Temper outbursts and disruptive behaviors are among the most challenging aspects of PWS, both for the individual with PWS and their family (Tsai 2018). Emerging research suggests that vagus nerve stimulation (VNS) may hold promise as a treatment for reducing temper outbursts in PWS.
Temper Outbursts in PWS: Past Strategies
Although not all individuals with PWS display temper outbursts, they are very common, persist throughout adulthood, and can be quite severe, sometimes lasting for hours, and can be associated with physical aggression and/or destruction of property (Rice 2015, 2018). Not surprisingly, these behaviors can significantly limit the ability of the person with PWS to have positive interactions at home, school, and work.
To date, the primary strategies to manage temper outbursts in PWS have focused on providing space to calm down and distracting the individual, which can be helpful, but not always. Alternative approaches to reduce the frequency and intensity of temper outbursts in PWS are needed.
Early Clues: Vagus Nerve Stimulation Research in PWS
Dr. Tony Holland, a psychiatrist at the University of Cambridge with extensive experience studying PWS, first noticed the potential impact of vagus nerve stimulation (VNS) during a study focused on obesity. He was testing whether a device called a vagus nerve stimulator (VNS) could help reduce hunger and lead to weight loss in people with PWS.
While the study did not show meaningful weight loss, something unexpected happened. Parents and participants reported a noticeable reduction in temper outbursts while using the VNS device. (You can learn more about this research in Dr. Holland’s publication in the Journal of Intellectual Disability Research or in a short documentary about the study.)
A Follow-Up Study Using a Non-Invasive Device
Encouraged by these observations, Dr. Holland launched a second study—supported by FPWR—to test a non-invasive version of VNS, called transcutaneous vagus nerve stimulation (t-VNS). Instead of requiring surgery, this device stimulates the vagus nerve through the ear.
The results of this study were published in the journal PLOS ONE.
Five adults with PWS (two men and three women, ages 22–41) participated in the study. Each participant served as their own comparison.
The study was conducted in three phases:
- Baseline phase (4 months): Participants wore the device daily, but it was not turned on.
- Treatment phase (12 months): Participants used the activated t-VNS device for four hours per day.
- Reduced-use phase (1 month): Participants used the device for two hours per day.
After nine months of using the active device for four hours each day, four of the five participants experienced a significant reduction in both the number and severity of temper outbursts. For one participant, the outbursts stopped entirely.
When participants later reduced device use from four hours per day to two hours per day, temper outbursts increased again in all participants, suggesting that the amount of stimulation may matter.
Importantly, no serious safety issues were reported during the study.
Caregivers also described meaningful changes in everyday life. One caregiver shared:
“Before you couldn’t challenge him on certain things… but now you can and he’s prepared to sit and listen.”
Another explained:
“In a way he… doesn’t know what he’s doing and he can’t control it, but [since the VNS] something clicks and he just calms.”
Challenges and Limitations of our VNS Research to Date
One challenge with VNS—seen in other conditions such as epilepsy—is that it can take time for benefits to appear. In this study, improvements in behavior developed gradually over weeks to months.
Another limitation is the small number of participants. Even so, the reduction in temper outbursts was significant, and both participants and caregivers reported that the therapy made a meaningful difference in their daily lives.
Next Steps in VNS Research For PWS
Dr. Holland's study of 5 individuals wearing a t-VNS device suggested t-VNS may be a safe and promising new approach for reducing chronic temper outbursts in PWS. The findings also suggest that the vagus nerve may play an important role in emotional regulation, offering new insights into why these outbursts occur.
FPWR is actively advancing this promising research and fully sponsoring the VNS4PWS clinical trial evaluating a non-invasive external vagus nerve stimulation (VNS) device. More than 100 individuals with PWS, ages 10 and older, have enrolled in the study and will wear the device for four hours each day over a nine-month period. This trial represents an important step in exploring new approaches to support emotional regulation and behavior in PWS. We look forward to sharing results with the community in late 2027.
