焦虑意指由于情绪或心理上产生内在冲突，进而引发非理性的忧虑或恐惧感受。焦虑可能在特定情况下产生；也有可能是惯性或是常见与普遍的一种感受。焦虑通常与佛洛伊德对于压抑感受与冲动所提出的论点有关；此外，亦与习得或制约反应机制的概念相关。反应机制的概念提到，某些事件或刺激如果在过去曾经造成恐怖或紧张的经验，就会引发焦虑。

焦虑有很多形式，有社交方面的情绪焦虑，自我强迫，外伤后的压力，甚至是恐惧症。焦虑给身体带来极大负影响，例如，呼吸急促，头痛，心悸，四肢无力等等。焦虑的原因主要是外界环境所给与的惊吓与自身的抗压能力不能形成一定平衡。杏仁核和海马体是参与焦虑形成的神经部位。

Anxiety is an emotion characterized by an unpleasant state of inner turmoil, often accompanied by nervous behavior, such as pacing back and forth, somatic complaints, and rumination. It is the subjectively unpleasant feelings of dread over anticipated events, such as the feeling of imminent death. Anxiety is not the same as fear, which is a response to a real or perceived immediate threat, whereas anxiety is the expectation of future threat. Anxiety is a feeling of fear, uneasiness, and worry, usually generalized and unfocused as an overreaction to a situation that is only subjectively seen as menacing. It is often accompanied by muscular tension, restlessness, fatigue and problems in concentration. Anxiety can be appropriate, but when experienced regularly the individual may suffer from an anxiety disorder.