Oxytocin levels tend to be lower in autistic children: A meta-analysis of 31 studies

LAY ABSTRACT

Oxytocin is a hormone that mediates interpersonal relationships through enhancing social recognition, social memory, and reducing stress. It is released centrally into the cerebrospinal fluid, as well as peripherally into the blood, where it can easily be measured. Some studies indicate that the oxytocin system with its social implications might be different in people with autism spectrum disorder. With summarizing evidence of 31 studies, this meta-analysis suggests that children with autism spectrum disorder have lower blood oxytocin levels compared to neurotypical individuals. This might not be the case for adults with autism spectrum disorder, where we could not find a difference. Our findings motivate further exploration of the oxytocin system in children with autism spectrum disorder. This could lead to therapeutic options in treating autism spectrum disorder in childhood.

Blood oxytocin levels are not associated with ADHD tendencies and emotionality in healthy adults

Oxytocin (OT) regulates social and emotional behaviour. Core symptoms of attention-deficit/hyperactivity disorder (ADHD) include social and emotional dysfunctions potentially associated with lower endogenous OT levels. A dimensional approach was employed to examine relationships between plasma OT levels, ADHD tendencies, and emotionality in a healthy adult sample. Moreover, we aimed at replication of results regarding ADHD tendencies and emotionality from our previous work. Subjects were N = 110 healthy Chinese males (M_age: 22.01 ± 2.02 years). Variables of interest were plasma OT levels, individual variations in ADHD tendencies assessed via the Adult ADHD Self-Report Scale Symptom Checklist (ASRS), and positive and negative emotionality assessed via primary emotional traits of the Affective Neuroscience Personality Scales (ANPS). Hypotheses were tested by means of (partial) Spearman and Pearson correlations. Plasma OT levels were neither related to ADHD tendencies, nor to primary emotional traits. ADHD tendencies were significantly related to higher negative emotionality (correlation coefficients: r= .35 to r = .47) and lower positive emotionality (correlation coefficients: r= -.42 to r = -.36). The absence of associations between plasma OT levels and ADHD tendencies, primary emotional traits, and emotionality might be explained by the lack of robust associations between peripheral and central OT levels. Results regarding ADHD tendencies and emotionality replicate previous findings, emphasizing that (sub-clinically) elevated ADHD tendencies associate with dysregulated emotionality. Future studies examining the role of endogenous OT in ADHD should explore the generalizability of the present findings to women and patients with ADHD.