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Are antidepressants and painkillers playing a part in mass shootings?

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It’s often discovered afterward that mass murderers and shooters were taking psychiatric medication, and especially antidepressants like an SSRI (selective serotonin reuptake inhibitor) – but a new review suspects that even non-prescription painkillers, such as acetaminophen, aspirin and ibuprofen, could be having an effect on their behavior. In an “alarming discovery,” researchers say the drugs are distorting people’s feelings and making them less empathetic to the pain of others.

Researchers at the University of California, Santa Barbara (UCSB), say that drug regulators may need to start monitoring the psychological effects of painkillers – and the public should also be made aware that these over-the-counter medications do far more than just deaden pain.1

Following the recent mass shooting in a Florida school, in which 17 students and staff were killed, the focus has shifted to the mental state of such murderers, and especially the drugs they were taking. Nikolas Cruz, the Florida shooter, had been on antipsychotics to help him cope with his mental fragility, the Miami Herald reported.

These investigations have been fueled, in part, by studies that consistently link mass shootings to SSRIs. One found that healthy adults taking an SSRI were nearly twice as likely to consider committing suicide or violence,2 while another confirmed that someone taking an SSRI was nearly 50 percent more likely to be convicted of a violent crime.3

Killing the pain

But there could be another family of drugs that everyone should be looking at as well. Over-the-counter (non-prescription) painkillers – household names such as ibuprofen, acetaminophen, codeine and aspirin – that are consumed by millions every day for niggling pains and headaches could be changing the way we think, feel and see the world, researchers are discovering.

A research team from the University of East Finland investigated the drug-taking history of 959 people who had been convicted of homicide between 2003 and 2011 in Finland and compared them to over 9,000 people who had not offended. Fully expecting to find a close association with an antipsychotic or SSRI, the researchers instead found a far stronger connection with opioid painkillers, such as codeine, and non-opioids, such as acetaminophen and aspirin.

The link was even stronger among offenders who were under the age of 25; for them, opioid painkillers were the only drug that seemed to have an effect, even if they were also taking an SSRI.

Overall, taking an SSRI was associated with a 30 percent increased risk of offending, while taking a benzodiazepine drug like Xanax was linked to a 45 percent increased risk – but this was dwarfed by the effects of painkillers, which more than doubled the likelihood of homicide.

“Antidepressant use per se was associated with an only modestly increased risk of committing a homicide… and analgesic use was linked with a higher risk of homicidal offending,” the researchers said.4

No empathy

Along with opioids, researchers are also worried about the effects of acetaminophen (known as paracetamol in Europe). Around 52 million Americans take this painkiller every week, but the drug could be doing far more than just deadening pain – it may be deadening our feelings toward others.

Researchers from Ohio State University tested the drug on a group of 80 college students. Half were given 1,000 mg acetaminophen and the rest were given a placebo, or inert substance. After an hour, the participants read accounts of physical or social pain, and were asked to rate the level of pain being felt by the protagonists in the stories.

Those in the acetaminophen group all gave a lower pain score than those in the placebo group. A second experiment in another group of 114 students, this time involving loud and sharp noises, achieved similar results, with the acetaminophen group reacting less. Although acetaminophen may help deaden our feelings of pain, it may also deaden our empathy, or ability to relate to the pain of others, the researchers concluded.5

It’s in the brain

Research into the psychological effects of painkillers is thin on the ground – and, more surprisingly, so are studies that look at the possible role of SSRI antidepressants as catalysts for mass shootings – but the little that does exist started around 18 years ago.

In the early 2000s, researchers discovered that there is an overlap in areas of the brain that perceive pain and unrelated emotions such as fairness and social exclusion.

