Scientists find no link between antidepressants and homicidal behaviour
Certain medications that affect the central nervous system can lead to an increased risk of committing homicide but antidepressants are not among them, shows new study.
Not long after this year’s tragic Germanwings plane crash in the French Alps, the media's attention turned to the pilot’s state of mental health and his prescribed medication.
Numerous reports in the mainstream media linked his depression and even the prescribed antidepressants to the act of mass murder whilst an equal number of articles and social media content decried the link made between the two.
The same reactions have been seen in the wake of massacres in USA and Finland perpetrated by young people prescribed antidepressants.
In amongst all this controversy, is there any evidence to suggest that the psychotropic drugs prescribed to perpetrators of homicide in any way influenced the risk of such an event?
The answer according to a new study is no – instead it is other prescribed medications that can increase the risk of committing murder.
In a new Swedish-Finnish study published this week in the scientific journal World Psychiatry, scientists report that certain painkillers and regularly prescribed sedatives that affect the central nervous system and are known to affect emotional processing and impulse control, can indeed lead to a substantially increased risk of committing acts of homicide based on a large group of convicted offenders.
The risk from antidepressants was much smaller, and contrary to popular belief, was not indicative of a substantially increased risk of homicide.
Highest risk from painkillers
A team of scientists lead by Jari Tiihonen of the Department of Clinical Neuroscience, Karolinska Institute in Stockholm, studied 959 cases of criminals convicted of homicide in Finland between 2003 and 2011.
They obtained records of all prescription drugs prescribed to the perpetrators before they committed their crime.
“We studied all homicide offenders in Finland over a ten year period and used a prescription database to find out what medication the offenders had used before and during the crime,” says Tiihonen.
“We assessed whether had they had taken medication previously or just before they committed homicide or if they’d been taking the medication regularly for a long time, and we assessed the impact of many other confounding factors,” he says.
First, Tiihonen and his team assessed the risk of committing murder according to whether the offenders were or were not using drugs from three major categories of psychotropic medications: antidepressants, benzodiazepines (sedatives used to treat anxiety and insomnia), and antipsychotics.
Next, they looked at a second group of medications which included common prescription painkillers. These were opiate painkillers used to treat severe or long-term chronic pain such as codeine and morphine and so-called non-opiates, the anti-inflammatory painkillers such as aspirin or ibuprofen. They assessed the risk factors amongst this group associated with each of the prescribed medicines.
“We saw that homicide was not associated with a significant increase in the use of antidepressants, but that there was a substantially increased risk in use of benzodiazepines and especially so from painkillers,” says Tiihonen.
In fact, the risk of committing murder was more than doubled in those using painkillers, up by 206 per cent when compared to homicide offenders not taking the prescribed medicine. This was highest in young offenders, reaching 224 per cent.
First nationwide study of its kind
According to Marieke Liem, chair of the European Homicide Reach Group and researcher at Centre for Terrorism and Counterterrorism in the Netherlands, this is the first study to assess the risk of violent behaviour across an entire nation and by using such a large range of drugs.
“Other studies focus on a particular type of medication or non-prescription drug. They may, for example, assess the extent to which the use of that particular drug is related to certain types of violence but not with the range of drugs that we see in this new study,” says Liem.
“These studies are usually also limited to a small number of offenders, and crucially, none of them have looked at the issue on a nationwide scale,” she explains.
“This makes the statistical basis of the conclusions [of the new study] very strong,” says Liem. “It’s very important research – the first of its kind in the world.”
Doctors should not be swayed by unproven popular beliefs
The advice for doctors is clear.
“This is the first time that we can say the risk of committing murder associated with psychotropic drugs like antidepressants is not dangerous, and so doctors should not withhold these medications from people who need them,” says Tiihonen.
Liem echoes this sentiment, stressing that whilst the media can be quick to jump to conclusions about antidepressants and make links to homicidal acts, it needs to be judged scientifically.
There has been a lot of discussion about whether these drugs impact on homicide, but according to Tiihonene and his team, it seems that none are as dangerous as painkillers, which are known to affect emotional processing, and benzodiazepines, which can weaken impulse control.
Tiihonene advises caution in prescribing these to people with a history of substance abuse.
Only possible in Scandinavia
Liem doubts this research could be repeated in countries outside of Scandinavia where medical records are either not as comprehensive or where there are greater restrictions on access to criminal and medical records.
“In Scandinavia everyone is routinely tracked from birth via national registers and these are available for researchers. Elsewhere, the registers are either not as comprehensive, like in the USA, or their use is particularly restricted by privacy legislation, which is the case throughout much of Western Europe. Scandinavia really is an exception,” she says.
Good access to these national records was crucial in being able to conduct a case-controlled study in this new research. For example, for each offender, the scientists looked at ten others with similar demographics so that they could avoid biasing people from any particular socio-demographic background.
