Hi Parent :)
Thank you for sharing your post! I completely agree with what Summer Rose and mick90 said about things that can help with anxiety and depression - CBT is definitely an option that really helps and works for so many people, including myself.
I'm sorry to hear that your son has been struggling for some time :( Having both social anxiety and depression myself, I completely understand how he must feel, and how hard it is to be motivated when you are so weighed down by your own thoughts, so I'd thought I'd share what has helped me the most, in hope that it can help him too :)
This may sound silly or obvious, but more often than not, the best thing for someone to do (and for me to do) when their depression really hits hard is to actually be with other people, when all they want to do it be alone. I find that this is a great way for me to be around the people I love ad feel comfortable wit, who I know will boost my mood and make me feel better. Like mick90 said, exercising is another really good way to handle mental illness, and I have found is be helpful in managing my depression.
In regards to social anxiety, it is difficult to overcome, but CBT and 'exposure' therapy is very effective in treating social anxiety, as it continually exposes the person to the situations that make them anxious, and over time, their anxiety will decrease. I know that depression and social anxiety plays a huge role in the interference of sleep (particularly social anxiety), and from personal experience, sometimes makes it nearly impossible to sleep and silence the thoughts and social worries. I have found medication to be extremely helpful in managing this and improving my sleep, as well as improving my social anxiety and depression dramatically - along with CBT, it has personally been the most effective treatment for my mental health.
With that being said, medication may not be the best treatment for your son, and like Summer Rose said, CBT may not be either, however it has been such a positive turning point in so many people's lives when dealing with their mental health. There are so many other treatments available that may also help your son, but it is important to remind him to be kind to himself and know that he is never alone.
Hope this was helpful :)
Take care - hope you're well xx