Memory reconsolidation as a possible treatment for sad.
I recommend you to watch the video 'memory hackers' (just type Memory hackers on youtube, is a documentary with more than 1 hours in duration).
This video is a documentary about Memory reconsolidation ( a new discovery in neuroscience made in 2017), Memory reconsolidation is a processes that is used to modify memories in the brain, it can even be used to modify or remove fear memories in the brain (as shown in the video, in case of man who had archnofobia and by using the process of Memory reconsolidation, in two months, he was able to lose his fear of spiders). I believe that this process can be used to fix sa disorder by reducing or even removing the fears of social situations, and thus letting the brain to be calm and able to function normaly in social situations.
Another thing that I think it may be helpful is the book ' evolve your brain' by doctor Joe Dispensa, in this book he teaches a way to train your brain to feel less fear and anxiety. You can download it for free in torrent websites like extratorrents, or pdf download sites like pdf drive.