Introduction
Although the association between smoking tobacco and
psychosis (in particular, schizophrenia) has been acknowledged,
the reasons why people with psychosis are more
likely to smoke compared with the rest of the population
are still unclear. Several theories have been proposed,
many focusing on the idea of self-medication—ie, smoking
corrects a pharmacological abnormality (such as excessive
dopamine blockade induced by antipsychotics), counteracts
negative or cognitive symptoms of schizo phrenia, or
relieves boredom or distress. Little attention has been
directed towards the possibility that cigarette smoking
might increase risk for the disorder. This shortfall is
surprising, particularly in view of the large amount of
attention paid to the role of other substances of misuse
(notably cannabis and stimulants) in the aetiology of
psychotic illness.4–7 This discrepancy is exemplifi ed by two
meta-analyses: in the fi rst, 83 studies were included in
which the onset of psychosis and cannabis use was
analysed;8 in the second, ten studies investigated tobacco
use and onset of psychotic illness