Abraham Lincoln was, by most accounts, the greatest president the United States ever had. He led the country through the Civil War and played a crucial role in the emancipation of enslaved black Americans. Yet despite his professional and political successes, he is said to have suffered from crippling depression throughout his life.

It is a side of the great American president that is not usually covered in history books, and the new documentary Lover of Men: The Untold Story of Abraham Lincolnwhich opens in select theaters September 6, sheds light on this and another aspect of Lincoln’s life that is often overlooked: his sexuality.

The documentary covers Lincoln’s relationships with several men over the years, particularly Joshua Speed, the co-owner of a general store with whom the future U.S. president shared lodgings – and a bed – for four years.

Directed by Shaun Peterson, the film features interviews with over a dozen scholars and historians, offers letters and never-before-seen photographs, and puts forward the theory that Lincoln was probably gay or at least bisexual.

PEOPLE exclusively offers an excerpt from the documentary that focuses on the crucial date of January 1, 1841, which Lincoln called “the fateful first date.”

It was the day Lincoln read in a local newspaper that Speed ​​was going to sell his store. The documentary claims that was when Lincoln first heard of Speed’s business plans, and that New Year’s Day was also when Lincoln learned that Speed ​​would be moving out of their shared home (and bed) and returning to his birthplace of Kentucky to take over his mother’s farm.

According to one expert in the documentary, “Lincoln is devastated,” while another describes the days, weeks and months following Speed’s departure as “the time of his worst depression.”

“Then Lincoln falls into a suicidal depression,” the commentary continues. “They set up a kind of suicide watch. His friends took away his shaving kit and all other sharp objects, such as knives. And he wrote to his partner in the law firm, ‘I am the most miserable man on earth.'”

Then Lincoln begins to read the letter to his partner off-screen: “I am the most miserable man on earth. If all mankind knew what I feel, there would not be a happy face on earth. Whether I shall ever be better, I cannot say. I fear I shall not be better. Now it is impossible to remain as I am. I must die or improve, it seems to me.”

Speculation about Lincoln’s sexuality has gained momentum in recent years, with much of the attention focused on Speed ​​and the fact that he and Lincoln slept in the same bed during the four years they were roommates in Springfield, Illinois, from 1837 to 1841. At the time, Lincoln was a lawyer and in his late 20s to early 30s.

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But was their close relationship simply a reflection of a different era with different social mores? In the early to mid-19th century, it was not uncommon for men to sleep in the same bed for convenience, and the terms “gay” and “bisexual” did not yet exist.

The documentary deals with this. The synopsis states in part: “Lovers of men broadens its view of the history of human sexual fluidity and focuses on the profound differences between the sexual mores of the 19th century and those we have today.”

Lincoln married Mary Todd Lincoln in 1842 and had four sons with her. Nevertheless, he was plagued by depression throughout his life, even while in the White House during the Civil War from 1861 to 1865. These four years were the most difficult of his life.

Lovers of men argues that his “darkest depression” after losing Speed ​​​​may not have been that long ago.

Lover of Men: The Untold Story of Abraham Lincoln will be in theaters on September 6. A portion of ticket sales will go directly to the Human Rights Campaign when moviegoers use HRC’s unique ticket purchase link.

If you or someone you know is considering suicide, please contact the 988 Suicide and Crisis Lifeline by dialing 988, texting “STRENGTH” to the Crisis Text Line at 741741, or going to 988lifeline.org.