Biopsychosocial intersections of social/affective touch and psychiatry: Implications of 'touch hunger' during COVID-19.

BACKGROUND: Humans are neurobiologically wired for touch receptivity. Social touch is a common and mutual way of expressing affection, care, and intimacy. From an evolutionary perspective, affiliative and affectionate touch are considered necessary for social and cognitive development throughout life-stages and across species. The emergence of the COVID-19 pandemic as a public health threat has mandated social distancing as a measure to contain the global outbreak. Travel restrictions, lockdown, and quarantine have led to separation and segregation, giving rise to social touch deprivation that might have adverse biopsychosocial consequences. METHODS: Affective touch has rarely been discussed within the purview of social psychiatry. We attempted to review the neurobiological, social, and behavioural correlates of social and sexual touch, as well as the neurophysiological models involved. RESULTS: The unmyelinated peripheral C-fibre afferents projecting to insular cortex and somatosensory areas form the prime pathway for affective touch. 'Top-down' modulation via the periaqueductal grey area, rostroventral medulla and sub-cortical structures, and 'Bottom-up' approach via the dorsal horn of the spine form the two theoretical models of 'social touch' system. The mu - opioid receptor (MOR) implicated in the Brain Opioid Theory of Social Attachment (BOTSA) and social neuropeptides like oxytocin and vasopressin are the primary neurochemical substrates involved. Sexual intimacy involves other neurotransmitters, with increased oxytocin activity in the limbic structures, Nucleus Accumbens, Anterior Cingulate, and Prefrontal Cortex. The discrimination and amalgamation of touch senses, their affiliative value and emotional valence in humans are based on a complex interplay between psychobiological, environmental, and personal factors. CONCLUSION: The neurobehavioral and emotional effects of 'touch hunger' and strategies to mitigate it during COVID-19 are discussed in the context of psychoneuroimmunity and stress.