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

Neuroscience of Human Attachment

Attachment is the ability to form human relationship bonds.  Individuals vary in their ability to develop social relationships.  The ability to form secure human relationships plays a key role in successful personal and occupational development.

Attachment theory evolved over 50 years ago.  This theory proposes all humans have an innate biological mechanism that supports social engagement.  This engagement is necessary during infancy to encourage nurturance and provision of a safe environment.

Bowlby is credited with describing attachment theory and he proposed three developmental styles of attachment.  These three attachment styles included:

• Secure attachment: an ability to easily seek and obtain support from others.  This style promotes strong bonds with parents, siblings, friends and later in life allows for bonding with a mate.
• Anxious attachment: a insecure attachment style where emotional support has often been inconsistent during childhood.  Individuals with anxious attachment develop hypersensitivity to interpersonal rejection and have anxiety in social environments.  They may develop a needy approach to relationships constantly seeking reassurance of the strength of social supports.
• Avoidant attachment: an insecure attachment style that may have been characterized by early social adverse environments.  Individuals with insecure attachment style built a wall around their life denying a need or interest in human interactions.

Emerging research in social neuroscience is providing a better understanding of brain mechanisms related to human attachment.  Vrticka and Vuilleumier of the University of Geneva in Switzerland recently published an excellent review of the neuroscience of human attachment in the journal Frontiers in Human Neuroscience.

The authors of this review begin by noting research showing attachment has profound effects in the domains of emotion processing, selective attention and memory.  Insecure attachment individuals are hypersensitive to changes in the expression of emotions in others.   Anxious attachments individuals have enhanced attention to threatening cues.  Avoidant attachment individuals inhibit the memory processing of distressful information.

The authors note social approach behavior appears regulated in specific brain regions including the ventral tegmental area, pituitary, striatum and ventral medial orbitofrontal cortex.  Social aversion appears to be regulated through the amygdala, hypothalamus, insula, anterior cingulate and anterior temporal poles.

Social behavior appears to regulated through both affective evaluation (emotional mentalization) and cognitive control systems (cognitive mentalizations).  These systems interact with hormonal and neurotransmitter domains in influencing social interactions.

The neuroscience of human attachment includes emerging research showing the importance of mental state representation of others (theory of mind).  Mothers with high sensitivity to the cries of their own infants during the post partum period show increased gray matter and fMRI BOLD responses in the prefrontal cortex, superior temporal sulcus and fusiform gyrus.  These regions have been identified as key components engaged in being aware of the emotional states of others.

The authors conclude that the neuroscience of human attachment is beginning to outline key common and distinct elements in avoidant and anxious attachment styles.  Attachment styles appear to be influenced by both environmental history as well as neurobiological factors, some of which may have strong genetic contributions.

Future neuroscience of research will need to move experiments into the "real world" and not be limited to task in brain scanners.  Additionally, future research needs to target early intervention studies in children with attachment problems to find the most effective methods to improve social outcomes.

Readers with more interest in this review are directed to the DOI link below where the free full text manuscript can be found.

Photo of great white egret from the author's files.

Vrtička, P., & Vuilleumier, P. (2012). Neuroscience of human social interactions and adult attachment style Frontiers in Human Neuroscience, 6 DOI: 10.3389/fnhum.2012.00212