(Marie Lafrance for The Washington Post)

My mother is birdlike. Diminutive. A waifish whisper of the woman she was. She sits nervously in the psychiatrist’s office. I sit at her side, at her instruction, the most forceful thing she’s done all day: “Sit here,” she says, “beside me.” Occasionally she grips my arm.

And we recount her story, history, again. She has suffered from debilitating clinical depressions since she was 38. Regularly. The psychiatrist asks, “How many episodes do you think you’ve had? Six? Seven?” Mum gasps. I almost laugh, the suggestion seems ridiculously optimistic in light of our experience. “God, no,” says Mum. “Dozens.”

For depression has been the pattern for half of Mum’s life and, as a result, most of mine. I described that first collapse in childishly plump 13-year-old handwriting in my journal: “my mum has Depression,” the capital letter to emphasize its enormity. A proper noun, a proper illness, my dad said. I have sat beside her in shrinks’ offices more times than I can count in the following 37 years. I estimate she has lost more than a decade in the last three to this robber of joy; the current episode is almost two years old. It came less than 12 months after the preceding episode.

Mum says depression is not the opposite of happiness, it is the opposite of vitality; depression steals her life away from her. And it steals her away from us. I love my mum but I hate her sickness; I abhor how it changes her from engaged to disinterested, from enthused to enervated, from easygoing to irritable, from warmly close to — sometimes — coolly detached.

As professor Jonathan Flint, a geneticist at Oxford University whose focus is molecular psychiatry, puts it, depression is an immensely disabling, hugely common illness with arguably a bigger societal impact in most of the world than any other condition except cardiovascular disease and with a substantial mortality risk given the threat of suicide.

Flint and his team, which included Kenneth Kendler, a psychiatrist at Virginia Commonwealth University, recently published the findings of a study of about 11,000 participants that found what seems to be a link between genetics and major depressive disorder, or melancholia, my mother’s diagnosis. Douglas Levinson, a psychiatrist at Stanford, describes the illness this way: “You can be a loving grandparent, but when you are depressed, you can see your grandchildren and feel no pleasure at all, which makes you feel like a terrible person.”

I am especially struck by this summary of the awfulness of depression: My mother was present 22 years ago at the birth of my eldest daughter, joyfully overwhelmed. A firm bond grew between the two. Yet she has not felt the inclination, the interest, the energy to engage with her granddaughter for months. “Gran hasn’t spoken to me for nearly one and a half years,” my daughter says with a wobble in her voice.

The thought that my mum’s disabling, disconnecting condition might be imprinted upon my DNA is terrifying. I have felt blue in the past, certainly— we cannot expect to be happy all the time — but never has gloom taken deep root for no apparent reason as it does in Mum. Flint dilutes my anxiety: The genetic susceptibility to depression is a complex one, he says, and it does not bear the same clear heritability as, say, cystic fibrosis or Huntington’s disease “when there is quite clearly a single predisposing factor.” My mother has depression, but she also has eyes of hot-chocolate brown and — when well — a calm, measured, wise approach to life. I am green-eyed in every respect. I am her daughter. Not her duplicate.

“While finding a place in the genome that contributes to susceptibility to disease is not the same as finding a gene,” Flint explains — the genome is a being’s complete set of genetic instructions — “it does provide a handhold, a starting place, to work out the biology involved when someone becomes depressed. And understanding the biology makes it possible to develop more-effective therapies.” I imagine Mum’s genome as multiple ropes of beads. Some of the colors mimic those in my own strands — we share a passion for literature, find the same things funny, are both slender — but in parts her necklace is stained with a darkness that leaches the brightness from her life. I hope mine never loses its luster.

I ask Flint whether these findings will help lend gravitas to the illness, give it tangibility. Yes, he says, “to be able to say there’s a clear biological link to depression would be very meaningful to sufferers, would help them to understand they’re living with a real illness.”

I think Mum would find that oddly liberating. It would lend reprieve from the perpetual battle to find excuses for the way she feels, to know it’s not “all in her head.” (Hah, the irony!) And for me — for the people who live with, and love, sufferers — there will be immense relief in knowing none of it is my fault. Depression is often a game of blame.

But could being aware of a possible genetic link to the illness (while giving me shivers down my spine) help protect me and other children of sufferers?

I have absorbed, over time, some awareness of the catalysts that seem to cause my mother to crash, and so I conduct my life to avoid some of the same triggers. As a witness, I have learned that stress undoes her, that apparently inconsequential worries can accumulate until they take over entirely and she can find no peace, no space to eat well or sleep well. I understand that swimming helps me to unwind, I know my long walks encourage a spirit lifting surge of endorphins, I am keenly aware of the imperatives of enough sleep and a sound diet, I write my thoughts out because ordering them neatly, coherently, on the page helps to unscramble my head. I do these things with zealous, religious commitment. Daily.

Over the years I have had to educate myself. If as a young teenager you sat next to your mother as she lay in her hospital bed, her pillow-crazed hair a halo around her pale, bruised-eyed face, as the doctor explained the mechanics of electroconvulsive therapy to your father above your head, it would have been important to go home and understand the imperatives, the usefulness, of ECT without its terrifying, “One Flew Over the Cuckoo’s Nest,” completely mad connotations. Mum has always supported my quest to know more, never shying from my probing questions: “What’s it like, Mum?” “Like living behind glass. You can see life, but you can’t hear it or feel it.” She has shared with me the library of books she has accumulated in a bid to better acquaint herself with her enemy.

Can all this inquiring and my heightened awareness, born of the fear that I may succumb as my mother does (and my grandmother did), help to protect me? Can forewarned be forearmed against this horrible, unwieldy, in-myriad-ways-manifesting illness? I put my question to Flint’s co-investigator in the study, Kenneth Kendler. “The short answer,” he tells me, “from my clinical and research experience, is yes. Awareness of one’s vulnerability can help to reduce risk for depression.”

I realize that short answer is what I need. A single positive word — yes — means I have something Mum does not. Something else depression steals away: hope.

Rowan is a freelance journalist.