Anxiety disorder are a group of disorders (e.g. panic disorder, social and generalised anxiety disorder) that share emotions of excessive fear, anxiety and behavioural disturbances / Anxiety is mostly related to percieved future danger – in other words, fear of what is expected to happen, and may result in muscle tension and avoidance / Symptoms include: feeling nervous and tense, a sense of impending danger, struggling to sleep, struggling to control feelings of worrying, trouble with concentration, restlessness, pounding heart, rapid breathing, upset stomach, sweating, trembling, shortness of breath, feeling tired or weak, avoiding things that cause anxiety, panic attacks / Anxiety and depression are often linked / Anxiety can appear because of depression and depression can be triggered by an anxiety disorder.