The brain has evolved to respond in predictable ways to threats in the physical environment. Similarly, the brain is attuned to identify and reinforce behaviours that benefit our survival. These threat and reward-related circuits are well described. For example the amygdala, the most well studies threat-related brain region, responds to universally threatening stimuli such as a threat of pain or an approaching tarantula.
But what about more complex, subjective, social stimuli? For example, when a person feels rejected by a friend or partner, what happens in the brain? It is well established that people who have satisfying social relationships and feel cared for and loved by others are more physically healthy and live longer than those who feel socially isolated. In fact, feeling socially connected is protective against a range of conditions such as heart disease and cancer. Despite this, the way perceptions of social connectedness modulate physical health is not known.
A recent research review, published in Nature Neuroscience, suggests that social disconnection may be processed in the brain in the same way as the threat of physical harm. That is, when a person perceives that their relationship with another person is under threat, the brain responds by activating a basic ‘alarm system’. This alarm system sets in motion a range of neurophysiological processes that are the same, whether the threat is physical and in the environment, or perceived and based on individual judgment of a threat to social connectedness. This alarm system includes the amygdala, the anterior cingulate cortex and the insula, all of which are known for their roles in both threat- and pain-related processing.
What happens when this alarm system is activated? The sympathetic nervous system and hypothalamic-pituitary-adrenal axis go into overdrive, increasing inflammation and a compromising the immune system. These processes contribute to many diseases such as diabetes, those of aging, and cancer. New evidence suggests that these responses occur in response to perceived social isolation as well to a physical threat of harm.
On the other hand, how does social connectedness improve health? Research shows that being reminded of your social connections activates basic reward-related circuits that are also activated when learning to respond to beneficial environmental cues. Researchers use the example of seeing a picture of a highly supportive romantic partner; when viewing this picture during painful stimuli, people perceive and report less pain. This simultaneously activates reward-related brain regions including the ventromedial prefrontal cortex and the posterior cingulate. This may be the key to how feeling socially connected can lead to better health. Activation of these brain regions is thought to cause the release stress-reducing neuropeptides such as opiods and oxytocin, which boost the immune system and protect the body from damage due to inflammation.
This is a new and exciting area of research, and suggests what many people have intuitively known for many years: belonging and feeling cared for are critical to good health.