‘It​ must be a full moon,’ colleagues remark when a night in the emergency department is particularly blood-soaked or there are an unusual number of psychiatric admissions. It’s an ancient and widespread belief that the moon has a transformative effect on the mind. A 1995 study in the US found that 40 per cent of the general public were convinced the moon had an influence on the mind; an earlier survey put the rate for mental health professionals at 74 per cent. But statisticians haven’t been able to substantiate the claim: the number of admissions for trauma, or for mania or psychosis (‘lunacy’), are unaffected by the phase of the moon, and there is no connection between a full moon and the frequency of suicide attempts, road accidents or calls to crisis support telephone services. My colleagues in emergency medicine, and those 74 per cent of American mental health professionals, are all wrong.

In a study from 1999 entitled ‘The Moon and Madness Reconsidered’, three Californian psychiatrists suggested that before the advent of effective artificial lighting in the 19th century, the full moon probably did affect those whose mental health was precarious, by depriving them of the sleep they needed. They cited evidence that resting in the dark for 14 hours a day can bring to an end or prevent episodes of manic psychosis, and that even a mild reduction in sleep duration can aggravate mental health problems or cause epileptic seizures – something patients of mine with bipolar illness and epilepsy have confirmed.

Before artificial lighting, people took advantage of the nights around a full moon. The light was powerful enough for them to be out and about. The Lunar Society of industrialists and intellectuals in 18th-century England named itself not for its object of study but because its members found it easier to meet on evenings when the moon was full. But moonlight was also shadowy enough to give a prompt to the fearful imagination. ‘The insane are more agitated at the full of the moon, as they are also at early dawn,’ the French psychiatrist Jean-Etienne Esquirol wrote: ‘Does not this brightness produce, in their habitations, an effect of light, which frightens one, rejoices another, and agitates all?’

Joanne Frederick​ was brought in by ambulance; ‘agitated delirium’ was written across the top of her triage sheet. The medical history came from her flatmate: she’d been suffering with a head cold for a few days, feeling weak and under the weather, and had gone to the pharmacy to buy medicine. It didn’t work: she became weaker, had abdominal pains, and her skin felt as if it was burning. Her urine felt hot, and was painful to pass. She’d had urinary infections in the past, but this was different: a bodily unease had possessed her, spreading up through her torso and out into her limbs. Her legs trembled, her arms lost all their power, and she had a persistent low-grade fever. She made an appointment to see her GP, but never made it: her flatmate called an ambulance when she began hallucinating giant lizards on the walls. On the way to hospital in the ambulance she had a seizure and when I met her in the high-dependency unit, she had been sedated.

There are hundreds of reasons someone might end up with an ‘agitated delirium’: drug overdoses, drug withdrawal, infections, strokes, brain haemorrhage, head injuries, psychiatric disorders, and even some vitamin deficiencies. But all of Joanne’s blood tests came back normal, and the CT scan of her brain was unremarkable. As she lay sedated in the high-dependency unit, her flatmate told me more of her story. Joanne lived a fairly quiet life, with a few close friends but keeping largely to herself. She’d been admitted to hospital with a ‘nervous breakdown’ once before; the hospital notes said she’d had a brief episode of incapacitating panic and anxiety that had resolved after a few days’ rest. She worked as an administrator in the basement of the city council offices – a job she liked because it allowed her to stay out of the sun. ‘She burns really easily,’ her flatmate said. ‘You should see her in the summer – she gets blisters from it.’ In places her skin was mottled with brown pigment, particularly across the face and hands.

I was a junior doctor at the time, and for me and the rest of the medical team Joanne’s diagnosis was a puzzle. When the supervising physician arrived to do his rounds he listened carefully to the story of how she came to be there, and flicked through the hospital notes from her previous admission. He examined her skin carefully, leafed through the reams of normal tests, then looked up with a glance of triumph: ‘We need to check her porphyrins,’ he said.

