It is easy to laugh at young people asking for sympathy because ‘I’ve got mental health’. I think I heard the journalist-turned-teacher Lucy Kellaway on the wireless recently noticing in a half-baffled way the tendency of pupils to call mental illness mental health. Mental health hasn’t quite achieved that meaning in standard speech, but it could. It is partly a matter of euphemism. Mad and madness are now hardly usable at all with reference to everyday circumstances, being reserved for different times and cultures, for King Nebuchadnezzar, King Lear or King George.

A mental case is ‘increasingly avoided’, noted the Oxford English Dictionary in its 21st-century revision of entries that required no such cautions in its 1989 edition. Mental hospital, it says, is ‘sometimes avoided as being potentially offensive’, as is mental patient. ‘Psychiatric is often used instead,’ it observes.

Of course a century ago, mental on its own acquired the colloquial meaning of mad. The OED’s first citation for that is from a character in a Dorothy L. Sayers novel: ‘I gather she was a little queer towards the end – a bit mental, I think you people [nurses] call it?’

But in recent years the polite convention has been to talk about mental health. Sometimes it seems that broadcasters speak of little else. They avoid any reference to mental sickness or to bad mental health. But it is possible by rummaging through newspapers to construct an inclined plane of connotations in phrases that use mental health: talking so openly about mental health; mental health issues; mental health problems; mental health challenges; a break from cricket for mental health reasons; mental health patients; problems with drugs and mental health; ‘I really struggled with my mental health’; his battles with mental health.

With that last item, battles with mental health, we have reached a meaning equivalent to mental illness, a parallel with battling cancer.

The irony is that, just as the slang term sick can mean ‘good’, so the slang term insane can mean ‘fantastic, amazing’ – what a generation of hepcats, before today’s hipsters were born, called crazy.