Effect of Propranolol On Eye Contact in Autism Spectrum Disorder

Background: Individuals with autism spectrum disorder (ASD) exhibit poor eye contact with others from an early age.  Recent physiological evidence suggests that direct eye contact may be physiologically stressful to those affected by ASD.  Stress is well known to activate the noradrenergic system.  Therefore, an agent that could decrease the stress related to eye contact by acting to block noradrenergic activation might increase eye contact in ASD.  Propranolol, a nonselective beta blocker, produces noradrenergic blockade with central and peripheral nervous system effects.  Propranolol is commonly prescribed for situational anxiety (stage fright, test anxiety, etc).  Thus, we wished to determine the effect of propranolol on eye contact in ASD. 

Objectives: To determine the effect of propranolol on eye contact in ASD.

Methods: Fourteen individuals with ASD (mean age 18.9 years, mean FSIQ 104, 10 male) participated in the two separate eye tracking sessions.  One was performed one hour after 40mg propranolol and the other was performed one hour after placebo, with the order of drug administration counterbalanced.  At each session, subjects were asked to look at a series of 10-second video clips of novel faces with neutral expressions.  An ASL eye tracker was used to monitor and record participants’ eye movement scan patterns while viewing the video.  Eyetracker data was analyzed using the EyeNal and FixPlot programs with ASL.  Time spent looking at the eyes, the mouth area, and the remainder of the face was computed and compared between drug conditions.  Heart rate and blood pressure were also compared between conditions.

Results: T-tests revealed a significant decrease in amount of time fixating on the mouth (t(13) = 3.851, p = .001) and an increase in amount of time fixating the eyes (t(13) = 2.473, p = .014) with propranolol as compared to the placebo condition.   There was no effect of drug on time spent looking at the remainder of the face.  Systolic blood pressure and heart rate were also significantly lower on propranolol as compared to placebo.

Conclusions: Preliminary evidence from the present study using video clips of faces suggests that propranolol may improve eye contact in ASD.  Further studies will need to explore its effects on other aspects of impaired social interaction in ASD.  Given the previously demonstrated cognitive effects of propranolol in ASD, further exploration of the clinical effects of this drug is warranted.