We said it all the time at school. "You're demented, mate." It meant stupid, unhinged, out of control, really, it meant whatever we needed it to. Nobody gave it a second thought, because nobody in my life had dementia at the time.

I heard the word again recently on a TV drama. A detective describing the killer. It sat with me for weeks.

Why that word? Why is "demented" the one we reach for when we want to describe a murderer, a lunatic, someone violently out of control — and why does it share its name with the disease that's slowly taking my mum from us?

The same word, sort of

Dementia and demented are not just similar-sounding. They're siblings. Both come from the Latin demens — de- meaning "away from," and mens meaning "mind." To be demented, literally, is to be away from your mind. To have dementia is the same.

This is where it gets awkward. The clinical term we use for a neurological disease and the playground insult for someone acting deranged come from exactly the same place. They grew up together in English and they've been doing different jobs for centuries, but the DNA is identical.

How did we end up here?

Dementia as a medical term has been around since at least the 18th century, when physicians used it to describe severe cognitive decline. Demented as a slang adjective — meaning crazy, insane, violently disordered — evolved alongside it. The medical and the pejorative have been developing in parallel the whole time.

That might not matter if the two uses had eventually drifted apart. They haven't. Open any TV drama, any thriller, any newspaper profile of a crime, and "demented" is shorthand for out of control, dangerous, terrifying. It's still doing the old job. Dementia, meanwhile, is the word we use for a family member losing themselves in slow motion.

These two realities are very hard to hold in the same head at the same time.

The argument for changing it

Advocacy groups and people living with dementia have been pushing back on the language for years. Some argue for person-first terms — "living with cognitive impairment," "person with a dementia diagnosis" rather than "dementia sufferer". Others go further and suggest the word dementia itself should be retired, because of the baggage it carries.

There's weight to this argument. The pejorative meaning of demented doesn't leave the room when we use dementia in a medical context. It carries a charge. When my mum gets frustrated with herself for losing her train of thought, she sometimes calls herself stupid or crazy. She's not. She's ill. But the language doesn't always help her see the difference.

The argument for keeping it

And yet. Awareness of dementia — real public understanding that this is a disease, that it affects one in three people in their lifetime, that it's the most common cause of death in England and Wales — has been hard-won. It's taken decades of campaigning to get where we are, and we're still nowhere near where we need to be.

Changing the word now means starting again. It means new advocacy groups having to explain that whatever replaces dementia is the same thing people used to call dementia. It means the families currently Googling for support finding nothing. It means rebuilding, from scratch, a public understanding that's only just starting to exist.

Most major charities have landed, for now, on keeping the word but fighting the stigma attached to it. Person-first language. Focus on abilities, not just deficits. Push back when the pejorative use appears in public life. Educate rather than replace.

Demented vs. Dementia - My take on the argument

I'm in two minds, which is probably the honest answer. The pejorative connotations of dementia are real, and they do damage. I see that damage in my own mum, calling herself crazy in her own kitchen because the word she knows for what's happening to her is a word that also means dangerous and unhinged.

But I also don't want us to start over. We've made progress. Slow and painful progress but progress none the less. My instinct is that greater awareness will do more than a new word. If we can separate the disease from the insult, allow script writers their description of serial killers, and raise awareness of the conditions that are slowly taking nearly one-million people in this country away from their loved ones, then I think the word is fine. 

My mum is not demented. My mum has dementia. Those two sentences should say completely different things. For now, they don't always. The work is in making sure, one day, they do.