Schizophrenia is associated with a four-to-six-fold increase in violent behaviour but it is unclear whether it is schizophrenia itself or another factor associated with it that is behind the increased risk in violence. Researchers from Oxford University studied 88,028 people using data from Swedish registers of hospital admissions and criminal convictions from 1973-2006. The researchers found that among patients with schizophrenia 13.2% had committed at least one violent offence compared with only 5.3% of the general population. However, the rate of violence in people with schizophrenia and drug abuse was 27.6% compared to only 8.5% in those people who had schizophrenia but did not use drugs. After adjusting for other factors people with schizophrenia and drug problems were 4.4 times more likely to commit a violent offence while those with no drug problem were only 1.2 times as likely.
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