Anxiety disorders are a group of conditions where people experience intense anxiety or fear with persistent desire to avoid the anxiety provoking triggers. Depending on different triggering situations different types of anxiety disorders are:

• Generalized anxiety disorder is a condition where person experiences unremitting worry about  different things such as health, finances, family, work and find it extremely hard to relax.
• Panic disorder is characterised by repeated anxiety attacks which appear “out of blue” along with fear of having more panic attacks. 
• Agoraphobia is fear of places where escape may be difficult such as crowds, markets, trains etc. People can have both Panic disorder and agoraphobia.
• Social phobia is a condition where a person is terrified of social situations and avoids them due to the fear of embarrassment or being judged 
• Separation anxiety disorder is a conditions seen in children or teenagers who experience intense anxiety when they are separated from their parents even for short periods. These individuals try everything to prevent separation and often come across as “clingy”.
• Specific phobias are a group of conditions where  people experience unreasonable fear or avoidance of specific animals, insects, heights, flying, enclosed spaces, water, blood, etc.
• Obsessive compulsive disorder (OCD) is a condition where the person has repeated unpleasant thoughts or urges (obsessions) such as feeling their hand are dirty or need to count or arrange things. At the same time they engage in repeated behaviour aimed at neutralising this fears (compulsions), such as washing hands or counting things, etc.  OCD is diagnosed when these thoughts and behaviour become too distressing and excessive.
• Body dysmorphic disorder is a condition  where a person becomes excessively concerned  about minor defects in appearance and engages in behaviour to conceal the blemish with makeup or sometimes cosmetic surgery.
• Hoarding disorder is a condition where a person collects or buys unneccesary household items creating a squalor and experiences intensely anxious when they have to part with or discard their possessions. 
• Post-traumatic stress disorder (PTSD) is a condition that can develop after exposure to  traumatic event such as war, natural disaster, motor accident, physical or sexual assault. Symptoms includes: nightmares, flashbacks, hypervigilance, avoidance,  dissociation or numbness.

When someone is under a lot of stress their bodies release a chemical adrenaline in the blood which causes symptoms such as palpitation, muscle tension, racing thoughts, dry mouth, dizziness, feeling of choking, butterflies in stomach, etc. These symptoms constitute what is known as Flight or Fight reaction of Stress. These symptoms disappear when the stress is over. It appears that brains of individuals with Anxiety disorders fire away repeatedly causing unrelenting stress reaction. Another explanation is that their anxiety is maintained due to their severe avoidance which does not allow disconfirmation of their  beliefs about overestimation of risk.