Grandiose delusion (GD) is a delusional belief about "having inflated worth, power, knowledge or a special identity which are firmly sustained despite undeniable evidence to the contrary" (APA, 2000 cited by Knowles et al., 2011). In a study of 1136 acutely hospitalized psychiatric patients, 29% were delusional: of those, 43% suffered from GD (12% of the total), and it was the most important delusion for 23% of delusional patients (6% of the total) (Appelbaum et al., 1999). In a British study of 20 GD patients (Smith et al., 2005), 7 had some sort of superpower (psychic, intellectual, physical), 5 were supernatural/religious beings (2 Gods, 1 Jesus, 1 prophet, 1 archangel), 3 were in relation with God, and 5 were VIPs: a queen, a gang leader in LA, a US admiral, the reincarnation of a historical figure, and Roger Taylor (from Queen). Two Gods were related to the British Royal family (one was the son of the late Prince Phillip) and one God-connected patient was Tony Blair's cousin (was/were = believed to be!).

The stereotypical depiction of the mentally ill person believing to be Napoleon has a simple explanation: this was a common occurrence in GD patients in the 19th century. Like today, GD sufferers believed to be celebrities, but only celebrities with an extraordinary, idealized symbolic value that overrides the actual person. Napoléon, Joan of Arc or Jesus Christ fitted that profile, but not the bourgeois King Louis-Philippe: in her study of the phenomenon, historian Laure Murat had not found a single patient in the French asylum archives who claimed to be him (Murat, 2014)...

Murat notes that the French revolution and the imperial period had been traumatic for the population, resulting in a rise in psychiatric patients with specific delusions, some linked with the guillotine. People believed that their head had been cut and replaced by someone else's. Philippe Pinel, a pioneer of French psychiatry in the late 18th and early 19th century, thought that "events connected with the Revolution" was causing an alleged epidemic of mental issues (cited by Murat, 2014).

There were two waves of Napoléon-themed GDs patients in French asylums. The first one took place after the fall of the Emperor. Murat:

In 1818 the Charenton asylum recorded the admission of just one son of Louis XVI (who also thought he was Jesus and the prophets Elijah and Samuel) compared with five Napoleons. One of the latter group “appointed” and “dismissed” legislators, another “had purchased Italy and conquered Asia,” yet another owned “forty thousand barrels filled with gold,” and so on. Five emperors out of ninety-two patients admitted that year represent 5.4 percent of the total madness at Charenton.

A second wave of Napoleon GDs happened after 1840, when Louis-Philippe organized the return of the Emperor's remains to France in a grandiose ceremony. In 1841–42, GD was diagnosed in over 25% of the men at Bicêtre and 10% of the women in La Salpêtrière. According to writer Alphonse Esquiros (1847), Dr. Voisin at the Bicêtre asylum recorded the admission of thirteen or fourteen emperors. Esquiros wrote:

This presence of Napoleon among us — all the images and external signs of the commemoration, which made his face spring up, so to speak, everywhere — indeed, everything about this event helped to create a particular cause of insanity.

It is important to note here that this took place at a time when psychiatry was nascent. Pinel, and his successor Jean-Étienne Esquirol, were introducing new concepts of mental illness and were trying to imagine ways to cure those disorders that were more humane and perhaps more efficient than physical restraints, bloodletting and cold showers. Esquirol catalogued what we call today GD under the umbrella of "monomania", with GD being the called monomanie ambitieuse, ambitious monomania, or sometimes monomanie orgueilleuse, prideful monomania. Pinel, Esquirol and their colleagues observed and listen to their patients, compiled information on them, drew them, and tested cures, including some based on discussing with the patients, something that was often feasible with the high-functioning sufferers of delusions (though cold showers were also in order when necessary, Estienne, 2010). The modern vision of the delusional patient dressed as Napoléon is directly linked to this emerging field of research.

The Napoléons observed by Pinel and Esquirol in Bicêtre, Charenton and La Salpétrière modelled their behaviour after the popular perception of the Emperor: authoritarian, capricious, irascible, belligerent, violent, and expecting to be obeyed. A medical report from 1831 found by Murat in the archives of the Charenton hospital reads as follows:

The first day we found him dressed elegantly, head held high with a proud, haughty air; his tone was that of command, and his least gestures indicated power and authority. He soon informed us that he was the emperor of France, with millions in riches, that Louis-Philippe was his chancellor, etc. Then, taking up a manuscript, he pompously recited verses of his own composition, in which he allocated kingdoms, settled the affairs of Belgium and Poland, etc. During the day he smashed everything because people would not obey his every order. He was calmed by a shower and then shut up in a cell. The next day we found him naked, having torn up everything, shouting, threatening, etc.

