I have worked in many acute psychiatric units, and cannot help noticing that a large amount of coffee is consumed by psychotics and those with mental illness and personality disorders. On occasions when secure rooms containing coffee had been left unlocked and entered by patients I have even observed patients frenziedly eating coffee out of the jar, shovelling in one spoonful after another or tipping the jar up and gulping it down. 

Drug users and addicts of all kinds are generally addicted to coffee too, and I've noticed a large amount of coffee is also drunk by prisoners.  

I have not found the raw data to this study but they reveal it is small scale with the usual sampling - students. (Their own students are the favourite sample group of most social scientists.) Even so, I expect there is some truth in it.
https://www.dur.ac.uk/news/research/?itemno=7403

In myself I've noticed that coffee seems inclined to alter my mental channel and impinge upon clarity and steadiness, as if it has an interfering quality, which is partly why I prefer tea which does not have that effect. However, on one occasion when working in community health where emotionalism and coffee is God, I gave in to the urgings of my feminist-socialist colleagues and had a cup of their brewed coffee with them. For a while afterwards I could feel my brain firing erratically, had difficulty concentrating and thinking rationally. I even felt insecure, and stressed about nothing.

I have in my possession MRI scans of the brains of long term users of drugs of all types. The brains of long term heavy coffee drinkers and tobacco smokers are the most visibly obviously damaged, showing large areas of dead brain as a result of capillary breakdown. Of course, MRI scans don't show many forms of visibly subtle damage, and there are types of damage they can't display. But if you want holes in your brain then heavy smoking and coffee drinking might help you achieve that.