Take him to a psychologist. Not because he has a disorder, but because he is highly intelligent and both you and he need to learn how to deal with this gift.

Your son needs peers who share his intelligence. I don't know where you live, but any psychologist worth the name knows of local organizations that help highly intelligent children socialize with other highly intelligent children and find for them the special teaching that they need. Where I live, there is a special school for highly intelligent children. If such a school does not exist, your son could skip some classes.

Everyone – no matter if they are alcoholics or gay or highly intelligent – is relieved once he finds others who are like him. That is the single most important experience for anyone who is "different". The fact that you can talk to someone who knows how you feel is healing in and of itself. And making friends and having people that are interested in the same things will make him happy.

Do not send him to the internet unsupervised. He might be highly intelligent, but he still lacks the experience and maturity to deal with some of the more dangerous aspects of the net. There are places where nihilistic people gather and encourage each other in their negativity. Some of this turns to crime, some to suicide or drugs. Despite his intelligence, your son probably needs some kind of social life, and the lack of adequate peers makes him vulnerable, and his negative attitude makes him even more vulnerable.

Even if life is ultimately meaningless (which I think it is), you can still have fun with it. My argument to your son's argument is:

> If you have two hours to live, why would you actively want to be miserable during those two hours? Purely from a logic point of view that seems like a stupid decision. You'll be dead long enough and there is no need to act dead before you die. Your body feels good if you provide it with tasty food. So quite obviously the fact that your body will eventually die, does not prevent it from experiencing pleasure. The same is true for the mind. All you need to do is find pleasant experiences for your mind. It is meaningless that life is meaningless.

Give him autobiographies of other gifted people. Or do an internet research and find adults alive today who had been gifted children. Some have had difficult lives, others have found happiness. Show your son the adults and how they are not unhappy but have found something to do with their talent. Maybe some example of what your son might make of his gift will give him a perspective.

But most of all you all seem to be completely overwhelmed by the situation and need to get some professional support to help you out of it. It is common that highly intelligent children are depressed, but they quickly become happy once they find the appropriate peers and a schooling that addresses their talents.

A psychologist will test your son and find out what his special talents and what his weaknesses are. With this understanding he will help you tackle the problem.

Good luck!

Please read the section "Social and emotional issues" in this Wikipedia article: https://en.wikipedia.org/wiki/Intellectual_giftedness