Abstract
Evidence from non-human mammals for the involvement of the endogenous opioid system in prosocial behavior is reasonably extensive and robust; however, studies in humans are lacking. This study tests the neuro-evolutionary hypothesis that exogenous opiates, including morphine, heroine, and methadone, decrease separation anxiety and proximity by hijacking the neuro-peptide endogenous opioid system modulating social bonds. Participants were 486 subjects, 43% male, with ages between 18 and 62 years (M = 26.4; SD = 9.4), divided in three naturalistic groups: 1: addicts in drug-free treatment; 2: addicts in methadone programs; 3: normative non-clinical controls. Instruments: 1) Adult Attachment Scale (AAS) composed of three subscales: Anxiety about being rejected (α = 0.83), Comfort with Intimacy (α = 0.68), and Comfort Depending on Others (α = 0.70). 2) Caregiving Questionnaire composed of four subscales: Proximity Maintenance: (α = 0.83), Sensitivity: (α = 0.76), Controlling Caregiving (α = 0.77) and Compulsive Caregiving (α = 0.68). Results: Multivariate Analysis of Co-variance (MANCOVA) models were computed; gender, age, and education were included in the models. Methadone patients and drug-free treatment addicts were equivalent and reported significantly lower Comfort Depending on Others, Comfort with Intimacy, and Caregiving Proximity. However, methadone users reported significantly lower Anxiety about being rejected than drug-free addicts and were equivalent to non-clinical controls. In addition, correlations between the methadone intake dose and the questionnaires’ scales showed that dose was significantly and negatively correlated with Comfort with Closeness (rs = −0.36; p < 0.01) and with Caregiving Proximity (rs = −0.28; p < 0.05).
Highlights
Humans need intimate relationships of great depths of emotional, psychological and physical intensity for survival, and emotional well-being across the life cycle
All Multivariate Analysis of Co-variance (MANCOVA) assumptions were tested and met by the data except the equality of variances, which were significantly different in the Attachment Scale (AAS) Capacity to be Close scale (F = 3.45; p = 0.004) and the Caregiving Controlling scale (F = 2.90; p = 0.013)
The results of our study show support for the neuroevolutionary theory of social bonds and addiction [ known as Brain Opioid Theory of Social Attachment (BOTSA)] [4], according to which exogenous opiates decrease separation anxiety and proximity maintenance in humans, as in animal models, by hijacking the neuro-peptide endogenous opioid system modulating social bonds [12]
Summary
Humans need intimate relationships of great depths of emotional, psychological and physical intensity for survival, and emotional well-being across the life cycle. Adolescents and adults look for support, emotional and sexual bonding in social interactions and relationships, without which they feel empty and alienated. Social mammals need these affiliative interactions in order to get relief from negative emotions and to get pleasure and joy [1]. It is widely consensual that being able to form positive socio-emotional bonds has implications for physical and mental health as well as for greater social competence. Dysfunctional relationships, social rejection, and withdrawal are associated with a wide range of psychopathologies including drug abuse, anxiety, and depression [2, 3]
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