More than 7.3 million Botox injections were performed worldwide in 2021. According to theInternational Society of Aesthetic Plastic Surgery, their number increased by 45.3% compared to 2017. These botulinum toxin injections are generally intended to fill in wrinkles. But what are their long-term consequences? According to a new study, published in Scientific Reports, they could have an impact on brain chemistry and the interpretation of emotions. This scientific research was carried out by researchers from the University of California and AbbVie, a company that manufactures Botox.
Botox and the brain: MRIs to understand the effects of injections
Their work focuses on a small group of participants: ten women aged 33 to 40. “We limited the sample to women only because emotional receptivity varies for men and women and we wanted to reduce variability given our small sample size.”, they say in their study. Between 4 and 14 days before the injection, they carried out MRIs (magnetic resonance imaging), then these examinations were renewed between two and three weeks after the administration of Botox.
Botox injections: changes in brain activity
During these examinations, the scientists gave an exercise to the participants: images of faces were shown to them. “During each test, participants used a box with buttons to indicate whether they thought the faces were happy or angry to ensure that the participants rated the emotional expression of the face.” They did not observe any concrete differences between the two sessions, before and after the injections. On the other hand, the MRI examinations revealed differences at the cerebral level.
The researchers found that after receiving Botox, the women’s brain activity was altered in their amygdala. However, this part of the brain is involved in emotions, it reacts strongly to fear or excitement, for example. “We found an increase in amygdala activity for happy and angry faces after injections (…)note the authors. This sharp change in facial expression can reduce the internal experience of negative emotions and promote positive emotions.“Changes were also observed in the fusiform gyrus, which is important for analyzing faces and facial expressions, when the participants looked at happy faces. According to them, the injections blocked certain muscles which “prevented frowning and reduced the creation of smiling or happy expressions, leading to alterations in amygdala activity for happy and angry faces.”
Botox: future studies to find out the effects on the interpretation of emotions
For the researchers, these results confirm the hypothesis of facial feedback: individuals instinctively reflect the facial expressions of others in order to identify and feel their emotions. “These data contribute to a growing number of publications suggesting that inhibiting facial muscle stimulation can alter neural activity for emotional processing.” They suggest carrying out more extensive studies, with more participants, more different emotions, but also with people who are not in good health. “Emotion modulation studies in clinically depressed individuals already experiencing impairments in emotional processing may reveal stronger effects of Botox injections on emotion-related neural activity.”they point out.