Both mental illness and the use of psychiatric drugs have been blamed for violent behaviors, but the scientific evidence for a connection is limited. Now, a new study suggests that taking not only tranquilizers but also regular prescription pain relievers is linked with an increased risk of committing homicide.
Researchers in Europe found that people who were on certain medications were at greatest risk of killing someone, compared with people who were not using these medicines. The high-risk drugs include benzodiazepines, a class of tranquilizers used to treat anxiety, insomnia and panic disorders, as well as pain relievers, such as opioid medications and anti-inflammatories,
The results also showed that people taking antidepressants had only a slight increase in homicide risk compared with people taking other medications involved in the analysis, even after the researchers took into account factors such as mental illness. The study was published online today (June 1) in the journal World Psychiatry.
The researchers looked at data collected from about 960 men and women in Finland, ages 13 to 88, who were all convicted of homicide. For a control group, the researchers matched each person who committed homicide with 10 other people who had not committed homicide but were the same age and gender, and lived in the same town.
The researchers then searched a nationwide drug registry, looking at whether the people in the study had used psychiatric drugs, as well as medications that relieve pain, manage epilepsy and control addictions, over a seven-year period. The researchers also reviewed police reports to check whether the criminals were considered drunk or high at the time of these murders.
The findings showed that tranquilizers increased the risk of committing a homicide by 45 percent and antidepressant use increased the risk by 31 percent.
The researchers were surprised to find that the use of anti-inflammatory pain relievers was tied to an increase of more than 200 percent in the risk of committing homicide, while opioid pain relievers elevated risk by 92 percent, Tiihonen said.
The researchers speculate that tranquilizers may weaken people's impulse control. Other studies have suggested that using certain painkillers may dull mechanisms responsible for processing emotions.
Two thirds of people who died by probable suicide were not taking the psychiatric medication which had been prescribed for them at the time, a new study has revealed.
The findings have emerged in the post-mortem reports of 153 people who took their lives in the west of Ireland between January 2006 and 2012.
Failure to take antidepressants and antipsychotic medication prior to death by suicide has also been found in other international studies, particularly in people suffering from schizophrenia.
The findings will add to the debate over the "black box" warning on antidepressant medication.
This is a warning saying they could increase the risks of suicidal thinking and behaviour in young people, which was placed by the medicines' watchdog in the United States in 2004.
But the drop in use was followed by a 22pc increase in suicide attempts among teenagers and a 34pc increase among young adults, according to a previous study of millions of young people.
In this latest Irish study, led by researchers at the Department of Psychiatry in NUI Galway, just one person who suffered from schizophrenia had antipsychotic medication detected in their toxicology report.
"It is possible that some individuals had their treatment stopped by a health professional outside the mental health services rather than discontinuing the medication themselves," said the authors in the report, published in the 'Irish Journal of Psychological Medicine'.
Previous studies have also shown that mental health patients who do not take their medication are at higher risk of suicidal thoughts or taking their own lives.
Commenting on the findings, Mater Hospital psychiatrist Professor Patricia Casey said the most telling aspects of the study were the toxicology results.
"In light of the antipathy to medication for the treatment of mental illness, and in particular to antidepressants, it is reasonable to question whether these cultural attitudes influenced the decision to discontinue treatment among the individuals evaluated in this study," she writes in her column in 'Health and Living' today.
If this could be tested by further research, it would make an important contribution to the so-called "black-box debate", she said.
Prof Casey asked: "Is non-treatment adherence and ultimately suicide an unintended consequence of the warning? This question cries out for an answer as life itself is at stake."
The west of Ireland study found that 57 had previously attended mental health services.
Nearly half of this group had depressive illness, followed by alcohol dependence or misuse. The remainder had diagnoses including schizophrenia, bipolar disorder and anxiety disorders.
Some 65pc had made a previous suicide attempt and 25pc had self-harmed without intent to end life.
There were four times more men than women among the tragedies. One quarter had been sexually abused as children..