Drugs such as benzodiazepines and painkillers have been linked to an increased risk of committing a homicide.
The highest homicide risk was recorded in the use of benzodiazepines and painkillers, said a new study published in the journal World Psychiatry. The study analyzed the pre-crime use of prescription drugs among those convicted of a homicide in Finland between 2003 and 2011.
The study also shows the use of certain drugs that affect the central nervous system might be associated with this increased homicide risk. On the other hand, anti-depressants were associated only with a slightly elevated risk of committing a homicide.
Benzodiazepines have a 45 percent elevated risk of committing homicides, said the study led by Professor Jari Tiihonen at Karolinska Institutet's Department of Clinical. Opiate painkillers have a 92 percent elevated risk while anti-inflammatory painkillers have a 206 percent risk.
An increase in risk by 100 percent doubles the overall risk, said the study.
Antidepressants were associated with a 31 percent higher risk of committing homicides.
Benzodiazepines are antidepressants used to treat anxiety and insomnia. Benzodiazepines are generally seen as safe and effective for short-term use. Long-term use is controversial due to concerns about adverse psychological and physical effects, decreasing effectiveness, physical dependence and withdrawal.
The study revealed the median age of offenders was 36.3 years and that 88 percent were males. Less than four percent had more than one victim and five percent had taken an illicit drug. Researchers said the differences between drug groups could not be explained away by simultaneous use of alcohol or other drugs despite the high use of intoxicants.
The study adds more invaluable data to the debate over whether psychotropic drugs, especially anti-depressants, can cause violent behavior. This debate has been fuelled by massacres committed by young persons in schools and other public places in the US and other countries.
To investigate this claimed link between certain drug use and crime, the international research team, led by Professor Jari Tiihonen at Karolinska Institutet's Department of Clinical Neuroscience, analyzed the use of prescription drugs by 959 persons convicted of a homicide in Finland during 2003 to 2011.
After confounding factors were controlled for, the results showed the use of anti-psychotics was not associated with a significantly increased risk of committing a homicide, but the use of benzodiazepines was associated with a significantly elevated risk.
The study also found the highest risk of committing a homicide was associated with opiate painkillers and anti-inflammatory painkillers.
"In many cases, benzodiazepines had been prescribed in very high doses and for a long period of time", said Dr Tiihonen.
"Benzodiazepines can weaken impulse control, and earlier research has found that painkillers affect emotional processing. Caution is advisable in prescribing benzodiazepines and strong painkillers to people with a history of substance abuse".
The study was carried out in collaboration between Karolinska Institutet and the University of Eastern Finland, Niuvanniemi Hospital, the National Institute for Health and Welfare, the National Research Institute of Legal Policy, Kuopio University Hospital, Helsinki University Hospital, the University of Helsinki, the Kela Research Department, and Epid Research Ltd.