Dementia Diary: Is my mother’s history of depression key to her developing dementia?

Why does my mother suffer with dementia? Her parents didn’t. They lived well into their 80s. Their bodies might have begun to fail them — compromised mobility hobbled my grandmother, macular degeneration scorched holes in her vision, like a flame to a photograph. My grandfather’s hearing was not as sharp. But their minds? As keenly incisive as they had always been. Their memories intact, they did not lose their words or their stories. They were all there. Until they were not.

So, I puzzle: why mum, why my mum? What sliced the gap, carved the opportunity for this insidious thing to ooze in, like mud, obliterating everything that was once clear? Was it depression? My mother suffered devastating episodes which lasted for months, sometimes years. Is that what did it? The isolation that depression imposes? The shutting down and shutting out? Experts tell us there’s a relationship between depression and dementia.

But Mary McCarron, professor of ageing and intellectual disability at Trinity College Dublin, says the relationship is a complex one, not fully understood, though there is, she adds, “convincing evidence to support the notion that early-life depression is a risk factor for later-life dementia”.

Mum was in her 30s when depression got her.

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Some doctors suggest that depression might create an additional cognitive burden on the brain so if a person begins to develop the pathology of dementia, those who have battled with depression battle harder for “brain space”.

But depression isn’t just about mood, it hijacks physiology too. It throws hormones into flux: happy hormones diluted to useless insipidity, while stress hormones — cortisol — flood the systems of the mentally unwell and might, scientists hypothesise, have an atrophying effect on the brain. And depression disrupts appetite and energy levels; my mother went for months existing on an unhealthy diet of tea and biscuits, scattered crumbs an incriminating Hansel and Gretel trail that revealed her hiding place: curled into a chair, like a comma. A life in hiatus.

Is this what did it? Did the stillness imposed by her depressions set her up for dementia? If she had walked further, faster, more frequently, would she have been safe? Researchers talk of telomere length — telomeres are the “caps” at the end of chromosomes which protect DNA, like the plastic tips at the end of your shoelaces that stop them unravelling. A lifetime of brisk walking could lead to the equivalent of 16 years younger biological age by midlife, I read. How many years did mum lose on account of the near catatonia imposed by a serious psychological disorder?

Or was it the electro convulsive therapy she endured early on, in the 1970s, before anybody talked about mental illness. In jolting her to her senses, did ECT sear the edges of recall. She complained later: “My short-term memory ... afterwards it seemed worse.”

When I asked her neurologist what had caused her stroke — she had none of the usual risks, no hypertension, no cholesterol, no arrhythmia — “depression” he said, quickly and convincingly. And then, by way of explanation: “She sat too still for too long, a clot formed.”

If depression can cause something as catastrophic as a stroke, why not dementia?

Her stroke stole her reading. Agraphia or pure Alexia meant the signalling system between brain and eyes was broken, shattered into a million tiny pieces by cerebral blow. It was hard to find where a sentence began and where it ended, for mum could not decipher the alphabet.

I told myself this was why she lost her proper nouns. All the names of all the people and all the places she has ever known went. Gone. Just like that. I made myself believe the capital Fs for Frankfurt went the way of the names of old friends. And I imagined it was because her command of words on a page, and the grammar that herded them into tidy comprehension, was gone. I did not, not for a single second, imagine there was any other reason. Denial is a blindsiding force.

Depression was what was in my eyeline. Not dementia. Dementia had never been a part of my — our — landscape. Or had it?

It is only months afterwards that I remember a conversation with mum, in the middle of another relentless depressive episode and in the weeks before her stroke. She looked completely blank as I spoke of my best friend. I had grown up with her, mum knew her so well.

Caroline? Who’s Caroline? I told myself: “She is just distracted. Disinterested.” Depression will do that.

Did depression cause her stroke? Was it her stroke that caused her dementia? Vascular incident can prompt the collapse of cerebral architecture: a house of cards comes tumbling down.

You find yourselves going around and round in circles, asking question after question, reading study after study, looking for answers. Needles in haystacks. There must be a reason, you tell yourself. A clue. And you know — with the sting of shame — this is not an entirely altruistic exercise: you become keenly aware of your own cognitive health when you live with somebody whose own is coming undone.

Especially because, like Mum, I am a woman. And women are twice as likely as men to succumb to dementia. Nearly two-thirds of the five million Americans living with Alzheimer’s disease are women. Is this because we live longer — and our dotage is a window of sinister opportunity flung open to create a crack for this to slink through? Is it hormone related? Is it because our neuro-protective oestrogen dries up at menopause so our brains begin to dry up too?

According to Alzheimer’s disease International, by the end of this decade there will 78 million people in the world with dementia; by 2050 there will be 140 million. Somebody in the world, they say, develops dementia every three seconds.

Why mum? Why not?

Keeping Mum: A dementia diary

1. ‘I forgot you were my daughter’
2. Time for a holiday
3. Is depression key?
4. ‘Cures’ are too hard to resist
5. Mum is aghast when I say we’re her daughters
6. Mum remembers nobody
7. Mum only has today
8. Everything about my mother is shrinking

Instagram: @anthea_rowan