Porphyrins are critical for both animals and plants: in animals they support the molecular structure of haemoglobin, and in plants they do the same for chlorophyll. They are generated in the body by a series of specialised enzymes that work together like a team of scaffolders. If one of these scaffolders doesn’t work properly, porphyria is the result. Part-formed rings of defective porphyrin build up in the blood and tissues causing ‘crises’, which can be brought on by drugs, diet, or even a couple of nights of insomnia. Some porphyrins are extremely sensitive to light (it’s this property that enables chlorophyll to absorb the sun’s energy) and some types of porphyria lead to a blistering inflammation on exposure to the sun, leaving scars. The build-up of porphyrins in nerves and the brain causes numbness, paralysis, psychosis and seizures. Another, as yet unexplained, effect of the accumulation of porphyrins in the skin is growth of hair on the forehead and cheeks. Acute porphyria can cause constipation and agonising abdominal pain: it’s not unusual for victims to be brought howling into operating theatres, subjected to unnecessary operations time and again before doctors reach the correct diagnosis.

When Joanne’s lab report came back it confirmed soaring levels of porphyrins: it was likely that she had a variant of porphyria known as ‘variegate’. Treatment had already begun: rest, avoidance of exacerbating drugs (the cold remedies she’d bought over the counter had probably triggered her crisis) and intravenous fluids. To those we added infusions of glucose and some synthetic porphyrins. Within three days she had recovered, and was sent home armed with a list of drugs to avoid – and with an explanation, at last, of why she’d always been sensitive to light.

In​ 1964 a curious paper was published in the Proceedings of the Royal Society of Medicine by a London neurologist called Lee Illis. In four eloquent and persuasive pages he suggested that the werewolf myth had been reinforced or even initiated by porphyria. Skin conditions such as hypertrichosis may cause hair to grow over the face and hands, but have no psychiatric manifestations. Rabies in humans may induce an agitated, furious state of mind with biting and hallucinations, but without skin changes. Illis pointed out that people with porphyria avoid direct sunlight, and prefer to go about at night. Crises are precipitated by periods of poor sleep or a change in diet. In severe untreated cases sufferers may have pale, yellowish skin caused by jaundice, scarring of the skin, and hair may even begin to grow across their faces. People with certain types of porphyria may suffer derangements in their mental health and become socially isolated, breeding distrust in the wider community.

In past centuries this constellation of symptoms may have attracted accusations of witchcraft. A French exorcist, Henri Boguet, boasted in his Discours exécrable des sorciers (1602) of the number of werewolves and witches he had tortured and put to death: six hundred, including scores of children. ‘All these Sorcerers were grievously scratched on the face, arms and legs,’ he wrote. ‘One of them was so disfigured that he could scarcely be recognised as a human being, nor could anyone look at him without shuddering.’ It isn’t inconceivable that a light-sensitive, intermittent kind of madness, inflicted on an illiterate, isolated, credulous community, could raise the fear that human beings can transform into wolves. As the Enlightenment gained a foothold, ‘lycanthropy’ began to fade along with superstition (and the decline of the wolf population in Europe). But the delusion didn’t go away entirely: it just changed form. In 1954 Carl Jung described three sisters who dreamed night after night that their mother had transformed into an animal. He wasn’t surprised when, years later, the mother developed psychotic lycanthropy: the daughters, he reasoned, had unconsciously recognised their mother’s long repressed ‘primitive identity’.

One of the​ elm trees near my clinic seems to me different from all the others not because of its size, or the pattern of its limbs, but because one of my patients once fell twenty feet from it. Gary Hobbes wasn’t normally a tree-climber: he was a young man with schizophrenia who, after taking a cocktail of MDMA, became convinced he had transformed into a cat. Witnesses recounted that on the day of his fall he had been prowling the local streets examining the contents of bins, before scaling the elm to hiss at passers-by. The police were called; he climbed higher. A dog-walker approached to watch; Gary recoiled and screeched, demonstrating a previously unexpressed terror of dogs. The police were debating how to get him down when he slipped and fell, breaking his wrist on impact. He knocked his head too and lay mewling on the grass, concussed enough to be transferred to the emergency department.

