Loneliness NZ

Biology of loneliness

Loneliness is part of our biology.  With social and environmental triggers, it produces psychological (and physical) responses that affect behaviour and our wellbeing. 

To understand the biology of loneliness, we need to consider loneliness in terms of evolution, genetics and neurology.

Evolution of loneliness

Evolution underlies loneliness (Cacioppo et al. 2006; 2014).  As a species, we have evolved to survive.  Some key needs for our survival are so strong that we have evolved emotional motivators to ensure we respond in a timely way to the need.  For example, for the needs of:

  • food.
  • water.
  • preventing and overcoming injury.
  • acting together as a social species.

For each of these survival needs, we have evolved unpleasant aversive signals when our needs are not met. We feel:

  • hungry when we need food.
  • thirsty when we need water.
  • pain when we have an injury.
  • lonely when we lose our meaningful relationships.

These signals provide early warning systems.  When we feel these unpleasant aversive signals, we are motivated to overcome them by respectively:

  • Eating.
  • Drinking.
  • Avoiding injury.
  • Getting connected.

Each of these emotional responses are so fundamental, they apply at a biological level across gender, age, ethnicity, culture, and individual circumstance. That is, the aversive signals – which include loneliness (or social pain) – are biologically programmed into all New Zealanders.

John Cacioppo TEDx talk

For the past twenty years, Prof. John Cacioppo has been the leading researcher on loneliness worldwide.  In this nineteen minute TEDx video he explains the evolution of loneliness.

Humans are a social species

If you didn’t watch the video, then you may be wondering why it is so important that we act together as a social species.  The reason is simple.  We would not have survived otherwise.  Being ostracised or shunned is associated with high rates of mortality in non-human social species (Williams 2003).  As a social species, we are better together.  There are many other animals that are stronger, faster, stealthier, more armoured, and can see and hear better.  But when we combine as a social species, we are unmatched. We are able to create emergent structures that go beyond the organism – such as couples, families, tribes, communities, cultures, and nations. We have evolved genetic, hormonal, and neural mechanisms – such as loneliness – which make it possible to be the dominant social species on earth.

By being a social species, we have been able to:

  • Better protect ourselves from predators.
  • Better protect ourselves from intruders.
  • Source and share food and water more successfully together.
  • Hunt more successfully in packs.
  • Reduce the need for energy expenditure.
  • Build collective infrastructure.
  • Share and build knowledge.
  • Bring up children together.
  • Help those who are sick.
  • Split duties, such as hunting, security, and child-rearing.
In general, as a social species we are able to help each other when in need.  For example, John Cacioppo et al. (2006) write: “In conditions of hardship, hunter-gatherers who had a genetic disposition to experience social pain from social separation (i.e., loneliness) may have been more likely to return to share their food, shelter, or defense with their family and allies to diminish the pain of loneliness.”  They continue: “Individuals with no such feelings of loneliness when separated from others may have roamed the earth better nourished than those who felt distressed by social separation, but the abandoned offspring—and the genetic predisposition of the parents—would have been less likely to survive.”  “As such, loneliness has played an important role in the evolution of the human species, given that reconnecting with others increases one’s chances of survival and opportunities to pass on one’s genes to the next generation” (Goossens et al. 2015).

“Our evolutionary advantage is our brain, and our ability to plan, reason, communicate, and work together.  Our survival depends on our collective ability, not on our individual might.”

John Cacioppo (2013)

Meaningful relationships

Loneliness has evolved to ensure we maintain sufficient meaningful relationships with people we can rely on in time of need.  These are the people who are willing to work together with us for our collective survival.

So what is important is not the quantity of the relationships, but the quality.  The strength and quality of the relationships needs to be such that we can rely on them in time of need – and they can rely on us in their time of need. This is supported by research (Cacioppo et al. 2000; Wheeler et al. 1983) that has shown that it is the quality, not the quantity, of one’s social connections that predicts loneliness (i.e., perceived social isolation) across a lifetime.

So to prevent loneliness we need to maintain sufficient meaningful relationships.  And to overcome loneliness, we need to build more meaningful relationships.  The number of people an individual can rely on in their time of need is an important measure of social connections capital.  It represents an investment by the individual to make them more resilient to unexpected events.

“…it is not the quantity of friends, it is the quality of a few relationships that matter.”

John Cacioppo (2013)

Hypervigilance for social threats

Humans are capable of duplicity and changing allegiances, so simply being with others is not sufficient to ensure one is embedded in a safe, social environment.  Therefore, a simple aversive signal of loneliness motivating us to get connected is insufficient for our evolutionary survival (Cacioppo et al. 2002).  It risks us confiding in, trusting, and depending on people who could literally ‘stab us in the back.’ 

To counter the risk of non-survival from connecting with the wrong individuals, lonely people are hypervigilant for social threats.  In evolutionary history, this hypervigilance helped lonely individuals in environments populated by dangerous foes to connect only with individuals who could assure their survival.

An analogy of the relationship between loneliness and hypervigilance for social threats is provided by the relationship between hunger and taste.  Hunger will not be beneficial if it motivates us to eat poisonous food that kills us anyway.  Since poisonous food tends to have a bitter taste, we have evolved taste buds that are much more sensitive to bitter (e.g. concentrations of 1:2,000,000) than to sweet (e.g. concentrations of 1:200).  This tempers our hunger motivation from eating poisonous foods in the same way that hypervigilance for social threats tempers our loneliness motivation from connecting with individuals that are detrimental to our evolutionary survival.

“In human beings, finding oneself uncertain that one can confide in, depend on, or trust others is not only an unhappy social environment, it can also be a profoundly unsafe social environment.”

