A recent neuroimaging study found that oxytocin administration reduced amygdala activity in individuals with antisocial personality disorder (ASPD), approaching the levels seen in healthy individuals. The findings suggest that oxytocin may have the potential to mitigate the heightened amygdala response to anger in individuals with ASPD.
The study was published in Neuropsychopharmacology.
Oxytocin is a hormone and neuropeptide produced in the hypothalamus, a region of the brain. It plays a crucial role in various physiological and behavioral processes, including childbirth, breastfeeding, mother-infant bonding, sexual activity, and emotional bonding between individuals. In recent years, oxytocin has also attracted attention for its potential role in modulating social behaviors and emotions in individuals with various psychiatric disorders.
The new study aimed to investigate the effect of a single dose of intranasal oxytocin on the responsiveness of the amygdala to emotional facial expressions in individuals with ASPD compared to healthy control participants. The study employed a double-blind, randomized, placebo-controlled, within-subject design.
“Initially, we were interested in the neurobiological processes underlying aggression in antisocial personality disorder,” said study author Haang Jeung-Maarse, attending physician and postdoctoral researcher at the University of Bielefeld.
“Aggression is a hallmark of the ASPD and can contribute to endangering others and one’s own detention. We targeted the amygdala as it is a brain structure involved in emotion processing and we wanted to test whether its function could be modulated by oxytocin.”
“Previous studies relied primarily on examining male study participants who were either children with behavioral problems or incarcerated individuals with psychopathy. There are hardly any studies on women with ASPD. We aimed to uncover similarities and differences in brain function between women and men with ASPD, as well as healthy women and men.”
Participants consisted of 20 men and 18 females diagnosed with ASPD and 20 male and 20 female healthy control participants. The age range for all participants was 18 to 30 years old. Participants in the ASPD were recruited from the General Psychiatry Department of Heidelberg University Hospital, local probation services and institutions offering anti-assault training courses. Control participants were selected based on age and ASPD group IQ.
The study involved two scheduled experimental evaluations four weeks apart, during which functional magnetic resonance imaging (fMRI) was conducted to measure brain activity. In the fMRI task, participants were instructed to classify the facial emotion of various human faces as accurately and quickly as possible by pressing a corresponding button. Participants were asked to rate 72 briefly presented faces depicting angry, fearful, or happy expressions. The faces were presented in a random sequence, with equal numbers of male and female faces for each expression.
The researchers found that individuals with ASPD showed faster responses to angry faces and showed different patterns of amygdala activation than healthy controls in the placebo condition. Oxytocin administration appeared to modulate amygdala activation differently in individuals with ASPD and in healthy controls. When individuals with ASPD were given oxytocin, the activity in their amygdala decreased.
Indeed, the amygdala activity in individuals with ASPD who received oxytocin was similar to the activity observed in the amygdala of healthy individuals who received the placebo. This suggests that oxytocin has the potential to reduce the heightened amygdala response to angry faces in individuals with ASPD.
“Oxytocin has become known as the ‘love hormone’ or ‘cuddle chemical’ because it is released during social bonding,” Jeung-Maarse told PsyPost. “It was first recognized for its role in mothers during childbirth and breastfeeding. However, it can also affect individuals differently depending on their mental state and gender. We found that it decreased amygdala activity in response to angry faces in ASPD, whereas it did the opposite in healthy individuals. We also found a more profound effect in women.”
“Crucially, we found an increased amygdala response to angry faces in ASPD. This contrasts with findings in individuals with psychopathy, where lower amygdala activity has been reported in response to fearful faces (“fear blindness”). Since psychopathy is discussed as a subtype of ASPD, our finding is surprising.
The study included the largest sample of individuals with ASPD in fMRI research, the researchers said. “I’m still amazed that we were able to include complete data from 38 people with ASPD,” noted Jeung-Maarse.
However, there were some limitations. The study did not include a clinical control group, meaning there was no set of individuals with a different clinical disorder for comparison. It is important to note that a significant portion of the ASPD sample in the study also met the criteria for psychopathy. However, due to the small number of participants in the correlation analysis (only 9 of 20 male ASPD participants and 7 of 18 female ASPD participants), researchers were cautious in drawing conclusions from these analyses.
ASPD is a recognized mental disorder characterized by a constant disregard for the rights of others. People with ASPD often display behaviors such as deceitfulness, impulsivity, and a lack of empathy or remorse. Psychopathy, on the other hand, is a set of personality traits associated with antisocial behavior. It is not an official diagnosis but is evaluated using specialized tools such as the Psychopathy Checklist-Revised (PCL-R). Not all individuals with ASPD are psychopaths, and not all psychopaths meet the criteria for a diagnosis of ASPD.
“We did not include a clinical control group and could not dissect between psychopathic and non-psychopathic individuals with ASPD,” Jeung-Maarse said. “It would be interesting to explore subgroups of ASPD.”
The study, “Effects of Oxytocin on Amygdala Responsiveness to Angry Faces in Males and Females with Antisocial Personality Disorder,” was written by Haang Jeung-Maarse, Mike M. Schmitgen, Ruth Schmitt, Katja Bertsch, and Sabine C. Herpertz.
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