Summary: Botulinum toxin (Botox) injections can reduce negative emotional responses in people with borderline personality disorder.
Source: MHH
Botulinum toxin (BTX), widely known as Botox, is commonly used to smooth wrinkles. Research now shows that when injected into the forehead it can also reduce depressive symptoms and dampen intense negative emotions in people with borderline personality disorder (BPD).
Professor Dr. Tillmann Krüger, senior physician and research group leader at the Clinic for Psychiatry, Social Psychiatry and Psychotherapy at Hannover Medical School (MHH), together with Privatdozent Dr. Marc Axel Wollmer from the Asklepios Campus Hamburg of Semmelweis University, previously demonstrated clinical benefits of BTX for mood. Their latest work pinpoints how and where BTX acts in the brain to influence these emotional responses.
Using functional magnetic resonance imaging (fMRI), the team visualized neuronal changes in patients with borderline personality disorder after injections into the glabellar region—the area between and just above the eyebrows where frown lines form. The imaging showed that BTX modulates activity in the amygdala, a key brain structure involved in fear and negative emotion processing.
Facial feedback and emotional regulation
Negative moods are often mirrored by contractions in the muscles of the glabellar region. When these muscles contract, they create the characteristic frown or worry lines. Injecting Botox into this area weakens those muscle contractions, which interrupts a bidirectional feedback loop between facial expression and emotional experience.
This mechanism is framed by the facial feedback hypothesis: facial expressions influence emotional states. Professor Krüger explains that a relaxed forehead communicates a calmer internal state and that reducing visible signs of negative emotion can in turn lessen the subjective intensity of those feelings.
Beyond the cosmetic benefit, BTX injections offer practical advantages as a psychiatric adjunct: effects last for three months or more, treatments are infrequent, generally well tolerated, and often accepted by patients as part of a broader therapeutic plan.
Reducing the “emotional constant fire” in the amygdala
Borderline personality disorder affects roughly three percent of the population in some regions and is characterized by emotional instability and impulsivity, often accompanied by heightened amygdala reactivity. The researchers found that four weeks after glabellar BTX injections, patients showed both clinical improvement and measurable reductions in amygdala activity on fMRI scans.
Krüger describes the effect as curbing the “emotional constant fire” in the amygdala that underlies intense inner tension in people with BPD. A control group that received acupuncture experienced clinical symptom relief but did not show the same neurobiological changes on MRI, suggesting a specific neural effect linked to BTX’s interruption of facial feedback.
Further analysis, conducted in collaboration with colleagues in the United States, indicates that BTX’s emotional effects are not limited to the glabellar region. Database research found symptom improvements for anxiety-related conditions when BTX was administered to various muscle groups including scalp, limb, and neck muscles—supporting the idea that changing peripheral muscle signaling can influence central emotional processing.
Despite growing evidence, BTX treatment for psychiatric indications is not yet routinely covered by health insurance. The researchers hope that clearer understanding of the mechanism and consistent positive outcomes will encourage broader acceptance of BTX as an adjunctive psychiatric treatment.
Botulinum toxin itself is the most potent known neurotoxin, produced by the bacterium Clostridium botulinum under anaerobic conditions. Ingestion of contaminated food can lead to botulism, a serious poisoning that blocks neuromuscular transmission.
About this borderline personality disorder and emotion research news
Author: Stefan Zorn
Source: MHH
Contact: Stefan Zorn – MHH
Image: Photo credit: Karin Kaiser / MHH
Original Research: Open access. Study title: “Neuronal effects of glabellar botulinum toxin injections using a valenced inhibition task in borderline personality disorder” by Tillmann H. C. Kruger et al., published in Scientific Reports.
Abstract
Neuronal effects of glabellar botulinum toxin injections using a valenced inhibition task in borderline personality disorder
Previous research suggests that injecting botulinum toxin into the glabellar region can produce lasting reductions in depressive symptoms by disrupting a facial feedback loop that reinforces negative emotions. Such injections have been shown to attenuate amygdala responses to emotional stimuli.
Borderline personality disorder is characterized by excessive negative emotionality, impulsivity, and elevated amygdala reactivity. To investigate how glabellar BTX affects emotional processing and inhibitory control, the researchers conducted an fMRI study using an emotional go/no-go task in a sample of 45 women with BPD.
Participants were randomized to receive either glabellar BTX or serial acupuncture of the head. After four weeks, both groups improved clinically. However, BTX specifically improved inhibitory performance and increased motor cortex activity, while also reducing right amygdala activation during processing of negative emotional faces.
These results provide the first evidence that glabellar BTX injections can produce measurable central neurobiological and behavioral changes in BPD. Because the control treatment produced similar symptomatic improvements without the same neural changes, the observed fMRI effects may be specific to BTX rather than a general correlate of clinical improvement.