This study further explores the association between schizophrenia
and caffeine use by combining the two prior published Spanish samples
(250 schizophrenia outpatients and 290 controls) with two additional
Spanish samples of long-term inpatients from the same hospital: 145
with schizophrenia and 64 with other SMIs sharing similar environmental
influences including psychiatric medications. The specific aims
were to establish, after controlling for confounders including tobacco
smoking, whether or not the association between schizophrenia and
caffeine is consistent across schizophrenia samples and across different
operational definitions of caffeine use (using versus not using caffeine,
high intake in caffeine users and total daily caffeine consumption in
caffeine users).