If you’ve got children, you need to watch Swiped – and see how sick their phones are making them | Simon Jenkins

The terrible toll that smartphones are taking on young people is now undeniable. We need to start talking about a ban

Every parent of a school-age child should watch Swiped, the Channel 4 documentary on smartphones shown last week. It was devastating. It told of an Essex secondary school's experiment in response to what it saw as a rise in anxiety and stress among its 11-year-olds. A group of them agreed to surrender their phones for three weeks.

The parents' stories were familiar - of children unable to make eye contact with adults, no longer chatting with ease, spending hours alone and staying awake into the small hours. Some spent five, six, even nine hours a day on their phones. They made friends" with total strangers, received hate mail, suffered panic attacks, went from normal to self-harm. Surveys claim a quarter of British 11-year-olds have now watched online pornography. One child died in tragic circumstances closely linked to their social media use.

Simon Jenkins is a Guardian columnist