Tachykinins are having a party and I’m sitting at home. Why to be more social.

(4 minutes of reading)

What can be at the bottom of it? “I don’t feel like myself.” “I’m stressed.” “I can’t focus.” Whenever these kinds of thoughts appear in my mind, I try to find their source. A potential trigger may be stress from school, work, hormones… Or all of those combined. And how about lack of social contact? Loneliness can be a quiet and underestimated underminer of our mental health. If the period without social contact lasts too long, it can have such a profound effect on our brain that it starts to change. The aim of this article is to remind you how important interpersonal relationships are as one of the techniques of stress prevention and support of brain and mental health. 

This is not a good time

I am an introvert. Aloneness helps me charge my batteries and I need some me time practically even after a conversation with a shop assistant. There is a fine line between beneficial aloneness and harmful loneliness, however. You can sometimes easily overlook the line and head towards the potential consequences of voluntary isolation.

“If I work hard now, I will have more time later.” This and similar phrases hide in my subconscious and have often made me decline an invitation to a coffee, a walk in the park, a night of dancing, or adventurous camping. On other occasions, I turned down invitations because I already had a companion - stress. I shut everybody out, did not answer my phone and immersed myself in my loneliness. I know that everybody will perceive this article in a different way. For some people, social contact is totally natural and they might find it hard to imagine prolonged aloneness. The fact is, however, that many of us postpone social interaction, some avoid it intentionally, and for some, it is less accessible (for example for the elderly). The reasons may vary. What if the river of responsibilities overflows, though, and we are carried away by its torrent? Then we hear ourselves saying, ever more often: “Sorry, I can’t, this isn’t a good time.” Or: “I don’t feel like it.” But the lack of regular human contact has a significant effect on both the soul and the brain. And we may not even realise the connection between some of these consequences and loneliness.

• poor concentration
• memory loss
• dementia
• loss of social skills (e.g. ability to cooperate with others)
• depression
• stress
• anxiety (1, 2, 3).

Loneliness - what does science say?

Research that studied social isolation and its effects on the brain found that the main changes occur in three areas in the brain. These are the prefrontal cortex, the hippocampus, and the amygdala (1, 2, 3). The prefrontal cortex plays a part in complex reasoning and memory, the hippocampus is involved in learning and processing emotions, and the amygdala regulates emotions, such as fear or aggression. Research done on Drosophila flies* brought interesting insight into this topic when researchers found a relation between prolonged isolation and increased aggression. 

Certain neurochemicals, tachykinins, were accumulated in the studied flies during their social isolation. And precisely tachykinin was one of the main reasons why the flies became more aggressive (4).

What is tachykinin? Tachykinin is a neuropeptide (a small protein molecule) released by certain neurons in case of their activation. Neuropeptides can bind to the receptors of other neurons and alter their physiological functions. These changes can then be manifested even in the function of the neural circuit. 

Another study was done on mice. The researchers were interested to see if similar connections can be observed in mammals as well.

A research team at Caltech found that a significant change in behaviour occurred in mice that were socially isolated for a long time (2 weeks). They became more timid and manifested oversensitive reactions to threatening stimuli. They also started acting more aggressively toward other mice, specifically to strange, unfamiliar mice.

The tested mice went out of the frying pan and into the fire. When they were finally allowed to establish social contact after a long period of loneliness, the changes in their brain sabotaged their efforts through behavioural changes. In mice, the tachykinin gene Tac2 encodes a neuropeptide called neurokinin B (NkB). Tac2/NkB is produced by neurons found in the amygdala and hypothalamus in the mouse brain. These are the areas of the brain that participate in emotional and social behaviour (5). Although this research was done on mice, the authors of the study emphasise that people have a very similar system in the brain and the results of this research may contribute to the research regarding the treatment of mental disorders in humans (6).

Like mice, we too are biologically predisposed to regular social interaction, especially in periods of increased stress. Our emotional health is fragile and we do not always realise what it was that upset us this time. A regular dose of meaningful human contact may play an important role in preventing anxiety and depression, in ourselves and our loved ones. 

Action steps and prevention:

• Don’t let tachykinin accumulate in your brain and mark down regular get-togethers with your friends in your diary.
• Perhaps you have enough social contact (perhaps too much of it). Not everyone feels comfortable in social situations, however. Is there someone around you who you know has problems or anxiety related to social interaction or finds it difficult to socialise for whatever reasons? A short phone call or visit can mean more for them (and their brain) than we can imagine.

*Drosophila flies are often used in scientific research. One of the reasons is their great genetic similarity to humans (7).

Bibliography:

1. Bzdok, D. and Dunbar, R., 2020. The Neurobiology of Social Distance. Trends in Cognitive Sciences, 24(9), pp.717-733.
2. Evans, I., Martyr, A., Collins, R., Brayne, C. and Clare, L., 2019. Social Isolation and Cognitive Function in Later Life: A Systematic Review and Meta-Analysis. Journal of Alzheimer's Disease, 70(s1), pp.S119-S144.
3. Arzate-Mejía, R., Lottenbach, Z., Schindler, V., Jawaid, A. and Mansuy, I., 2020. Long-Term Impact of Social Isolation and Molecular Underpinnings. Frontiers in Genetics, 11.
4. Asahina, K. et al., 2014. Tachykinin-expressing neurons control male-specific aggressive arousal in drosophila. Cell, 156(1-2), pp.221–235. 
5. Zelikowsky, M. et al., 2018. The neuropeptide TAC2 controls a distributed brain state induced by chronic social isolation stress. Cell, 173(5). 
6. Dajose, 2018. How social isolation transforms the brain. California Institute of Technology. Available at: https://news.caltech.edu/about/news/how-social-isolation-transforms-brain-82290 [Accessed March 22, 2022]. 
7. Yourgenome, 2021. Why use the fly in research? Yourgenome. Available at: https://www.yourgenome.org/facts/why-use-the-fly-in-research [Accessed March 17, 2022].