Social function improved in autism-spectrum patients treated with the hormone oxytocin, according to a small study.
Following oxytocin inhalation, adults with Asperger's syndrome or high-functioning autism were more inclined to play with the most socially responsive partner in a video ball game, reported Angela Sirigu of the CNRS lab in Bron, France, and colleagues.
Also, when participants were shown pictures of human faces, they were more likely to focus attention on the eyes, an important marker of social interaction, the researchers found.
These behaviors are important markers of social function, Sirigu and colleagues explained in their report, published online in the Proceedings of the National Academy of Sciences. The study compared the effects of oxytocin in 13 individuals with autism-spectrum symptoms. Another 13 age- and sex-matched normal controls also played the video ball game without oxytocin.
"Under oxytocin, patients respond more strongly to others and exhibit more appropriate social behavior and affect, suggesting a therapeutic potential of oxytocin through its action on a core dimension," the researchers asserted.
Oxytocin is best known for its actions in prompting childbirth and lactation, but it is also produced throughout life. Previous research has suggested roles for the hormone in emotional regulation and social behaviors. One study found that inhaled oxytocin made adults more trusting of others in a game situation.
Some investigators have also found that oxytocin levels are depressed in autistic individuals. One of the hallmark symptoms of autism is social withdrawal and impaired responsiveness to other people, marked by such behaviors as greatly diminished eye contact.
Participants in the study were 17 to 39 years old, with an average age of 26. Ten had received clinical diagnoses of Asperger's syndrome, and three were considered to have high-functioning autism.
Patients received either a nasal spray containing oxytocin or an ineffective dummy nasal spray and participated in behavioral experiments 50 minutes later. In the video ball game, participants played a game of toss-and-catch with three cartoon characters whose interaction with the player could vary. Initially, each character sent the ball to the player 33 percent of the time, passing it between themselves the rest of the time. After awhile, the percentages changed such that one character would send the player the ball 70 percent of the time, the second sent 30 percent of balls to the player, and the third sent just 10 percent of balls to the player. The player was promised a payment for each ball he or she received.
The player could return the ball to any character he or she chose. The outcome measure was the number of balls the player sent to each character, reported on an arbitrary 14-point index.
The mean score for non-autistic control participants in sending the ball to the most cooperative character was 12, compared with about 5.5 for the neutral character and 6 for the least cooperative.
The autism-spectrum patients treated with placebo sent the ball in nearly identical proportions to each of the three characters, with mean scores of 6.5 to 7.
Following treatment with oxytocin, the proportion of balls sent to the most cooperative character increased significantly, Sirigu and colleagues reported, with a mean score of 9 compared with 5.5 and 6.5 for the neutral and least cooperative characters.
After the game was over, the autism-spectrum patients were asked to rate their level of trust with the three characters and their preferences for them as playing partners. After placebo treatment, mean trust and preference scores for the three characters were nearly identical.
In the oxytocin condition, however, patients expressed substantially more trust and preference toward the most cooperative character relative to the least cooperative.
Sirigu and colleagues also repeated the ball-toss experiment, with oxytocin and the placebo control, with a second set of seven high-functioning autism-spectrum patients, this time without the monetary incentive. They reported that the results were essentially the same as when participants were paid for receiving the ball, with the same significant differences despite the smaller sample.
Participants also looked at photos of faces on a computer and asked to identify either the gender or whether the face was looking into the camera or away to one side. The focus of participants' gaze was recorded.
Mean time spent looking at the faces, as opposed to elsewhere, was about 20 to 30 percent greater following oxytocin treatment both in the gender identification and the facial-direction tasks.
Moreover, when participants were looking at the faces versus elsewhere, their attention was more focused on the subjects' eyes after oxytocin treatment by about 30 percent in the gender identification task and by 45 percent in the facial-direction task.
"We demonstrated that oxytocin can promote social approach and social comprehension in patients with autism," Sirigu and colleagues wrote. They suggested that the specific effect may be that the hormone reduces mistrust and fear associated with social interactions.
"Future research is necessary to investigate whether a long-term intake of oxytocin may improve real-life social functioning of these patients," they added.