Botulinum toxin could improve mental health

Glabellar botulinum toxin (BTX) injections might influence the central nervous system and could help with the treatment of borderline personality disorder (BPD), according to a recent study by German scientists.

Magnetic resonance imaging provided the first evidence showing how BTX injections might modify the behavioural and neurobiological aspects of BPD. These new findings are in line with previous studies on how BTX could be used to treat mental health problems such as depression and anxiety.

In a joint study, recently published in the Scientific Reports journal, researchers from the Asklepios Campus Hamburg of Semmelweis University and the Hannover Medical School examined how BTX injected into the forehead muscles might affect the processing of emotional stimuli and impulsive behaviour.

The research involved conducting functional magnetic resonance imaging (fMRI) on 45 women suffering from BPD after some of them received BTX injections and others received acupuncture. The participants had to control their reactions to certain cues while seeing pictures of faces with different emotional expressions presented to them on a computer screen while the researchers scanned their brains, and the results were measured both before the treatment and four weeks after.

“BPD is one of the most common personality disorders with symptoms of emotional instability and impulsive behaviour,” said senior author of the study Dr Axel Wollmer, from Semmelweis University’s Asklepios Campus in Hamburg. "Patients suffering from BPD experience an excess of negative emotions like anger and fear. Based on previous studies, our hypothesis was that relaxing the muscles in the forehead with BTX will interrupt a feedback loop between the face and the brain and thereby reduce these negative emotions.”

The fMRI scans of the injected patients showed decreased activity in the amygdala region of the brain responsible for processing negative emotions.

Dr Wollmer added: “We also found improvement in the symptoms of the control group treated with acupuncture, however not the neural modifications on the MRI scans, which were present only in the BTX group. The images showed a reduction in the activity of the amygdala in response to emotional stimuli, which is often exaggerated in BPD patients.”

The researchers also noticed that BTX reduced the patients’ impulsive behaviour in the task, correlating with the activation of prefrontal areas in the brain that are involved in inhibitory control.

Emotions expressed on the face affect our mental state; negative emotions such as anger, sadness, or fear often generate vertical wrinkles between the eyebrows. When treated with BTX the underlying muscles are paralysed in this glabellar region which, according to the facial feedback hypothesis, also cuts back the intensity of the expressed emotions.

Previous research also highlighted that the feedback between muscles and the brain might not only work in the glabellar region. In a study in 2021, German scientists, in collaboration with the University of California San Diego, found that BTX can also mitigate anxiety disorders. Anxiety disorders were 22 to 72% less common in patients with BTX than in those who had received other therapies for the same conditions.

The scientists, therefore, concluded that either there is overall body feedback where the areas treated with BTX communicate with the brain – or the botulinum toxin somehow travels and reaches the central nervous system.

Based on the same database, similar research was conducted in 2020 about the possible antidepressant effects of BTX injections. This showed that BTX could be used not only to treat depression as several previous studies had already suggested – but it might also have a protective effect on the condition.

Dr Axel Wollmer said: “The World Health Organization estimates that the number of people suffering from depression is approximately 280 million. Established treatments such as psychotherapy or antidepressants don’t work sufficiently for about one-third of the patients so there is a need to develop novel treatment options, and this is where BTX injections could have a role.”