The excessive worry or anxiety associated with GAD occurs more days than not in at least a 6 month period. People with GAD find it difficult to prevent the anxiety from interfering with their daily activities. Many times the anxiety is irrational meaning that the probability of the anxiety-provoking event actually occurring is much lower than what the person expects. People with GAD experience a much higher level of anxiety than normal people. Adults with GAD usually have anxiety pertaining to normal everyday functions. Examples could include job performance, house or auto repairs, safety of children or family members, and finances.  
GAD is also associated with several symptoms which can include muscle tension, insomnia, fatigue, irritability, restlessness, and difficulty concentrating.

Obsessive-Compulsive Disorder (OCD) is marked by obsessions and/or compulsions that cause significant impairment in daily functioning, consume at least an hour of time each day, or both.  Sometimes, people with OCD have insight into their problem meaning that they are aware that their obsessions and/or compulsions are out of the ordinary.

Obsessions
Obsessions are classified as thoughts, ideas, images, or impulses that are considered intrusive and that cause distress or anxiety.  The most common types of obsessions are recurrent thoughts about ordering (the need to order or organize objects that are out of order), contamination (fear of becoming contaminated), and doubting ones actions (wondering if one has left the oven on or feeling they may have hurt someone).  Individuals with obsessions usually attempt to neutralize them with another thought or an action (i.e., a compulsion)
Compulsions
Compulsions are classified as repetitive behaviors or mental acts which attempt to alleviate anxiety.Compulsions are not an attempt to provide pleasure. Some of the most common compulsive behaviors are hand-washing, checking, and ordering. Some of the most common compulsive mental acts are praying, counting, and repeating words or sentences.
An example of someone with OCD might be one who consistently thinks that they might have left the oven on (obsession). In order to alleviate the anxiety related to leaving the oven on, they would have to continually check to make sure it is off (compulsion). Someone else could continually wash their hands (compulsion) in order to prevent possible contamination (obsession).

What is a Panic Attack? A Panic Attack can be described as an overwhelming feeling of fear in a brief period of time in the absence of real danger. Panic attacks often feel as if they “come out of the blue”. They can be unexpected or they can be caused by known fear-provoking situations (e.g., fear of heights, public speaking). Many times people that experience Panic Attacks end up going to the hospital because they feel they are having a heart attack. This is due to the similarity of some of the symptoms between Panic Attack and heart attack (accelerated heart rate, shortness of breath, and chest pain). Symptoms of a Panic Attack can include:

Nausea Feeling lightheaded  Fear of losing control  Fear of dying Trembling  Sweating

Shortness of breath  Accelerated heart rate  Feeling of choking  Chills or heat spells  Chest pain

The fundamental requirement for PTSD is the development of symptoms that are in sync with the disorder following a traumatic event.  The traumatic event had to have involved actual death, near-death experiences, threat to one’s physical integrity, or serious injury.  The person’s response to the traumatic event must have involved intense fear, feelings of helplessness, or horror.  Examples of traumatic events can include (this is not a complete list):

1. Military combat
2. Natural disasters
3. Violent personal assault
4. Automobile accident
5. Witnessing the death or serious injury of someone
6. Learning of an unexpected death of someone close

PTSD is also characterized by the reexperiencing of the traumatic event.  Recurrent thoughts, images, or dreams are just some of the ways that people with PTSD reexperience the traumatic event.  In most cases, people will start to reexperience the event within 3 months of the actual occurrence of the event.  PTSD can be accompanied by several different symptoms of heightened arousal:

1. Increased irritability
2. Sudden outbursts of anger
3. Difficulty falling asleep or staying asleep
4. Difficulty concentrating
5. Being easily startled

Another associated feature of PTSD is effort to avoid thoughts, feelings, or reminders of the traumatic event.  Some people with PTSD will seem detached from others, uninterested in significant activities, and will want to avoid discussing the event.  For example, someone who was involved in a war and witnessed a lot of killing may avoid being around other people in the military or may avoid watching any television programs about the military.  The feelings and thoughts can be so disturbing that avoidance of them altogether is not uncommon

Typical fears associated with Agoraphobia can consist of being in a crowded environment, traveling in an automobile, or being outside of the home alone.  Symptoms of Agoraphobia are usually panic-like symptoms or symptoms similar to a panic attack.  Agoraphobia can lead to chronic avoidance of situations that one may be afraid of.  People are often afraid of going to certain places fearing they will have a Panic Attack.  Chronic avoidance can lead to people staying inside of their homes for weeks, months, or even years at a time .

People with Social Phobia fear either performance situations, social events, or both.  In the case of performance situations, the fear stems from scrutiny of those watching or from concerns about embarrassment.  In the case of social situations, the fear stems from thinking that others will notice their social nervousness (shaking hands, quivering voice) and label them as “socially inept” or “stupid”.  
In most cases of Social Phobia, exposure to the feared situation will provoke anxiety or fear almost instantly.  The fear or anxiety in anticipation of the situation will sometimes cause a disturbance in the normal functioning of an individual.  The feared social event is usually avoided altogether although some people with Social Phobia are able to endure the situation with severe anxiety

Someone that has a Specific Phobia exhibits fear toward an object or situation and realizes that it is unreasonable. Someone that is fearful of being robbed that lives in a crime-ridden neighborhood would not be diagnosed as having a Specific Phobia because the fear is warranted.
Exposure to the feared object or situation will almost always cause an immediate response of fear or anxiety. The fear/anxiety can develop into a panic attackin severe cases.
What Causes a Specific Phobia?
There is usually a precipitating traumatic event that causes someone to develop a specific phobia.  For instance, someone who was involved in a severe automobile accident may develop a fear of driving afterward.  Someone who was attacked by a dog may have developed a phobia of dogs.  Sometimes a phobia can be developed by observing the circumstances of other people (a friend died in a plane crash which caused a phobia of flying in someone).  Listening or watching certain messages can also cause phobias (repeated news coverage on the dangers of carnival rides).