People with social phobia will generally be even more afraid of public speaking as they would then be the centre of attention and could not hide as they would normally. However the fear of public speaking is much more common than full-on social phobia. Many people who can interact very easily one-on-one are still afraid of speaking to a group.
This is an increasing problem because group presentations are now a normal part of education in schools, colleges and universities. Speaking to a group is also increasingly required in the workplace, including in the Armed Forces. Giving presentations and talks is especially required at higher levels in an organisation, so the fear of this puts many people off applying for promotion.
I’ve written HERE about Social Phobia, and most of that applies also to the fear of public speaking, which is really a form of social phobia specific to situations where you are the focus of attention. However in the public speaking situation there are some additional factors.
For instance, in a large audience there will generally be some people who don’t seem to be listening, others who appear expressionless, others may look puzzled or amused. The anxious person’s imagination goes into overdrive when they notice these people. You may assume that the person who isn’t listening is bored or exasperated by your presentation, that the expressionless person is judging you coldly and severely, that the puzzled person is puzzled because you’re talking nonsense, and that the smiling person thinks you’re ridiculous.
Another factor nowadays is that presentations often involve pointing at a whiteboard or screen, which draws attention to your hand if it is shaking due to anxiety.
There is also the effect of breathing. Anxious people tend to speak faster, and therefore breathe faster and less deeply, using only the upper part of the lungs instead of the whole lungs. This can make you feel light-headed and unwell, like the start of a panic attack.
For this reason, whereas in most phobias the aim is simply to feel calm and act naturally, in the case of public speaking it is necessary to prepare yourself and rehearse your speech, even if you have no anxiety at all. This is because it’s difficult to estimate how much time is passing, so you need to ensure that your speech can fit easily into the time allotted without needing to talk faster than what feels comfortable for you.
You can read more background information HERE about how phobias develop.
And see HERE for more about how therapy for phobias works.