First Long-term Data for 'Love Hormone' in Adult Autism

The hormone and neurotransmitter oxytocin (OT) appears to improve repetitive behaviors and attachment problems in adults with autism spectrum disorder (ASD) over the long term, new research suggests.

"We examined the long-term effects of administering OT through a nasal spray, and the people in the experimental group reported far less repetitive behavior and also reported fewer problems with forming close relationships," lead investigator Kaat Alaerts, PhD, associate professor of neurorehabilitation, University of Leuven, Belgium, told Medscape Medical News.

In addition, she noted, oxytocin's effects persisted up to a year in participants who received oxytocin for 4 weeks.

The study was published online January 21 in Molecular Autism.

First Long-term Look

Also known as the "love hormone," OT is a hormone and neurotransmitter that is synthesized in the hypothalamus. It is involved in complex social behaviors, and in typically developing individuals, it has been "linked to interpersonal bonding, parental care, and the ability to establish trust and form social attachments," the authors note.

For a decade, intranasal administration of OT has been explored as a potential treatment for the main characteristics of ASD. It has been shown to improve core ASD symptom domains, including social cognition/function and repetitive behaviors.

However, previous research has not investigated the potential long-term effects of OT beyond the period of actual administration in adults with ASD.

The goal of the study was to assess "the possibility of long-term retention effects of 4 weeks of intranasal OT administration on core autism symptom domains (including social responsiveness and restricted and repetitive behaviors), attachment characteristics, and general aspects of quality of life in adult men with ASD," the authors state.

To investigate, the researchers randomly assigned 40 high-functioning adult men with ASD to receive either OT (n = 22; mean [SD] age, 25 [± 4.86] years) or placebo (PL) (n = 18; mean [SD] age, 24 [± 5.55 years]).

For 4 weeks, participants in the OT group were treated with a daily dose of 24 IU of OT. Those in the PL group received a saline solution.

The primary outcome measure was improvement in social responsiveness, as measured by the Social Responsiveness Scale for Adults (SRS-A), using both self-report and informant-report versions.

Improvement in repetitive behaviors (assessed with the Repetitive Behavior Scale–Revised [RBS-R]) was a secondary outcome, together with improvement in attachment (assessed with the State Adult Attachment Measure and the Inventory of Parent and Peer Attachment), as well as improvement in quality of life (assessed using the World Health Organization Quality of Life questionnaire).

Measurements were collected at baseline (T0), within 24 hours of the last administration of nasal spray at the end of 4 consecutive treatment weeks (T1), 4 weeks later (T2), and 1 year post treatment (T3).

Not Ready for Prime Time

There were no treatment-specific differences in the primary outcome (social responsiveness) between the two groups, either in the self-related or the informant-related scale.

However, within-group analyses revealed that self-rated SRS-A scores were significantly reduced from baseline in the OT group at session T1 (P = .033), T2 (P = .048), and at trend-level at session T3 (P = .07).

On the other hand, a similar reduction was found in the PL group at session T2 (P = .015), "indicating no specific benefit of OT over PL treatment," the authors write.

Similar results were obtained in the informant-reported SRS-A, except that scores were significantly reduced in the OT group but not in the PL group at session T2 (P = .002 and P = .67, respectively).

By contrast, the OT group showed improvements in secondary outcomes, compared to the PL group, including larger pre-to-post improvements in repetitive behaviors. Between-group analyses yielded a significant main effect of treatment (F[1, 74] = 3.20; P = .04; ŋ² = .08).

Moreover, within-group analyses found that RBS-R scores were significantly reduced from baseline in the OT group at sessions T1 (P = .002), T2 (P = .002), and T3 (P = .02).

Participants in the OT group also demonstrated superior improvement in attachment avoidance, compared to the PL group, with a significant main effect of treatment (F[1,76] = 3.70; P = .03; ŋ² = .09). Moreover, attachment avoidance was significantly reduced from baseline in the OT group at assessments T1, T2, and T3 (P = .016, .018, and .05, respectively).

Participants in the PL group did not experience improvement in either outcome.

There were no differences in the groups in measures of attachment security, attainment anxiety, parent and peer attachment, or quality of life.

By contrast, those in the OT group reported greater improvement in "vigor" (feeling "energetic," "active," or "lively"), compared to the PL group.

Alaerts cautioned that it is too early to apply these findings in clinical practice.

"Although oxytocin is being used in medicine today, this doesn't mean it can quite soon be used to address attachment issues or reduce repetitive behavior in people with autism," she said.

"The findings we're presenting today are the result of a first pilot study. A lot of further research into the long-term effects and mechanisms needs to be done before oxytocin can be used to treat people with autism," Alaerts added.

Exciting Findings

Commenting on the study for Medscape Medical News, Katherine Stavropoulos, PhD, assistant professor, Graduate School of Education, University of California, Riverside, called it "really cool and fascinating" and said that she is "excited that people are looking at [the role of oxytocin in ASD] in such a long-term way."

Stavropoulos noted that this is one of the only studies she has seen that has investigated long-term administration of oxytocin and that its daily administration over a 4-week period is a "unique study design that is important to show whether this is safe — we know oxytocin isn't dangerous, but we don't know what happens every day when used long-term."

It "surprised" her that oxytocin did not produce a difference in social responsiveness, "where one might expect to see changes," but noted that it is "interesting to see" that it produced changes in feelings of attachment and reductions in repetitive behaviors even a year later.

"We often think of oxytocin as something that affects social systems in both the behavior and the brain, but we can also think about its effect on repetitive motor behaviors, which may be malleable and changeable, which is another side of oxytocin administration," she said.

Alaerts said the "next step in studies [of oxytocin and autism] is to administer oxytocin plus behavior therapy, not just the one or the other, but combining them," because the oxytocin "may open people [with ASD] up and make the behavioral intervention receivable."

She added that the present study focused on adults and that their group is conducting a large-scale study of the effects and mechanisms of oxytocin treatment for children with ASD.

The research was conducted in collaboration with Prof Jean Steyaert, head of the Leuven Autism Research Consortium, and was funded by the Branco Weiss Fellowship (ETH Zürich), the Marguerite-Marie Delacroix Foundation, and Research Foundation-Flanders (FWO). The authors and Stavropoulos, report no relevant financial relationships.

Mol Autism. Published online January 21, 2020. Full text

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