Two points:

People with head problems frequently (not always) self-medicate. Their illness causes pain and discomfort. As human beings, they try to resolve that pain and discomfort in whatever way they can. So, frequently (not always) they use things like alcohol, nicotine, caffeine or whatever to feel better. So far as I know no one is yet in a position to say that it's proven that these substances DO NOT alleviate symptoms of some head problems. They may well do so. And it is true that, statistically, a larger percentage of people with head problems smoke cigarettes than the general population.

For all we know at present, the comforts provided to people with head problems by nicotine, caffeine and alcohol aren't illusory, are not limited to the simple fulfillment of an addictive need. They may well provide benefits above and beyond the other benefits that can easily be obtained by such sufferers. It would be very valuable indeed to have solid answers to all of these issues. I'd hope that NIDA is funding projects for such knowledge right now. But as things stand at present, I don't think we can easily dismiss the analgesic properties of these substances for people with head problems.