In a simple experiment, volunteers took part in a computerized catch game, and were told their partner was another person when, in fact, it was a computer. When the computer stopped throwing the ball, there was greater activity in an area of the participants’ brains known as the dorsal anterior cingulate cortex (dACC), which is usually associated with pain – but, in the experiment, the dACC was being activated by a sense of exclusion and unfairness because something, quite literally, wasn’t playing ball.6

This discovery opened the door to research into the possibility of painkillers being used to blunt feelings of social rejection. In one experiment, participants were given a 500-mg dose of acetaminophen or a placebo for three weeks, by the end of which, those taking the painkillers were reporting fewer instances of hurt feelings from a series of psychological tests compared with those given the placebo.7

A second experiment tested the effects of acetaminophen on feelings of social exclusion or inclusion, but this time by monitoring the dACC region of the brain during the tests. Again, activity in the brain
was dampened down among those taking painkillers.

All of this may have been seen as a positive breakthrough – it gives psychiatrists a new tool in helping sensitive people cope with the world, for instance – but it comes with consequences, the UCSB researchers point out.

Going deeper

The impact of painkillers on psychological processes hinges on the role of the dACC region in the brain. Although it’s generally considered to be involved in the perception of pain, the dACC’s real function may be subtler and related to any conflict in information processing. Pain could be one example, because it isn’t supposed to happen and is a clash b
etween a desired state and reality – a phenomenon psychologists call ‘cognitive dissonance’ – but it
could be any situation that is unexpected or different.

In one test, participants taking 1,000 mg acetaminophen reacted less strongly to thoughts of their own death than others given a placebo. In another, those on the painkiller didn’t respond to an absurd and illogical film they were watching. Another experiment found that acetaminophen blunted positive reactions toward a social group.8

Although most of the tests have used acetaminophen, the researchers suspect that similar responses could be seen when people use ibuprofen (sold under trade names including Advil and Motrin).

Research into the effect of painkillers on psychological processes is still at an early stage. Although the results thus far give great cause for concern, the California researchers say it is premature to have drug regulators issue special alerts – although they should start thinking along those lines.

As they conclude: “Found in medicine cabinets across the world and used multiple times a week by people of all ages, these drugs are woven into modern life.” But they may be shaping modern life in a way that nobody could imagine was possible.

Autism and ADHD, too?

Everyday painkillers aren’t only influencing psychological processes (see main article) – they could also be affecting the way the brain develops in the womb.

If so, they could be an unsuspected cause of the rising epidemic of autism and ADHD (attention-deficit, hyperactive disorder), researchers from the University of California, Santa Barbara, fear.1

Several population studies have discovered an association between women taking painkillers when pregnant or breastfeeding and an increase in cases of autism and ADHD.

Prozac crazy

Before the late 1980s, mass shootings were a rarity – then Prozac (fluoxetine) came on the market as the ultimate SSRI pick-me-up for anyone who was depressed, anxious or felt life was just against them.

And this was the pivotal moment when disturbed people were given Prozac or a similar SSRI – and got hold of a semi-automatic weapon, says the mental health watchdog the Citizens Commission on Human Rights (CCHR).

There have been too many mass shootings where the perpetrator was taking antidepressants – or just withdrawing from them – for it to be a coincidence, the CCHR states.

One of the first associations was noted with the Columbine shooting – still seen as emblematic of a new disturbing trend – when Eric Harris and Dylan Klebold killed 12 students and a teacher. It was later discovered that Harris was taking Luvox, an SSRI.

And the trend continued. The Virginia Tech shooter, who killed 32 people, was on an antidepressant, and James Holmes, who opened fire in a Colorado cinema, killing 12 and wounding 58, was under the care of a psychiatrist, although the drugs he was being prescribed haven’t been revealed.

As the CCHR points out, of the 31 drugs listed as causing violent behavior, five of the top 10 are antidepressants: Prozac, Paxil, Luvox, Effexor and Pristiq.




Policy Insights Behav Brain Sci, 2018; 5: 82-9


J R Soc Med, 2016; 109: 381-92


BMJ, 2015; 351: h4945


World Psychiatry, 2015; 14: 245-7


Soc Cogn Affect Neurosci, 2016; 11: 1345-53


Science, 2003; 302: 290-2


Psychol Sci, 2010; 21: 931-7


Psychol Sci, 2013; 24: 966-73

Autism and ADHD



Policy Insights Behav Brain Sci, 2018; 5: 82-9

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