In 1986, a psychologist at Southern Methodist University asked a group of students to do something small: write, for fifteen minutes a day on four consecutive days, about the most upsetting thing in their lives. A comparison group wrote about their shoes, their room, what they had done that day. Then everyone went back to their lives.
Six months later, James Pennebaker checked the university health centre's records. The students who had written about the hard thing had visited the doctor about half as often as the students who had written about their shoes.
That study has been repeated, varied and argued over for forty years, and the core finding has held up better than most things in psychology: putting a difficult experience into sentences changes what it does to you. Not talking about it — writing it. Something about having to choose the words, in order, one after another, turns a shapeless weight into a thing with edges. Things with edges can be put down.
The stranger effect
There is a second finding, from a different corner of the field, that is even less intuitive.
In 2014, Nicholas Epley and Juliana Schroeder asked Chicago commuters to do something most of them dreaded: talk to the stranger sitting next to them on the train. Everyone predicted it would be unpleasant. Almost everyone reported, afterwards, that it had been the best part of their commute. The people who sat in silence — as instructed, and as they had preferred — had the worst.
A year earlier, Gillian Sandstrom and Elizabeth Dunn had shown something similar at smaller scale: people who had more small interactions with acquaintances and strangers — the barista, the person in the lift — reported more happiness and a stronger sense of belonging on those days. Weak ties, it turns out, are not weak.
And long before either of those, in 1975, Zick Rubin had documented the thing everyone already knew from long train journeys: people tell strangers things they have never told their families. The reasons are not mysterious. A stranger has no history with you. A stranger cannot use it later. A stranger will not look at you differently at dinner. The cost of honesty, with a stranger, is nearly zero — and honesty is most of what relief is made of.
Why texting a friend doesn't do it
You would think a friend would help more than a stranger, and for some things they do. But for the thing you are actually carrying, a friend is often exactly the wrong reader, for three reasons.
They know you. Which means they know the version of you that you are supposed to be, and you write to that version, and the honest sentence never gets typed.
It is a conversation. A text arrives and you are expected to keep it going. There is no last message. Nothing gets finished, so nothing gets put down.
It is fast. The relief of Pennebaker's writing came from the fifteen minutes — from having to construct the thing. A text is thirty seconds. It gets the fact across and leaves the weight where it was.
The letter is where the two findings meet
Now combine them. A letter to a stranger is expressive writing (you have to build the sentences) addressed to the one reader with whom honesty is cheap (they don't know you), in a form that ends (a letter has a last line). It is, almost accidentally, the format that both branches of the research would design if you asked them to.
People discovered this long before the studies. It is why the penpal survived email, why "Dear Abby" ran for sixty years, why every religion has a version of the anonymous confession, and why so many of us have a letter in a drawer that we wrote to someone and never sent. The writing was the relief. The sending was optional.
What it feels like from the inside
The people who write on Kindredly describe the same thing in different words, so it is worth saying plainly what the format does.
You write one honest thing about your week to no one in particular. It goes to a few strangers whose writing runs close to yours. One of them answers — not with advice, usually, but with their own small thing. And something in you unclenches that you did not know was clenched: somewhere in the world a person you will never meet read the true version and wrote back anyway.
It is not therapy, and we would not call it that. It is older and smaller than therapy. It is the thing the train does, with sentences.
If you want to try the experiment
Pennebaker's instructions were simple and they still work: fifteen minutes, the real thing, don't worry about spelling, don't show anyone. If you would rather someone read it — someone who cannot use it, who will not look at you differently, who will write back — the desk has fifteen letters on it today and one of them is probably about the same thing as yours. Read it first. Then write yours.
Sources, for the curious: Pennebaker & Beall, "Confronting a traumatic event" (1986); Epley & Schroeder, "Mistakenly seeking solitude" (2014); Sandstrom & Dunn, "Social interactions and well-being: the surprising power of weak ties" (2014); Rubin, "Disclosing oneself to a stranger" (1975).