messenger

The neurochemicals involved in this process are different than those mediating habit formation and include a chemical messenger called noradrenaline and internally produced opioids such as endorphins.

Growing up around his father’s law office, he became a messenger boy in the state Senate, where he met Gov. Earl Warren, the future chief justice.

When that happens, the immune system "is already super pumped up," says Prof Cruickshank, because the body is busy making chemical messengers called cytokines that help to kill viruses.

"Other services run by MediaLab remain available in the UK – such as Kik messenger, which has implemented age assurance to comply with the Online Safety Act."

The timing coincides with the rollout of a new "national messenger" app known as Max and created by a Russian firm closely controlled by the Kremlin.