India, May 1 -- A five-year-old girl was brought to my clinic not long ago. She seemed to be behind on her milestones, slower to speak, less engaged than children her age. Her developmental assessment placed her at the level of a three-year-old. Her mother was concerned.

The child had not been ill. There was no diagnosis to point to. But when we spoke about the previous two years of COVID-19, the picture became clearer: prolonged school closures due to lockdowns, resulting in her spending most of her time at home, screens replacing playtime, and meals being simpler and less varied than before. Her brain, in those quiet years, had not received what it needed to grow. She was not an exception.

Across clinics, paediatricians and developmen...