“Given it is more costly to fall victim to fatal assault than to forego a friendship, becoming more sensitive to social threats may be beneficial, especially in environments populated by dangerous foes.”

Cacioppo et al. (2014)

Genetics of loneliness

Consistent with the evolution of loneliness, loneliness has been found to have a genetic basis.  What that means is that the susceptibility to loneliness is heritable.  Six behavioural genetic studies of loneliness between 2000 and 2012 found the estimated genetic heritability of self-reported loneliness to be “remarkably similar” and between 37-55% (Goossens et al. 2015), with an average of 45%.  In other words, loneliness is approximately 45% heritable and 55% environmental.

Furthermore, genes have been identified that may be related to loneliness: “Candidate-gene and gene expression studies have pointed to several genes related to neurotransmitters and the immune system. The notion that these genes are related to loneliness is compatible with the basic tenets of the evolutionary theory of loneliness” (Goossens et al. 2015).

“Studies in behavioral genetics indicate that loneliness has a sizable degree of heritability.”

Goossens et al. (2015)

Neurology of loneliness

Our brain appears to be structured with two separate mechanisms for social connection:

  1. The dopamine neurons in the ventral tegmental area of the brain provide the feeling of contentment from social interaction, i.e. being physically in the presence of others.
  2. The dopamine neurons in the dorsal raphe nucleus of the brain appear to create the feeling of loneliness when there is a lack of meaningful social connection.

In particular, if loneliness is an evolved aversive signal, then we would expect there to be neurological circuits in the brain that manage this aversive signal. Preliminary research has identified an area of the brain that responds to social isolation.  The work by Matthews et al. (2016) using mice (a social species) serendipitously discovered a correlative cellular substrate for loneliness. 

While it was known that dopamine neurons within the ventral tegmental area of the brain may mediate positive social reward of social interaction, “a cellular substrate for the negative affective state of loneliness” had remained elusive. The work of Matthews et al. has identified dopamine neurons within the dorsal raphe nucleus of the brain as the potential cellular substrate. 

With two components of the brain driving social connection, we have to be careful not to mix them up when designing loneliness intervention and prevention strategies.  For example, reducing social isolation may temporarily improve social reward with each intervention but may not reduce loneliness.

“Dopamine neurons within the dorsal raphe nucleus are sensitive to acute social isolation, and are able to modulate a ‘‘loneliness-like’’ state upon optical stimulation. These neurons may underlie the subjective experience of social isolation as well as the motivational drive to re-engage in social connections.”

Matthews et al. (2016)

Evolutionary effects of loneliness

An evolutionary understanding of loneliness helps us not only understand the positive effects of loneliness, but also the negative effects.  In evolutionary history, it was important for us to be a meaningful member of a social group – in order to survive.  When we were at risk of being ejected from a social group, we would go into a self-preservation mode. This mode had the evolutionary short-term benefit of helping us get connected at the long-term cost (if we could not get connected) of poorer physical health and mental health.  The evolutionary benefit of immediately getting connected when feeling lonely outweighed the long term negative consequences of prolonged loneliness (if we could not get connected).  If you didn’t get connected, you were not likely to survive anyway – so the negative consequences of prolonged loneliness could not be selected against. So evolution selected for a short-term self-preservation mode to get connected over long-term detrimental effects.

“It is dangerous as a member of the social species to feel isolated, and our brain snaps into a self-preservation mode.”

John Cacioppo (2013)

Other sciences of loneliness

To explore other sciences of loneliness, please click the coloured box of interest.

John Cacioppo (2013), “The lethality of loneliness,” TEDx Des Moines, https://youtu.be/_0hxl03JoA0.

John Cacioppo, J. Ernst, M. Burleson, M. McClintock, W. Malarkey, L. Hawkley, … G. Berntson (2000): “Lonely traits and concomitant physiological processes: The MacArthur social neuroscience studies”, International Journal of Psychophysiology, vol. 35(2–3), p.143–154.

John, Cacioppo, Louise Hawkley, G. Berntson, J. Ernst, A. Gibbs, R. Stickgold, … J. Hobson (2002). “Do lonely days invade the nights? Potential social modulation of sleep efficiency”, Psychological Science, vol. 13(4), p. 384–387.

John Cacioppo, Louise Hawkley, John Ernst, Mary Burleson, Gary Berntson, Bita Nouriani, and David Spiegel (2006), “Loneliness within a nomological net: An evolutionary perspective”, Journal of Research in Personality, vol. 40, p. 1054–1085.

John Cacioppo, Stephanie Cacioppo and Dorret Boomsma (2014) “Evolutionary mechanisms for loneliness”, Cognition & Emotion, vol. 28(1), p. 3-21.

Luc Goossens, Eeske van Roekel, Maaike Verhagen, John Cacioppo, Stephanie Cacioppo, Marlies Maes, and Dorret Boomsma (2015), “The genetics of loneliness: Linking evolutionary theory to genome-wide genetics, epigenetics, and social science,” Perspectives on Psychological Science, vol. 10(2) , p. 213–226.

Gillian Matthews, Edward Nieh, Caitlin Vander Weele, …, Craig Wildes, Mark Ungless, and Kay Tye (2016), “Dorsal raphe dopamine neurons represent the experience of social isolation”, Cell, vol. 164, p. 617–631.

L. Wheeler, H. Reis, and J. Nezlek (1983): “Loneliness, social interaction, and sex roles”, Journal of Personality and Social Psychology, vol.  45(4), p. 943–953.

D. Williams (2003): “The health of men: Structured inequalities and opportunities”, American Journal of Public Health, vol. 93(5), p. 724–731.