HOW COMMON DRUGS AFFECT EMPATHY AND RISK TAKING
HOW COMMON DRUGS AFFECT EMPATHY AND RISK TAKING
NEUROSCIENCE 02 JULY 15 by LIAT CLARK
Two drugs commonly used to treat depression and Parkinson’s have been shown to directly impact moral decision-making when it comes to harming oneself and others.
After taking the serotonin-enhancing antidepressant citalopram, healthy volunteers were willing to pay twice as much to prevent harm to themselves or others versus those taking placebo drugs. Healthy volunteers taking dopamine-boosting Parkinson’s drug levodopa, on the other hand, appeared to shed this altruism — they were shown to be less risk averse, and treated themselves and others equally when it came to inflicting pain.
“We don’t yet know the underlying mechanism,” coauthor on the paper, University of Oxford neuroscientist Molly Crockett told WIRED.co.uk. “It could be that dopamine makes people more sensitive with regard to outcomes, and that in the case of harm aversion — decisions to profit from others’ pain — reward becomes more salient.
“Or it could be that the hyperaltruisim effects in the placebo group are the result of a comparison between others’ pain and our own pain coming with a degree of uncertainty — dopamine could resolve that and make us treat others as ourselves.”
Crockett and her team are analysing brain scans as part of a followup study to try to uncover the neurological mechanisms behind the outcomes. But in the meantime the UCL/Oxford team emphasises that this is definitely not a cause for concern for those taking the medication today — the trial was conducted on healthy volunteers, and thus would have a very different impact than on anyone prescribed and in need of the medication.
“We would certainly expect drugs to have a different effect in aggregate on healthy people than those taking them for medical purposes,” says Crockett. “The baseline is different.” In Parkinson’s for instance, there is a reduction in dopamine production, hence it is prescribed. Once these individuals have taken their medication, says Crockett, “we might expect them to look more like those in the placebo experiment”.
The study does, however, help us edge towards developing a more thoroughly standardised approach to prescribing and tracking the side-effects and benefits of these kinds of medications, and potentially one day a path to using similar drugs to combat antisocial behaviours, including psychopathy.
Crockett explains that if people are prescribed one of these drugs inappropriately, this could throw their brain chemistry out of balance and lead to unintended consequences. She hopes the study will help develop a pathway towards a more stringent set of monitoring procedures that could look out for these kinds of imbalances and act as a warning signal as to what is happening.
“I think this study highlights the fact we need more research,” adds Crockett. “People ask about symptoms, but might not measure the wider array of social behaviours and decision making. It’s important we understand how medicines affect social decisions.”
The experiment itself built on earlier work done by Crockett and her colleagues at UCL and Oxford. That study showed that people tend to spare the pain of strangers rather than themselves when there is an economic benefit involved. It was, says Crockett, explicitly designed in order to set a proven precedent for measuring moral decision-making in the lab. “As you can imagine it’s quite difficult to develop quantitative and well controlled [methods for measuring] moral behaviours in the lab,” says Crockett. An even earlier study showed that people taking single doses of citalopram were less willing to say that it was acceptable to harm one person to save many.
“We thought it was increasing harm aversion, but moral dilemmas are quite complex and we couldn’t tell [for sure].”
They went into this latest experiment, published in Current Biology, with a strong hypothesis based on these earlier results, and the rough paradigm that serotonin is negatively associated with aggression, while dopamine has the opposite affect.
The experiment saw 175 people split into two groups — one for the citalopram study, the other for levodopa. In each group, half were assigned a placebo while the rest received a single dose of the relevant drug.
Participants were all given mild electric shocks that matched their pain threshold, and told that any shocks administered to others would be at this same level. In every trial, a “decider” had to choose between different number of shocks worth different amounts of money — so seven shocks for £10 or 10 shocks for £15. Half of those decisions related to themselves, the other half to strangers — but in every instance, the decider would get the reward, and knew there would be consequences to the decisions (though only they or the stranger would ultimately get the shocks in the end).
Results showed that those taking the placebo would pay around 35p to prevent harm to themselves and 44p to prevent harm to others. The group taking citalopram, on the other hand, would pay (on average) 60p to avoid harm, and 73p to stop strangers feeling pain. Those on levodopa did not exhibit this level of risk-aversion. Instead, they were willing to pay — on average — 35p per shock to prevent harm to themselves or others. Overall it meant they delivered ten more shocks to strangers that those in the placebo group, and also made those decisions faster.
“One conclusion we might draw from our study is that the serotonin system is a good target for drugs for antisocial behaviour,” says Crockett. “Though if you wanted to prescribe that drug specifically to reduce harmful behaviour towards others, that might be effective but would also affect harmful behaviour towards themselves so wouldn’t be an effective route.”
Treating antisocial behaviours in this way, is not that simple. Crockett explains that there has not been a great deal of research carried out into dopamine and serotonin levels in those with psychopathy. Though the speculation that they might have reduced serotonin and increased dopamine fits well with the results.
“The study highlights the value of developing measures like this and other measures that take a computational approach to psychiatry,” says Crockett. “It would have multiple benefits, allowing clinicians to track whether a targeted set of behaviours is improving and hopefully potentially pickup that peripheral behaviours are not being affected unintentionally by the treatment.” In some patients with Parkinson’s, she points, compulsive behaviours such as gambling develop. “It may be that measures like we use in our study could detect the risk of developing those unintended consequences earlier.”