Psychological problems will be the worst ones to deal with for people leaving in confined space.
Yet Musk wants to send just anyone
Although to be fair, he does admit that they may not survive.
As I and others have said earlier, Musk is just very good at marketing communication. All he wants is to get on with his projects. He probably only means one tenth of what he says.
When it comes to space travels, and particularly sending people to Mars, to get the most people on board with this, communication IS key. Anyone with half a brain can figure out that this will cost so much money per capita, and will require heavy training and rigorous selection no matter how sophisticated technology we eventually use, that only an extremely small fraction of the population will be able to be part of it, if it ever happens. But this makes it an essentially elitist project, which can only encounter a lot of resistance if you want to present all this as democratizing space travel. So to make it look more "inclusive", you'll just pretend that anyone will be able to go. That's really basic marketing.
Just my 2 cents. I know some people prefer thinking that Musk is just a delusional nutcase. It's probably more comfortable to think he lies to himself, rather than to the whole world.
Do I fully blame him? What he does is not my thing, but I admit he has achieved a whole lot, even if he hasn't achieved everything that he has ever claimed he would.
Wouldn't surprise me if psychological issues become the biggest problem.
One of the numerous problems probably. The other problem is, no human has ever been subjected to life in non-earth-like conditions for more than a few months (in the ISS), so I'm sure we can also expect a lot of health issues, unless we can reproduce a very earth-like environment elsewhere, which is sort of doubtful. It's likely that if anything, we will barely manage to build environments that are good enough for survival and what would happen after a few years, I guess nobody knows.