That so many schizophrenics smoke was actually established in a study published in 2006, but the figure has held up since then, even in the face of stiffer tobacco regulations and society in general backing away from it. There are a number of hypotheses that try to explain the link — personality, socioeconomic situation, etc — but Mark Stewart for the University of Michigan Risk Science Center writes that the patients may be smoking as a means of self-medication.
Schizophrenics often have auditory hallucinations, paranoia, delusions, and disorganized thinking. These symptoms are predominantly caused by the inability of the brains of schizophrenics to differentiate, sort, and focus on the multitude of stimuli that go on around us. Think of being in a busy restaurant. Imagine that instead of being able to block out all the noises, conversations, and movements around you, every single piece of sensory information is as important as the interesting things said by the attractive person sitting across from you. The effects of cigarette smoking and nicotine help schizophrenics through increased selective attention.
This is because, it's theorised, nicotine acts on the flow of dysfunctional flow of dopamine on a schizophrenic's brain. By correcting that, they may feel some relief from their symptoms. Unfortunately, all the adverse side-effects of smoking follow, resulting in higher rates of lung and heart disease.
But the relief a cigarette may provide, at least in the short term, could outweigh the effects of the many anti-psychotic drugs they take. Is there some kind of middle ground then? Nicotine is still a highly addictive substance, but is there a way to use it in treatment? [Risk Science Blog via BoingBoing]