For two years, you did not see friends like you used to. You missed your colleagues from work, even the barista on the way there. You were lonely.
Here is what neuroscientists think was happening in your brain.
The human brain, having evolved to seek safety in numbers, registers loneliness as a threat. The centres that monitor for danger, including the amygdala, go into overdrive, triggering a release of “fight or flight” stress hormones. Your heart rate rises, your blood pressure and blood sugar level increase to provide energy in case you need it. Your body produces extra inflammatory cells to repair tissue damage and prevent infection, and fewer antibodies to fight viruses.
Subconsciously, you start to view other people more as potential threats – sources of rejection or apathy – and less as friends, remedies for your loneliness.
And in a cruel twist, your protective measures to isolate you from the coronavirus may actually make you less resistant to it, or less responsive to the vaccine, because you have fewer antibodies to fight it.