What's the science?
Social interaction and relationships are rewarding; however, attachment anxiety can reduce rewarding effects of social interaction. Oxytocin is a neuropeptide released from the hypothalamus, known to facilitate social bonding and reduce anxiety. It is unknown how oxytocin may affect the experience of social interaction and anxiety differently in men and women. Furthermore, it isn’t known how brain activity may be altered in the presence of oxytocin in men and women. This week in NeuroImage, Ma and colleagues test the sex-differential effects of oxytocin on social sharing and associated brain activity.
How did they do it?
128 pairs of same-sex friends were randomized into two groups and given a placebo (as a control) or a dose of intranasal oxytocin (as a treatment; group allocation was blinded). Before the experiment participants filled in a) a friendship scale to ensure a high quality of friendship and b) questionnaires that controlled for mood and personality differences between the test groups. Attachment style was assessed using the Adult Attachment Scale. After administration of the placebo or oxytocin, the friends participated in a social sharing experiment where they shared emotional experiences with either their good friend or a stranger (same sex). The pairs performed the same task, and one person was in the MRI scanner (task-based functional MRI scan) while the other person was in an experimental room close by.
They were instructed that they would view an image either alone, with their friend or with a stranger. Then participants were shown images of people, landscapes or animals that were either neutral, positive or negative. After each picture they were asked to rate how positive or negative the image made them feel and how strong their feeling was. They were also asked to report on thoughts related to sharing with their friends after the sharing experiment. The fMRI data was acquired to measure effects on brain activity and functional connectivity and differences between men and women.
What did they find?
Oxytocin increased the positive experience of sharing, particularly for positive emotional content, in female but not male participants. Effects were most pronounced when sharing with female friends but not with strangers. For males, there was no effect of oxytocin on sharing between friends, however, it did increase positive emotion in the stranger > alone condition (i.e. viewing an image with a stranger vs. viewing it alone). Oxytocin generally increased thoughts of sharing with friends when undergoing the sharing with a friend condition. On the neural level the effects of oxytocin in females were accompanied by reduced activity in the amygdala and insula as well as decreased interplay between them, whereas the opposite pattern was observed in males. Moreover, oxytocin reduced the strength of the correlation between attachment anxiety and amygdala activity in females during social sharing with a friend, indicating that the effects of oxytocin may vary with attachment style.
What's the impact?
This is the first study to demonstrate effects of oxytocin on social sharing and which effects differ between men and women. We now know that oxytocin increases the positive experience of sharing with a friend in females but not in males and that brain activity during sharing is differentially affected in females vs. males. Furthermore, the effects of oxytocin on brain activity may differ depending on attachment anxiety. Future research should consider sex-differences when studying the behavioral and brain effects of oxytocin on anxiety, stress and social attachment. For the proposed therapeutic administration of oxytocin in disorders such as autism, sex-differences in responses may need particularly to be taken into account.
Ma et al., Sex- and context-dependent effects of oxytocin on social sharing. NeuroImage (2018). Access the original scientific publication here.