During moments of danger, the sympathetic nervous system prompts an increase in heart rate and alertness to confront potential threats. After the danger subsides, the parasympathetic nervous system takes over to restore calm and equilibrium. For those with anxiety disorders, an overly sensitive threat detection system often leads to unnecessary activation of the “fight or flight” response. Individuals with autism spectrum disorder also suffer from this problem, but anxiety treatment options are lacking. “We give what you give for anybody else that has anxiety and hope that it also works in autism,” said behavioral neurologist David Beversdorf. “Sometimes it works. Sometimes it doesn't.”

In a recent study, researchers at the University of Missouri led by Beversdorf found that propranolol, a beta-adrenergic blocking agent that lowers blood pressure by blocking adrenaline, may help lower anxiety in kids and young adults with autism spectrum disorder (1). “The notion of using a beta blocker for anxiety makes a lot of sense,” said Lawrence Scahill, an epidemiologist at Emory University who was not involved with the study. “If you boost the person's parasympathetic tone, they won't be so prone to fight or flight.”

Seventy-four study participants with autism spectrum disorder received either propranolol or placebo for 12 weeks. Participants ranged between 7–24 years of age, and Beversdorf’s team conducted blinded assessments at baseline, six weeks, and 12 weeks. The researchers observed that patients treated with propranolol noticed anti-anxiety benefits. 

Anecdotal evidence from participants indicated significant improvements related to anxiety. For instance, one participant reported, “He was too anxious to take the driving test,” said Beversdorf. “At week six, he had not only taken the test, but he passed and was driving.” 

Propranolol was generally well tolerated, with side effects observed in both the treatment and placebo groups. Physiologically, propranolol led to expected decreases in blood pressure and heart rate, aligning with its known biological effects, and these changes were not linked to significant adverse outcomes.

He was too anxious to take the driving test. At week six, he had not only taken the test, but he passed and was driving. 
- David Beversdorf, University of Missouri

However, the lack of a stringent anxiety threshold for participation may have introduced variability in the anxiety measure, said Scahill. “Had they insisted that people have elevated anxiety to enter the study, even if [propranolol] showed no effect, it would have been more useful,” he said. Accepting individuals with a wide age range may also have diluted propranolol’s effects. “I would have started with adolescents with anxiety because we know we can measure it, and we have a feeling about what would be a positive response,” Scahill said.

Beversdorf’s future research plans include a larger trial focused on anxiety that incorporates a variety of biomarkers to determine which individuals are most likely to respond positively to propranolol. “The nice thing about this medication is that it is dirt cheap and available,” Beversdorf said. “It may add just another option in your bag of tricks.” 

References

1. Beversdorf, D. Q. et al. Randomized controlled trial of propranolol on social communication and anxiety in children and young adults with autism spectrum disorder. Psychopharmacology (Berl.)  241, 19–32 (2024).