"It seems to me to be a very rigorous study with a very large study population, and well balanced by gender, so the prospects for future research and clinical use that it proposes should be very much taken into account. Specifically, in their study of the whole population, they found no consistent links between β-blockers and psychiatric outcomes, while they did, and this seems to me very relevant, with reductions in violence. It prompts us to think about possible therapeutic avenues, proposing, therefore, that the use of β-blockers to control aggression and violence be explored further.   

This work reframes and clarifies previous debates due to inconclusive results. Due to the large case population and the robustness of the study protocol employed, it provides evidence that the widespread use of β-blockers to control anxiety is not supported by the data obtained and that studies using other designs (e.g. randomised controlled trials) are needed to better understand the role of β-blockers in the treatment of aggression and violence.   

Certainly, in all pathologies, multifactorial components must be considered and the individual characteristics of each patient must always be taken into account. 

Beta-blockers are drugs used to treat conditions such as hypertension, arrhythmias, angina pectoris or even anxiety. They work by limiting the effect of adrenergic neurotransmitters (adrenaline, noradrenaline) by binding to and blocking their neuronal receptors. 

Given the well-founded suspicion that β-blocker treatment could lead to adverse psychiatric side effects, a large group of professionals from clinical and research centres in Sweden, the UK and the US have conducted an exhaustive eight-year follow-up of nearly 1.5 million subjects, men and women, most of them over 50 years old, treated with β-blockers, looking at how many of them developed disorders that required psychiatric hospitalisation, suicidal behaviour or violent criminal behaviour. The study was rigorous in its methodological controls. 

The results, of great clinical interest, showed little relationship between β-blocker treatment and psychiatric symptoms, but revealed a significant relationship with a reduction in violence, which opens the door to the possible use of these drugs for the therapeutic treatment of aggressive and violent behaviour. 

This study has several strengths, including the combination of data from different national registers in Sweden, and the within-individual design (i.e. studying whether the risk of violent crime in individuals was different when they took beta-blockers than when they did not). 

I would like to stress that this is an observational study, so we do not know whether the decreased risk of violent crime is due to beta-blockers or to other factors that the authors could not take into account. For more evidence on whether beta-blockers actually decrease the risk of violent crime, more randomised trials should be done. 

Although previous studies are rather sparse, they also point to a possible benefit of beta-blockers in reducing aggression, at least in the short term. 

To better understand whether beta-blockers could be beneficial in reducing aggression, we should first have more randomised trials studying both short- and long-term efficacy and side effects.