Variation in the mu-opioid receptor gene (OPRM1) moderates the influence of maternal sensitivity on child attachment

The endogenous opioid system is thought to play an important role in mother-infant attachment. In infant rhesus macaques, variation in the μ-opioid receptor gene (OPRM1) is related to differences in attachment behavior that emerges following repeated separation from the mother; specifically, infants carrying at least one copy of the minor G allele of the OPRM1 C77G polymorphism show heightened and more persistent separation distress, as well as a pattern of increased contact-seeking behavior directed towards the mother during reunions (at the expense of affiliation with other group members). Research in adult humans has also linked the minor G allele of the analogous OPRM1 A118G polymorphism with greater interpersonal sensitivity. Adopting an interactionist approach, we examined whether OPRM1 A118G genotype and maternal (in)sensitivity are associated with child attachment style, predicting that children carrying the G allele may be more likely to develop an ambivalent attachment pattern in response to less sensitive maternal care. The sample consisted of 191 mothers participating with their children (n = 223) in the Maternal Adversity, Vulnerability and Neurodevelopment (MAVAN) project, a community-based, birth cohort study of Canadian mothers and their children assessed longitudinally across the child's development. Maternal sensitivity was coded from at-home mother-child interactions videotaped when the child was 18 months of age. Child attachment was assessed at 36 months using the Strange Situation paradigm. As predicted, G allele carriers, but not AA homozygotes, showed increasing odds of being classified as ambivalently attached with decreasing levels of maternal sensitivity. Paralleling earlier non-human animal research, this work provides support for the theory that endogenous opioids contribute to the expression of attachment behaviors in humans.

Anxious-depressive attack and rejection sensitivity-Toward a new approach to treatment-resistant depression

This paper aimed to find clues to treatment-resistant depression (TRD) solutions. Depression comorbid with anxiety is often treatment-resistant where anxious-depressive attack (ADA) often lurks. ADA is a recently proposed clinical idea for just a psychological version of a panic attack. It mostly begins with an abrupt surge of intense anxiety followed by uninterrupted intrusive thoughts; lasting ruminations about regret or worry produced by violent anxiety, agitation, and loneliness. Acting-out behaviors such as deliberate self-injury and over-dose may also be observed during the attack. As the basic psychopathology of ADA, rejection sensitivity (RS) was revealed by a structural equation model. It is said that the presence of RS in depressive disorders implies a poor prognosis. The following biological markers for RS were reviewed in the literature: first, the involvement of the μ-opioid receptor function in RS and, secondly, hypersensitivity of the dopamine D4 receptor (DRD4) in the medial prefrontal cortex. The latter has been suggested in fear-conditioned animal experiments. Manipulation of the μ-opioid receptor function together with the DRD4 function may culminate in a treatment for RS, which could contribute to the development of a treatment for TRD via the improvement of ADA.

Variation in the μ-opioid receptor gene (OPRM1) and experiences of felt security in response to a romantic partner's quarrelsome behavior

Research suggests that endogenous opioids play a key role in the creation and maintenance of attachment bonds. Opioids acting at the μ-opioid receptor mediate reward and analgesia and are thus thought to underlie feelings of comfort and warmth experienced in the presence of close others. Disruption of μ-opioidergic activity increases separation distress in animals, suggesting that low opioid states may contribute to social pain. Accordingly, a functional μ-opioid receptor (OPRM1) polymorphism (C77G in primates, A118G in humans) affecting opioidergic signaling has been associated with separation distress and attachment behavior in nonhuman primates, and social pain sensitivity in humans. However, no research has examined the effects of this polymorphism on socioemotional experience, and specifically felt security, in daily interactions between romantic partners. Using an event-contingent recording method, members of 92 cohabiting romantic couples reported their felt security and quarrelsome behavior in daily interactions with each other for 20 days. Consistent with prior work, findings suggested that, relative to AA homozygotes, G allele carriers were more sensitive to their partners' self-reported quarrelsome behaviors (e.g., criticism), showing a greater decline in felt security when their partners reported higher quarrelsome behavior than usual. This is the first study to link variation in OPRM1 with felt security toward romantic partners in everyday social interactions. More generally, this research supports the theory that the attachment system incorporated evolutionarily primitive pain-regulating opioidergic pathways. We also discuss implications of this work for understanding of differential vulnerability to health risks posed by social stress.

Association of the OPRM1 A118G polymorphism and Pavlovian-to-instrumental transfer: Clinical relevance for alcohol dependence

BACKGROUND

Pavlovian-to-instrumental transfer (PIT) quantifies the extent to which a stimulus that has been associated with reward or punishment alters operant behaviour. In alcohol dependence (AD), the PIT effect serves as a paradigmatic model of cue-induced relapse. Preclinical studies have suggested a critical role of the opioid system in modulating Pavlovian-instrumental interactions. The A118G polymorphism of the OPRM1 gene affects opioid receptor availability and function. Furthermore, this polymorphism interacts with cue-induced approach behaviour and is a potential biomarker for pharmacological treatment response in AD. In this study, we tested whether the OPRM1 polymorphism is associated with the PIT effect and relapse in AD.

METHODS

Using a PIT task, we examined three independent samples: young healthy subjects (N = 161), detoxified alcohol-dependent patients (N = 186) and age-matched healthy controls (N = 105). We used data from a larger study designed to assess the role of learning mechanisms in the development and maintenance of AD. Subjects were genotyped for the A118G (rs1799971) polymorphism of the OPRM1 gene. Relapse was assessed after three months.

RESULTS

In all three samples, participants with the minor OPRM1 G-Allele (G+ carriers) showed increased expression of the PIT effect in the absence of learning differences. Relapse was not associated with the OPRM1 polymorphism. Instead, G+ carriers displaying increased PIT effects were particularly prone to relapse.

CONCLUSION

These results support a role for the opioid system in incentive salience motivation. Furthermore, they inform a mechanistic model of aberrant salience processing and are in line with the pharmacological potential of opioid receptor targets in the treatment of AD.

A mu-opioid feedback model of human social behavior

Since the discovery of pain relieving and rewarding properties of opiates such as morphine or heroin, the human mu-opioid system has been a target for medical research on pain processing and addiction. Indeed, pain and pleasure act mutually inhibitory on each other and the mu-opioid system has been suggested as an underlying common neurobiological mechanism. Recently, research interest extended the role of the endogenous mu-opioid system beyond the hedonic value of pain and pleasure towards human social-emotional behavior. Here we propose a mu-opioid feedback model of social behavior. This model is based upon recent findings of opioid modulation of human social learning, bonding and empathy in relation to affiliative and protective tendencies. Fundamental to the model is that the mu-opioid system reinforces socially affiliative or protective behavior in response to positive and negative social experiences with long-term consequences for social behavior and health. The functional implications for stress, anxiety, depression and attachment behaviors are discussed.

Interaction between social pain and physical pain

People often experience two types of pain: social pain and physical pain. The former is related to psychological distance from other people or social groups, whereas the latter is associated with actual or potential tissue damage. Social pain caused by interpersonal interactions causes negative feelings in individuals and has negative consequences to the same degree as physical pain. Various studies have shown an interaction between social pain and physical pain, not only in behavioral performance but also in activities within shared neural regions. Accordingly, the present paper reviews: (1) the interaction between social pain and physical pain in individuals’ behavioral performances; and (2) the overlap in neural circuitry as regards the processing of social pain and physical pain. Understanding the relationship between social pain and physical pain might provide new insights into the nature of these two types of pain, and thus may further contribute to the treatment of illnesses associated with both types of painful experience.