We categorize the symptoms of anxiety according to certain specific features and this tends to affect the way we approach and treat them. There is however considerable overlap in the symptoms of the anxiety disorders and this is because the most common feature of them all is anxiety.
If we look across the board, that is, from phobias, panic, GAD, OCD, health anxiety and PTSD, eight symptoms are characteristic of them all:
Avoidance: anything that makes us feel uncomfortable tends to be something to try and avoid. This fight-or-flight mechanism kicks in when we encounter situations or objects that cause anxiety arousal.
Physical arousal: is all part of fight-or-flight. The body switches into its action settings and as a result we feel the associated sensations of increased pulse and breathing rates, tingling in the hands and feet and sweating. If our anxiety is very pronounced we can experience difficulties in breathing, knots in the stomach, nausea, dizziness and even visual disturbances.
Intrusive thoughts: these are constant reminders of the issues that cause anxiety and embarrassment. In most anxiety disorders they lead to a kind of predictive anxiety, where the person is certain they won't cope. In OCD the thoughts can be highly distressing.
Vigilance: people with anxiety are often highly tuned to their environment and become very alert to circumstances that may cause them to feel anxious or may threaten their escape or avoidance of anxiety provoking situations.
Safety seeking: people with anxiety often adopt behaviors that help them cope. They may, for example, never go out unless they are with a partner. They may avoid eye contact to reduce the chance of social interaction or they may ask a lot of questions in order to avoid focus on themselves. These may provide temporary relief but they are a constant reminder to the person that the situation is unsafe and they have to do something to cope with it.
Threat estimation: two of the most common features of anxiety are the over-estimation of threat and the under-estimation of being able to cope.
Worry: even when away from situations that provoke anxiety, the anxious person may spend a lot of time reflecting on and worrying about past and future situations. Typically various 'what if' scenarios occupy their thoughts.
Low mood: anxiety can be an exhausting thing to live with. Anxiety and depression are commonly related but even if the symptoms of depression are sub-clinical, the person with anxiety will often experience low moods because they feel drained of confidence and see no particular relief in the future.