Oxytocin and Grandparent Attachment

I a previous post I summarized a review of the emerging research field of oxytocin and human attachment.

This research supports a key role for oxytocin in reproduction and parental infant bonding.   The above mentioned review emphasized the important role of gender, genetic and early environment in the effect individual human variation in oxytocin response.

One additionally related important research topic relates to the effect of ageing on oxytocin-related systems.  Huffmeijer and colleagues from Leidenand Eramus University recently published a review on this topic in the journal Gerontology.

The authors of this review note the importance of oxytocin in parent-infant bonding and argue by extension this system is probably important in grandparent-grandchild bonding.

However, the review notes there is a paucity of research focusing on the age-related effects on the human oxytocin system.  There is extensive data linking oxytocin with prosocial maternal and paternal behavior towards infants.  There is no research examining the role of the oxytocin system in grandparents.

The limited study of the animal human oxytocin system and ageing points to a few key findings:

• Animal studies support a decreased level of oxytonergic activity with age--the results in humans on this area have been mixed
• Older animals with reduced oxytocin activity still have a prosocial response to exogenously administered oxytocin
• The brain amygdala-limbic system has rich neural connections with oxytocin-related neurons but  amygdala volumes decline with age (this effect is more pronounced in Alzheimer's disease)
• With ageing, amygdala connectivity increases with frontal regions but decreases with posterior brain regions
• Age-related amygdala changes may contribute to the decline in emotional recognition with age seen in humans

The authors conclude that the effect of oxytocin in older humans cannot simply be assumed to be the same as in younger adults.   Due to the effects of ageing, oxytocin response (and adverse effects) may be quite different in elderly humans.

Oxytocin research needs to include a focus on the elderly including grandparent-grandchild bonding.  Many children are primarily raised by their grandparents.  Understanding the dynamics of the oxytocin system in the elderly has practical implications for many families.

Readers with more interest in this topic are directed to the free full text manuscript that can be accessed by the PMID

Photo of reddish egret from the author's files.

Huffmeijer R, van Ijzendoorn MH, & Bakermans-Kranenburg MJ (2013). Ageing and oxytocin: a call for extending human oxytocin research to ageing populations - a mini-review. Gerontology, 59 (1), 32-9 PMID: 22922544

Oxytocin and Human Attachment

In a previous post, I summarized a recent review on the neuroscience of human attachment. 

This review highlighted research related to the human bonding and social interactions.  Attachment ability shows significant variability in humans with insecure attachment styles contributing to risk for some mental disorders.     

The neuroanatomical framework for social processing is being investigated with brain imaging techniques.

Hormonal factors including the role of oxytocin also play a key role in social processing.  

Kai MacDonald recently published a review of the prosocial role of oxytocin in attachment.  This review highlighted individual factors that influence variability in oxytocin response.

Molecular Model of Oxytocin

Oxytocin is a central nervous system nine amino acid peptide that has both central and peripheral effects.   Oxytocin can be administered through intranasal mist administration.

The biological effects of oxytocin are complex and include stimulation of uterine contraction during labor, stimulation of breast milk letdown during nursing and modulation of sexual arousal and response.

The effects of oxytocin in social interactions include:

• increases in strength of human bonding
• decreases in anxiety in social situations
• increases in the trust in others 
• increases in calmness and contentment in the presence of a mate

MacDonald notes that individuality in response to oxytocin can be separated into three categories.

Gender: Women appear to be more responsive to the effects of oxytocin.  This may be due to the role of estrogen.  The presence of estrogen upregulates oxytocin and oxytocin receptor production.  Oxytocin response in women is dependent on female hormonal phase with more response during periods of higher estrogen levels.  Administration of intranasal oxytocin has a stronger effect on increasing prosocial behavior in women compared to men. 

Genetic Variation in Oxytocin Receptor Gene and CD38: Genetic variability in the oxytocin receptor gene modulate response to oxytocin with some alleles linked to stronger and weaker responses.  Additionally, genetic variation in the ectoenzyme CD38 have similar effects.  CD38 contributes to the biologic process of oxytocin secretion.  Specific combinations of oxytocin receptor and CD38 genes may contribute to clinical deficits in attachment, stress response and anxiety.

Early Childhood Attachment Environment: Early traumatic experiences appear to impair the development of the oxytocin system.  This may be due to more general adverse effects on neuroplasticity.  Parents with a personal history of childhood abuse are less responsive to the prosocial effects of intranasal oxytocin.  Early traumatic experience may unfortunately contribute to lifelong attachment impairment through this epigenetic effect.

Future research in the role of oxytocin and the oxytocin receptor in a variety of mental disorders will be important.  Intranasal oxytocin clinical trials will be coming in anxiety disorders, stress disorders and disorders of social interaction such as autism and schizophrenia.  Understanding the factors associated with variability in oxytocin response will be key in interpreting the results of future research.

Readers with more interest in this topic can access the free full-text manuscript by clicking the PMID link below. 

Photo of blue heron from the author's files.

Molecular model from the Wikipedia Commons File authored by MindZiper.

Macdonald KS (2012). Sex, receptors, and attachment: a review of individual factors influencing response to oxytocin. Frontiers in neuroscience, 6 PMID: 23335876