Yeah there is something called ssri discontinuation syndrome...what is basically acute withdrawal lasts around 6 weeks but it can last for years as well in some people

SSRI discontinuation syndrome - Wikipedia, the free encyclopedia

So I'm wondering if he was being treated for social anxiety....if so dating or even regular interaction with other people may be not just difficult but actually unpleasant for him....it's something beyond being shy. Think of something that makes you nervous...snakes spiders etc...now imagine that someone told you that in order to get something you want like affection that you would have to endure a hundred of those things crawling on your skin....would you do it or would you simply choose to go without affection...

The withdrawal phase for a lot of drugs is worse than the condition was to start with so it's possible he'll be more comfortable over time but at the same time when you have severe social anxiety it's typically easier to avoid social interactions all together....sometimes therapy can be helpful with these conditions but a lot depends on the severity.