, dizziness, or abdominal distress. People with panic disorder have feelings of terror that strike suddenly and repeatedly with no warning. During a panic attack, most likely your heart will pound and you may feel sweaty, weak, faint, or dizzy. Your hands may tingle or feel numb, and you might feel flushed or chilled. You may have nausea, chest pain or smothering sensations, a sense of unreality, or fear of impending doom or loss of control.

Post-Traumatic Stress Disorder (PTSD) - PTSD is an anxiety disorder that some people get after seeing or living through a dangerous event. When in danger, it’s natural to feel afraid. This fear triggers many split-second changes in the body to prepare to defend against the danger or to avoid it. This “fight-or-flight” response is a healthy reaction meant to protect a person from harm. But in PTSD, this reaction is changed or damaged. People who have PTSD may feel stressed or frightened even when they’re no longer in danger.

PTSD can cause many symptoms. These symptoms can be grouped into three categories:

1. Re-experiencing symptoms:

Flashbacks—reliving the trauma over and over, including physical symptoms like a racing heart or sweating
Bad dreams
Frightening thoughts.
Re-experiencing symptoms may cause problems in a person’s everyday routine. They can start from the person’s own thoughts and feelings. Words, objects, or situations that are reminders of the event can also trigger re-experiencing.

2. Avoidance symptoms:

Staying away from places, events, or objects that are reminders of the experience
Feeling emotionally numb
Feeling strong guilt, depression, or worry
Losing interest in activities that were enjoyable in the past
Having trouble remembering the dangerous event.
Things that remind a person of the traumatic event can trigger avoidance symptoms. These symptoms may cause a person to change his or her personal routine. For example, after a bad car accident, a person who usually drives may avoid driving or riding in a car.

3. Hyperarousal symptoms:

Being easily startled
Feeling tense or “on edge”
Having difficulty sleeping, and/or having angry outbursts.
Hyperarousal symptoms are usually constant, instead of being triggered by things that remind one of the traumatic event. They can make the person feel stressed and angry. These symptoms may make it hard to do daily tasks, such as sleeping, eating, or concentrating.

It’s natural to have some of these symptoms after a dangerous event. Sometimes people have very serious symptoms that go away after a few weeks. This is called acute stress disorder, or ASD. When the symptoms last more than a few weeks and become an ongoing problem, they might be PTSD. Some people with PTSD don’t show any symptoms for weeks or months.

Social Phobia (or Social Anxiety Disorder) - Social Phobia, or Social Anxiety Disorder, is an anxiety disorder characterized by overwhelming anxiety and excessive self-consciousness in everyday social situations. Social phobia can be limited to only one type of situation — such as a fear of speaking in formal or informal situations, or eating or drinking in front of others — or, in its most severe form, may be so broad that a person experiences symptoms almost anytime they are around other people. People with social phobia have a persistent, intense, and chronic fear of being watched and judged by others and being embarrassed or humiliated by their own actions. Their fear may be so severe that it interferes with work or school, and other ordinary activities. Physical symptoms often accompany the intense anxiety of social phobia and include blushing, profuse sweating, trembling, nausea, and difficulty talking.

WebMD also lists Specific Phobias - A specific phobia is an intense fear of a specific object or situation, such as snakes, heights, or flying. The level of fear usually is inappropriate to the situation and may cause the person to avoid common, everyday situations.