Of everything ever written, few texts have been as influential or strictly adhered to as a dogmatic, rigid, and narrowly interpreted manual that serves as the hegemonic authority of its domain. It’s not the Bible, nor the Qur’an, nor the United States Constitution, nor your college essay. The DSM, ominously abbreviated from the Diagnostic and Statistical Manual of the American Psychiatric Association, is the single authority not only on what constitutes a verifiable mental illness, but also what medications can be prescribed, who is excused from jail because of insanity, who can be trusted with state secrets, and how much insurance will cover for the treatment of some illnesses but not others.

Aside from a few outliers—whom many in the psychiatric community would quickly call fringe groups—everyone who is certified to prescribe medication must abide by the DSM’s definitions of mental disorders and their subsequent treatments. To be approved by the FDA, pharmaceutical companies must tailor their products to the definitions set forth by the DSM, which can change slightly or radically over time with each new edition, depending on what the latest consensus is about arguably the most subjective public health issue.

The DSM is so intertwined and embedded in the institutions of modern society that it’s easy to overlook how it has actually affected our definition of reality. Before its inception in the mid-20th century, our only conceptions of mental illnesses relied on vague and often interchangeable Freudian terms. More often for those who didn’t have the exclusive privilege of attending an institution of higher learning where one can easily learn a Freudian vocabulary—insofar as reading Freud is remotely easy—the common conception of mental illness was that of danger and even criminality.

Just beyond our campus, across the Connecticut River at Connecticut Valley Hospital, a man named Clifford Beers was tortured in what was at the time considered treatment for what we now call schizophrenia. The only reason we know of the horrors Beers faced, and by extension those of the scores of other mentally ill patients at the time, is because he miraculously recovered in spite of abusive treatment, and, eventually, he wrote down his account of what happened. Beers’ memoir, “A Mind That Found Itself,” has an incredible amount of self-awareness and insight into what was undoubtedly a traumatic experience. He chronicles the agony of so-called treatments such as steaming, a technique intended for criminals that even the biggest proponents of torture today would condemn.

“The hot poultices placed upon my feet and ankles threw me into a profuse perspiration, and my very active association with mad ideas convinced me that I was being ‘sweated’—another police term which I had often seen in the newspapers. I inferred that this third-degree sweating process was being inflicted in order to extort some kind of a confession, though what my captors wished me to confess I could not for my life imagine,” Beers writes.

Without the vocabulary of the diagnostic manual, Beers instead infers that he is a criminal who should confess to a crime he isn’t even aware of. Another example of a stirring account of mental illness without a diagnostic vocabulary is that of F. Scott Fitzgerald’s “Crack Up,” an essay that the legendary author wrote as a washed-up screenwriter in his thirties, struggling with what we now would call chronic depression and alcoholism.

Fitzgerald’s “Crack Up” is perhaps the best example of our pre-DSM mental health vocabulary because the true confessional literary memoir he seeks to write and its precise terminology are forbidden to him. Instead of confessing to being a depressed alcoholic, Fitzgerald presents his crisis in existential terms.

“There is another sort of blow that comes from within—that you don’t feel until it’s too late to do anything about it, until you realize with finality that in some regard you will never be as good a man again. The first sort of breakage seems to happen quick—the second kind happens almost without your knowing it but is realized suddenly indeed,” he writes.

Although the first DSM emerged in the mid-20th century, the shift in vocabulary for most Americans didn’t come until the 1980s with the launch of the gargantuan DSM-III. Chock full of new scientific terminology and medications, suddenly the general public had what they thought was a firmer grasp of how to define mental illnesses.

After the release of the DSM-III, barriers of stigma begin to break, most notably with William Styron writing his confessional memoir “Darkness Visible,” which chronicles his near-fatal depression, albeit with several blind spots concealed by his coupling of the DSM III’s terminology and his stunning prose. The rise of medications like Prozac and Xanax seep into American culture. Movies and TV shows like “A Beautiful Mind” and “The Sopranos” begin to depict mental illness as a complicated character trait for productive alpha-males. The DSM’s creation of a new vocabulary even stretches into colloquial American English, with people today mistakenly saying things like “She’s so bipolar” or “I’m really OCD about my résumé.”

So how did we get here? How did such a drastic swing occur in our conception of mental illness that even our casual vocabulary changed, much less our major institutions? That answer is complicated and requires scholarship where there currently is not enough, especially in the realm of memoirs. However, it’s important to understand how and why a document that started off as a shot-in-the-dark experiment turned out to be an all-encompassing authority on the best and often only ways to remedy the maladies of the mind. It’s crazy to think that one book can have all of the answers to some of the most complicated problems of the human condition.