112 Oxytocin, Arginine Vasopressin and Autism Spectrum Disorder
were relatively homogenous, restricted to high functioning males (i.e., a lack of
comorbid intellectual disability), and there were consistent sample sizes (14–33
participants).
In numerous investigations, where repeated administration of oxytocin was
delivered over a 6‐ or 8‐week administration period, and ASDs were compared
with a placebo group, the study individuals in the oxytocin group did not sig-
nificantly improve in measures of social cognition, caregiver ratings of repeti-
tive behaviors, and other clinical ratings of improvement. However, secondary
outcome analyses suggested the oxytocin group showed improvements in the
RMET test, caregiver reported quality of life, and lower order repetitive behav-
iors (stereotypy and self‐injury).
Of particular note, there were two unexpected significant findings of the lat-
ter study. First, parents who believed their child had received oxytocin reported
significant improvements in their child’s behavior over time irrespective of
actual treatment assignment (oxytocin or placebo). This finding emphasizes
the significant potential for expectancy biases to mask treatment efficacy
within clinical trials of children with ASD. When investigators are asking par-
ents or caregivers about the progress or conditions of their ASD children, one
should be skeptical of the reporting and the biases that are embedded in the
responses.
Secondly, this study was the first that recruited a wider range of participants,
not only high functioning ASD individuals, but including individuals with ASD
and intellectual disability; the potential efficacy of oxytocin may have been
masked by the greater amount of diagnostic heterogeneity within this sample.
This brings us to the point of the spectrum again. As we have already men-
tioned, ASD is a spectrum and if oxytocin receptor neurons or other progeni-
tor neurons are damaged early during fetal development (that results in
extreme intellectual disability) then exogenous oxytocin may be of no real
value, since the receptors are not there to carry out the signaling tasks. However,
in high functioning ASD, oxytocin may bring good and positive effects.Summary and Conclusions
Oxytocin is a neuropeptide (nonapeptide) made up of nine amino acids that is
evolutionarily highly conserved. It is mainly synthesized in magnocellular neu-
rons in the supraoptic and paraventricular nuclei of the mammalian hypo-
thalamus. Oxytocin functions by binding to oxytocin receptors in specific
areas of the brain and peripheral tissues. Oxytocin regulates coping with
stresss, moods, and social behaviors. Most significantly, oxytocin is involved in
attachment, pair bonding, sexual reproduction, maternal behavior, stress
response, social memory, emotional cognition, and social interaction.
Abnormalities of oxytocin due to either low levels of oxygen or genetic defects