JOENSUU, Finland, June 4 (UPI) -- Painkillers and tranquilizing benzodiazepines, prescribed to patients for anxiety issues, have been linked to risk of homicide in the first study to consider the relationship between the medications and murderers.
The study, which looked at the prescription drug use of 959 people convicted of homicide in Finland between 1993 and 2011, also found that anti-depressant drugs were linked to only a slightly higher risk, contrary to common thought in both Finland and the United States.
In addition to use of these three types of drugs, researchers also considered the specific reason the drug had been prescribed and the effects of any additional intoxicants the person may have been using at the time of murder.
"I think that these chemical substances affect the impulse control of the person," Dr. Jari Tiihonen, a professor at the University of Eastern Finland told Medical Daily. "The only surprsing thing is that painkillers also increase the risk."
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The study found that use of anti-depressants increased the risk of homicide by 31 percent and use of benzodiazepines raised the risk by 45 percent. The largest increase in risk, however, was in people taking opiate painkillers at 95 percent and anti-inflammatory painkillers at 206 percent. Overall, people under the age of 26 were found to be at 223 percent greater risk to commit homicide if they were using opiate painkillers and 95 percent greater risk if they were on benzodiazepines. The median age of people in the study was 36.3 years old.
Within the 959 people who were considered in the study, researchers also found that 79.4 percent were under the influence of alcohol and 5.3 percent were under the influence of illicit drugs, as confirmed by police. Researchers couldn't say how much of an affect this had, however they acknowledge it must be considered when looking at the results of the study.
"Benzodiazepines can weaken impulse control, and earlier research has found that painkillers affect emotional processing. Caution in prescribing benzodiazepines and strong painkillers to people with a history of substance abuse is advisable," Tiihonen said in a press release.
The study is published in World Psychiatry.
