We don’t often think mental health is contagious in the same way a virus is. But a depressed person in a family can cause that depression to spread through the family, and an anxious person in a lift can be felt by the others. We humans are mimics, argues Don Forsyth, and we need to catch psychological problems early, so that they don’t spread further than they need to. 

In 2011 millions of citizens of Tunisia protested government authority and repression. The movement spread to adjoining countries, sparking the Arab Spring. Fewer than 10% of US households had microwave ovens in 1978; ten years later they were in nine out of 10 kitchens. On a warm day in June one worker after another fell sick, complaining of nausea, headaches, and dizziness. Rumors circulated about “some kind of bug” that had infested a recent shipment of cloth from overseas, but no bug was ever found. Dozens of injuries resulted when the TikTok Skullbreaker challenge (sweeping a person's legs out from under them) went viral. As SARS-Covid-19 spread around the world, so did resistance to recommended safeguards, suspicions about the source of the virus, and distrust in health authorities.