In another asylum, a former captain of the dragoon spent his time in a perpetual rage, insulting and striking people. Once, after being restrained by nurses, he complained that he, Napoléon, was treated in an undignified manner. "Those frightful valets bound me — I intend to have them shot." He only calmed down after the doctor told him that he was Napoléon indeed, but in Saint Helena.

Asylum Napoléons were usually men, but a couple were women. Murat found in the archives a 71-year old woman admitted in La Salpétrière in 1852 who said she was Napoléon. However, she was unable to tell which one, I or III, and could only say "Long live Napoléon". Napoléons, even female ones, were found outside France. In 1830, Dr Crawford at the Richmond Lunatic Asylum in Dublin reported the following (Combe, 1830):

Ann Kelly, aged 37. Two years ill. Monomania. Pride. Imagines she is Napoleon. Very irascible, but easily calmed by a little praise. Dresses partly as a man. Speaks of herself as a man, and in the third person. Has made herself trousers, and a highly-ornamented cloak with simple threads. Will never wear a cap.

(In the same asylum, Christopher Edmundson, aged 47, clerk, fancied himself Jesus Christ and attempted to walk on the sea and fast for forty days. He gave up his job to preach and work miracles.)

Other people believed to be related to Napoléon. One man found by Murat in the archives claimed to be Napoléon's son and mostly refused to talk to people. In 1897, a man standing in front of the entrance of the Charenton Asylum was threatening passer-bys with a knife. When the police arrested him, he claimed to be "the son of Napoléon I, a manufacturer of cotton tin hats [sic], the president of Crédit Foncier and of the Banque de France, and he could prove it". His "proof" was a torn-up saving books (Le Radical, 20 July 1897). In 1902, a young man was throwing stones at gas streetlights in Saint-Laurent-du-Pape (Southern France): when arrested, he justified his actions by saying that only electricity was worthy of France, and he said that he was Louis-Napoléon, the son of Napoléon III who had been killed by the Zulus in 1879. Authorities were unable to find his true identity so he was booked as Louis-Napoléon (Le Progrès de la Côte d'Or, 8 January 1902).

Some women thought that they were Napoléon's wife, not Joséphine or Marie-Louise, but a more powerful, or even superpowered, rival. One wealthy 46-year old woman claimed "to have the sun in her belly". As Napoléon's wife, she "ruled the universe thanks to electric fire in her body, which she could unleash at will" (cited by Murat).

The Napoléons were not limited to Europe. In 1911, the Duke of Morny, interviewed after a lunatic had tried to impersonate him, told that he had been contacted by a Napoléon living in the Lunatic Asylum of Québec, Canada: the man had granted him the title of Duke of the Berezina (Verneuil, 1911).

I have not found pictures of these Napoléons. However, an illustrated report by Dr Henri Dagonet from 1888 gives a few examples of what a Napoléon "megalomaniac" could look like and I have translated the written notes.

• Figure 1. Top left picture: Megalomania, proud attitude, haughty look, partial systematic delirium. The patient the patient is entrusted with a high mission, he is called to reform society; he knows all the sciences; he is the top genius in the world etc. [note the very Napoleonic attitude: hand in the vest and eyes fixed on the horizon]

• Figure 3 (same page as above). Bottom picture. Ambitious monomania, chronic megalomania. The patient covers himself with medals. His merits are exceptional; quiet, harmless, partial delirium.

• Woman in a man's suit. Aged 49. She changed her sex. She is the imperial prince. Her mother had a relation with Napoléon III. Napoléon IV having been killed by the Zulus, she is called to rule France. She is very annoyed when she has her period. One Mardi Gras and one Mid-Lent Thursday she dressed as a sailor and as a fireman. She sang and danced, being very happy in a man's costume. Very old delirium.

• And this happy fellow with a tricorn hat: Quiet, happy, chronic mania, extravagant actions.

Edit: GD numbers corrected thanks to u/memoryofthewaters (see their comment below).

->Continued