Dr. Sigmund Freud died in London from a lethal dose of morphine on September 23, 1939, at the age of 83. His radical ideas on the workings of the human mind transformed psychology and remain controversial to this day. Check out 10 surprising facts about the neurologist known as the father of modern psychoanalysis.

1. Freud’s death may have been a physician-assisted suicide.
By the summer of 1939, Freud was frail and suffering intense pain from terminal, inoperable mouth cancer. On September 21, 1939, Freud grasped the hand of his friend and doctor, Max Schur, and reminded him of his earlier pledge not to “torment me unnecessarily.” He added, “Now it is nothing but torture and makes no sense.” After receiving the permission of Freud’s daughter, Anna, Schur injected the first of three heavy morphine doses. Freud slipped into a coma and never awoke.

2. His chain-smoking led to more than 30 cancer surgeries.
Freud became addicted to tobacco after lighting up his first cigarettes in his twenties. His daily constitutionals always included stopovers at a local tobacco store, and after graduating to cigars, he often smoked more than 20 of them a day. In spite of the warnings from doctors about his chain-smoking, Freud believed the habit enhanced his productivity and creativity. After the discovery of a cancerous tumor inside Freud’s mouth in 1923, doctors removed a large part of his jaw. Although he underwent 33 additional surgeries over the next 16 years and had a large prosthesis inserted to separate his sinus and jaw, Freud never quit smoking.

3. Freud once thought cocaine was a miracle drug.
In the 1880s, Freud grew interested in a little-known, legal drug being used by a German military doctor to rejuvenate exhausted troops—cocaine. Freud experimented with the drug and found his digestion and spirits improved after drinking water laced with dissolved cocaine. He distributed doses to his friends and future wife and touted the drug’s therapeutic benefits in an 1884 paper “On Coca,” which he called ”a song of praise to this magical substance.” However, when Freud gave cocaine to close friend Ernst von Fleischl-Marxow to wean him from his morphine addiction and relieve chronic pain, his friend instead developed a cocaine addiction. With news of other addictions and overdose deaths spreading, Freud stopped advocating cocaine’s medical benefits but continued to use the drug intermittently for migraines, nasal inflammation and depression until the mid-1890s.

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Credit: World History Archive/UIG via Getty images

4. He turned down $100,000 from a Hollywood mogul.
By 1925, Freud’s fame had spread so widely that movie producer Samuel Goldwyn offered the Viennese psychoanalyst, whom he called the “greatest love specialist in the world,” $100,000 to write or consult on a film script about “the great love stories of history.” In spite of the eye-popping offer, Freud turned it down as he did a $25,000 offer the year before from the publisher of the Chicago Tribune to psychoanalyze the famed criminals Leopold and Loeb as they awaited their sensational murder trial.

5. “The Interpretation of Dreams” was initially a commercial failure.
The book Freud considered his “most significant work” produced little fanfare when it was published in 1899. Only 351 copies of “The Interpretation of Dreams” were sold in its first six years, and a second edition was not published until 1909.

6. His famous couch was a gift from a grateful patient.
Freud employed hypnotism when he opened his medical practice in Vienna in 1886, and he found it easier to put patients into trances if they were lying down. When he began to employ his “talking cure” in his psychoanalysis, Freud also had his patients recline on a couch covered with a Persian throw rug given to him as a thank-you gift from a patient named Madame Benvenisti while he took notes in a chair out of sight.

7. The Nazis burned his books and drove him from Austria.
Although an atheist himself, Freud was born into a Jewish family and became a particular target of the Nazis when they rose to power. His books were among those burned by the Nazis in 1933, which caused him to quip: “What progress we are making. In the Middle Ages they would have burnt me; nowadays they are content with burning my books.” After Germany annexed Austria, the Nazis raided his apartment, and the Gestapo detained and interrogated his daughter, Anna. With the assistance of his friend and patient, Princess Marie Bonaparte, a reluctant Freud fled to Paris and then London with his wife and Anna.

Freud's ashes on display at Golders Green Crematorium, London
Freud's ashes on display at Golders Green Crematorium, London

8. Four of his sisters died in Nazi concentration camps.
Bonaparte attempted, but failed, to also obtain exit visas for four of Freud’s sisters. The psychoanalyst died just weeks after the launch of World War II. The four sisters left behind in Vienna were eventually sent to Nazi concentration camps, where they died.

9. Freud studied the sex lives of eels.
While enrolled at the University of Vienna, a young Freud studied zoology. On a research trip to Trieste to study the sexual organs of eels, his professor assigned him the task of finding the gonads of the male of the species, a discovery that had eluded scientists for centuries. Freud spent many hours dissecting eels to no avail. “All the eels I have cut open are of the tenderer sex,” he reported.

10. Thieves attempted to steal his ashes.
After Freud’s death, his ashes were placed in an ancient Greek urn given to him by Bonaparte. When his wife, Martha, passed away in 1951, her ashes were added to the vase stored at London’s Golders Green Crematorium. In January 2014, London police reported that thieves had attempted to swipe the Freuds’ ashes. Although the theft was thwarted, the thieves severely damaged the 2,300-year-old urn.