Panic disorder is where you have recurring and regular panic attacks, often for no obvious reason. It is a perfectly natural response to feel anxious when you are in danger or in a stressful situation but people with panic disorder experience feelings of anxiety, stress and panic regularly and at any time. Panic affects your body, your mind and the way you behave. When someone has a panic attack they may think that they are dying, suffocating or having a heart attack because the physical symptoms can feel similar, such as tightening of the chest or difficulty breathing. Although panic attacks can often be frightening, they don't cause any physical harm. People who have had panic disorder for some time usually learn to recognise and control their symptoms. When panic occurs, it is very distressing and frightening for the person affected. It is very common for a person to feel quite at ease one minute and then be struck by utter terror the next. Panic can happen without warning and it can make people feel very vulnerable.
Read the NHS self-help guide to Panic.