Beta blockers are medications commonly used for treating cardiac problems such as high blood pressure, chest pain, irregular heartbeat and heart failure. In the US, for example, one in five adults aged 60–79 is prescribed a beta blocker.
In a new study, we’ve found the use of beta blockers is associated with lower rates of violence. To explore why this might be, let’s start with some background.
Beta blockers work by blocking the stress hormones and neurotransmitters adrenaline and noradrenaline. These play an important role in our “fight or flight” response. In a stressful situation, adrenaline and noradrenaline mobilise the brain and body for action by increasing the amount of blood the heart pumps out.
Beta blockers prevent the effect of these hormones. This slows the heart rate down, lowers blood pressure, and also decreases tension. For this reason, beta blockers are sometimes used as treatment for common mental health and behavioural problems, like anxiety, depression and aggression.
In recent years, there has been a rise in beta blocker prescriptions for anxiety. They’re also occasionally used in psychiatric clinics and hospitals to manage aggression and violence in patients.
At the same time, there have been concerns that people who use beta blockers could have a higher risk of depression and suicide. But studies have contradicted each other. Some have found that beta blockers reduce mental health and behavioural problems, others have found that they increase them, and some have found no relationship.
The conflicting evidence leaves doctors with difficult treatment decisions. Are beta blockers effective for treating mental health and behavioural problems? Or could they instead increase the risk of serious mental health problems?
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What we did
To answer this, we studied 1.4 million people in Sweden who had been treated with beta blockers. We followed them over eight years, from 2006 to 2013. We wanted to know whether beta blocker use was associated with mental health problems, violence, suicide attempts and suicide deaths.
We identified beta blocker users by analysing data from Swedish pharmacies and followed people through different healthcare, crime and death registers. This was an observational study, meaning we observed patterns of mental health and behavioural problems by examining these outcomes in the registers.
Typically, in an observational study like this, beta blocker users would be compared to non-users. But the two groups may differ on important features, like psychiatric history. This makes the interpretation of results difficult. Are any differences seen due to the beta blockers? Or do the two groups just have different background risks?
So instead, we used a study design where we compared each person to themselves by contrasting periods when they were taking beta blockers with periods when they were not. This way we could account for the influence of factors that are unique for each person, like family and childhood background or psychiatric history.
We found that when people were taking beta blockers, they had a 13% lower risk of being charged with a violent crime by the police. They also had an 8% lower risk of being hospitalised for mental health problems. There was however an 8% higher risk of being treated for suicide attempts or dying from suicide.
We then carried out secondary analyses where we examined subgroups of beta blocker users, for example those with a history of violence or psychiatric problems. The lower risk of being charged with a violent crime when using beta blockers was consistent across the board.
When we broke down hospitalisations for mental health problems into those for depressive or anxiety disorders, we found a lower risk for hospitalisations for major depressive disorders, but not for anxiety disorders.
We also found the higher risk of suicide attempts and suicide deaths was specific to people with serious heart conditions or a history of psychiatric problems.
We know from previous research that there’s a greater risk of suicide following serious heart problems. People may have pessimistic thoughts, be unsure about the future or concerned about their health. So psychological distress associated with heart problems, rather than the beta blocker treatment, could be the main explanation behind the increased suicide attempts and suicide deaths seen in our study.
Could we use beta blockers to manage violence?
Our results on violence align with evidence from small trials on beta blocker treatment. However, we increased the study sample, examined the total general population, and also broadened the outcome to crime.
A possible explanation for our results is that beta blockers help control the body’s fight or flight response to stressful situations, so there is a decrease in the agitation and tension that could lead to violent behaviour.
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Since this is an observational study, it cannot show that beta blockers cause reductions in violence, only that there is a link between them. To understand the role of beta blockers in aggression and violence, studies that use other designs (such as randomised controlled trials and experimental laboratory studies) are needed.
If these studies confirm our results, beta blockers could be used more widely to manage violence in certain people, particularly those with background risk factors such as serious psychiatric problems. Since evidence-based treatments for violence are limited, this is potentially an important finding.