A quick Google search reveals that there are many people trawling web forums wanting to find out if there is a difference between high functioning autism and social anxiety. Some sites list it as one of their most frequently asked questions and the answer is always the same: autism and social anxiety are two very different things.
The key difference is the source of these symptoms. People with social anxiety do not lack the capability to interact with others but their fear of social situations causes considerable distress and can impair their ability to function. Their social skills are intact but they are too anxious or scared to put them into practice. This is marked by shortness of breath, shaking hands, blushing, etc.
Definitions of autism do not include fear of social interaction instead citing that those affected have problems understanding non-verbal communication and do not know the appropriate way to act. This does not mean they don’t want to make friends, but rather that they don’t know how. Some symptoms of autism can be marked by repetitive behavior, obsessive preoccupation with certain objects, abnormal focusing skills, etc.
It is easy to understand why the two are often confused as they have many symptoms in common. People with these conditions can be shy, avoid eye contact, be awkward in social situations and have bad communication skills.
Another difference is that social anxiety is not permanent – it can appear and be cured later in life, or come and go at different stages. Autism is a complex, lifelong disorder that is generally improved through behavioral therapies.
Many autistic people are not afraid of social interaction at all. Autism and social phobia can occur together, but they are completely different things.
For a complete list of autism symptoms, please visit our website here: http://www.icare4autism.org/what-is-autism/overview/
For more information on behavioral therapies, you can read here: http://www.icare4autism.org/what-is-autism/treatments/