[tlarkworthy]

Well, its the same thing in prisons, so I always assumed its boredom/stress relief as the explanation for chain smoking.

[troygoode]

Or it indicates that prisons also contain many mentally ill inmates...

[bkmartin]

Which they do, but it is really tough to unwind the correlation/causation factors here.

[rabboRubble]

Err... you may have a significant overlap in the Venn diagram between prison population and people with schizophrenia. It's long known that mentally ill people make up a large part of the prison population.