Neuroscience of Social Isolation

By Shirin Emma Herzig

As we enter 2021, the novel coronavirus (CoV) disease 2019 (COVID-19) remains a threat to global health and economies. Since the beginning of the pandemic, one of the most striking changes to daily life has been maintaining social distancing and limiting in-person social interactions. Social relationships have long been understood to act as a protective factor against a wide range of health conditions. In the coming years, it may be particularly important that mental health professionals understand how social isolation impacts brain functioning and psychological well-being. 

The concept of social isolation stress (SIS) developed after researchers in the 1960s found that isolating rats for 13 weeks caused hyper emotionality and abnormal reactivity when handling (Hatch et al., 1965). While the effects of SIS vary in nature and severity across species, a lack of social contact in humans is correlated with increased rates of neuronal disorders and cognitive deterioration (Mumtaz et al., 2018). The animal brain is persistently adapting throughout the lifespan as a result of both genetic and environmental factors (Meaney & Szyf, 2005), which includes one’s social environment of lack thereof. 

Due to ethical implications, studies examining the neurological effects of SIS on humans are rare; however, there are many rodent studies that explore these subjects. Since human and rodent brains share similar structures and cell types, rodent studies help illuminate the effects that SIS may have on humans who experience social isolation. As young children are particularly susceptible to environmental changes, a common concern is how social isolation affects the development of young children. Yamamuro et al. (2017) found that rats that were isolated during the critical period, 2 weeks after weaning, exhibited a reduction in excitatory synaptic inputs and deterioration in action potential properties in prominent h-current cells located in the medial prefrontal cortex (mPFC). Neuronal connections are particularly important for young animals, and these findings suggest that a lack of social interaction during the critical period may result in decreased neural circuitry between the mPFC and subcortical targets (Yamamuro et al., 2017). Utilizing a neurobiological model of rodent schizophrenia, induced by rearing rats in isolation, Fabricius et al. (2010) found that male rats reared in isolation had significantly smaller brain volume (specifically the hippocampus, dentate gyrus and CA2/3), and larger lateral ventricles than rats raised in a group environment. The brain changes observed in male rats raised in isolation corresponded to those observed in schizophrenia (Fabricius et al, 2010). While social isolation measures instilled to combat COVID-19 are not directly comparable to the condition of raising a young child in complete isolation, rodent studies such as these suggest that young children who are experiencing less social interaction as a result of the pandemic may experience similar negative effects on brain connectivity and growth. 

While understanding the effects of SIS on young children may be particularly important, many studies have also explored SIS in adult and elderly populations. Multiple previous studies have found a relationship between social isolation and the development of Alzheimer’s disease, age-related cognitive decline (Wilson et al., 2007), and dementia (Heinrich & Gullone, 2006). A study by Stranahan et al. (2006) found that SIS in adult rats delayed the neurogenesis-promoting effects of exercise. In the context of COVID-19, the results of the following study suggest that exercise alone is not effective at reversing the detrimental effects social isolation may have on neurogenesis. 

While there is ample evidence of the physical and mental health challenges associated with SIS, fewer studies have explored the neurological benefits of virtual social interactions in relation to the negative effects of SIS. Even in the face of a global pandemic, many people have maintained social relationships through virtual interactions. In regards to phone calls and instant messaging, a primary disadvantage of non-video virtual communication is the loss of subliminal facial cues that relay important information such as emotional expressions or one’s mental state (Dunbar, 2018). Tabibnia and Lieberman (2007) found that subliminal emotional and motor synchronicity between two people engaging in a social interaction is intrinsically rewarding. These studies support the notion that face-to-face communication is an important aspect of social connectedness, but the question remains; does this translate to video calling platforms such as Skype, Zoom, or Facetime? 

Previous studies have shown that participants rate video calls as a higher quality of social interaction than phone calls or text messages, and that the length of interaction is positively related to rates of happiness only for video calls (Tatiana et al., 2012). Similarly, participants rated face-to-face and Skype communication as equally satisfying, and rated both as significantly more satisfying than phone, messaging, SMS messaging, text, e-mail, or text-based social media such as Facebook (Tatiana et al., 2012). Further, many studies have found commonalities between the number of social contacts and structure of social networks maintained by individuals in real life and online (Dunbar et al., 2015). These studies suggest that humans have adapted particularly well to maintaining social networks via the internet, and that video calls may be as beneficial as in person communication. However, further research must still be conducted to better understand if digital communication can combat the negative health effects of SIS, particularly in regards to neural connectivity and cognition. Understanding these processes are critical for developing novel therapies or applying relevant interventions to mitigate the effects of SIS while remaining conscious of social distancing and COVID-19. 

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