There are various reasons why Communication Anxiety occurs, and it is usually deep-rooted, going beyond a single event. We could categorize such communication anxiety into external factors and internal factors.
One example of external factors could be unfamiliarity. The unfamiliarity of occasion or audience can make speakers uncomfortable giving a speech in front of a big crowd. Also, the importance of situation may add some burden.
Internal factors are other reasons of Communication Anxiety. Many people have anxiety sensitivity, which is the fear of fear and magnifies apprehension. Although no one is perfect, perfectionism is another reason that pressures people as they dread making a mistake during the speech. Picturing your listeners as predators or faultfinders is referred to as audience misperceptions, and makes you nervous if you are worried for being evaluated. Lastly, the expectation of dire consequences that may happen after failing to give a good speech also causes communication anxiety.