The aetiology of social deficits within mental health disorders: The role of the immune system and endogenous opioids

Abstract

The American National Institute for Mental Health (NIMH) has put out a set of research goals that include a long-term plan to identify more reliable endogenous explanations for a wide variety of mental health disorders (Insel, 2013). In response to this, we have identified a major symptom that underlies multiple mental health disorders – social bonding dysfunction. We suggest that endogenous opioid abnormalities can lead to altered social bonding, which is a symptom of various mental health disorders, including depression, schizophrenia and ASD. This article first outlines how endogenous opioids play a role in social bonding. Then we show their association with the body’s inflammation immune function, and review recent literature linking inflammation to mental health ‘immunophenotypes’. We finish by explaining how these immunophenotypes may be caused by alterations in the endogenous opioid system. This is the first overview of the role of inflammation across multiple disorders where we provide a biochemical explanation for why immunophenotypes might exist across diagnoses. We propose a novel mechanism of how the immune system may be causing ‘sickness-type’ behaviours (fatigue, appetite change, social withdrawal and inhibited motivation) in those who have these immunophenotypes. We hope that this novel aetiology can be used as a basis for future research in mental health.

The Endogenous Opioid System in Schizophrenia and Treatment Resistant Schizophrenia: Increased Plasma Endomorphin 2, and κ and μ Opioid Receptors Are Associated with Interleukin-6

“…Endogenous opioids (EOs) are expressed in the peripheral and central nervous system where they modulate pain, reward, aversion, reinforcement, social bonding, and neurotransmitter signalling including that of glutamate and dopamine [ 16 , 17 ]. During IRS activation, immunocytes produce and release EOs [ 18 ] and express µ (MOR) and κ (KOR) opioid receptors [ 19 ].…”

The Endogenous Opioid System in Schizophrenia and Treatment Resistant Schizophrenia: Increased Plasma Endomorphin 2, and κ and μ Opioid Receptors are Associated with Interleukin-6

“…Endogenous opioids (EOs) are expressed in the peripheral and central nervous system where they modulate pain, reward, aversion, reinforcement, social bonding, and neurotransmitter signaling including that of glutamate and dopamine (Charles et al, 2020;Corder et al, 2018). During IRS activation, immunocytes produce and release EOs (Plein and Rittner 2018) and express µ (MOR) and κ (KOR) opioid receptors (Li et al, 2009).…”