The following morning Gary woke up on an orthopaedic ward with a plaster cast on his arm, reluctant to talk to the hospital psychiatrist. He was discharged back to his supported accommodation – a complex of small apartments with a warden on hand to help. On visits I’d see opened cat food tins in his kitchen and wonder if he might be eating them. From time to time I’d ask him about that night, but he changed the subject. The last I heard, he’d adopted a pair of street cats as pets, and had cat flaps put in the apartment door.

Psychiatrists have broadened the use of the term ‘lycanthropy’ to include any delusion of having been transformed into an animal, though the correct term is ‘therianthropy’, from the Greek ‘therion’: ‘beast’. In the late 1980s a group of psychiatrists in Massachusetts published a paper in which they described a series of 12 cases they’d seen over 14 years at a clinic in suburban Boston. Wolves were prominent: two had suffered true lycanthropy, two had become cats, two had become dogs, and two were ‘unspecified’ (their behaviour was ‘crawling, howling, hooting, clawing, stamping, defecating’, and ‘crawling, growling, barking’.) Of the remaining four cases, one had transformed into a tiger, one a rabbit, one a bird, and one – a lifetime keeper of gerbils – became his favourite pet.

There was no predominance of schizophrenia among the patients: eight were categorised as ‘bipolar’, two ‘schizophrenic’, one had a diagnosis of depression and one was described as having a ‘borderline personality’. There were no implications that things would get worse or last for a long time. ‘The presence of lycanthropy had no apparent relation to prognosis,’ the authors concluded. ‘The delusion of being transformed into an animal may bode no more ill than any other delusion.’ The most persistent transformation of all was of a man aged 24, who, following a period of alcohol abuse, became convinced, like Gary Hobbes, that he was a cat trapped inside a man’s body. At the time the series was published this man had lived in his feline persona uninterruptedly for 13 years. ‘The patient stated that he had known he was a cat since this secret was imparted to him by the family cat, who subsequently taught him “cat language”,’ the psychiatrists wrote. He held down a normal job, all the while ‘he lived with cats, had sexual activity with them, hunted with them, and frequented cat night spots in preference to their human equivalent.’ The psychiatrists had little hope for improvement – his belief had persisted despite various trials of antidepressants, anticonvulsants, antipsychotics and six years of psychotherapy. ‘His greatest – but unrequited – love was for a tigress in the local zoo,’ they concluded. ‘He hoped one day to release her.’

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Vol. 39 No. 23 · 30 November 2017

Gavin Francis is doubtful of claims that the full moon has an effect on human behaviour (LRB, 2 November). But while it is true that some studies have found no correlation, a number of others have done so. A German study from 2000 recorded a rise in binge-drinking ‘during the five-day full moon cycle’. Another, of inmates at a jail in Leeds in 1998, noticed a rise in violent incidents around the full moon. A doctor in Bournemouth claimed A&E calls went up by 3 per cent. A Swiss study from 2013 showed that sleep patterns were disturbed even when the subjects were unaware there was a full moon: ‘Volunteers spent 30 per cent less time in deep sleep, took five minutes longer to fall asleep, and slept for twenty minutes less.’

In 2007, the inspector responsible for co-ordinating policing in the so-called ‘marble’ area of Brighton, where the busiest clubs and pubs are located, compiled a graph showing an increase in violence around the time of the full moon. ‘The number of disturbances recorded increased significantly,’ he reported. ‘If you speak to ambulance staff, they will tell you exactly the same.’ He ordered Sussex Police to deploy extra officers at such times. (They no longer do so.) I live in the ‘marble’ area, and can confirm that it is often unnecessary to look out of the window to find out if there’s a full moon, especially at weekends. Ambient levels of noise – shouting, yelling, boom-cars, bongo-drumming, bottle-chucking, emergency sirens – increase noticeably.

Laurens van der Post, a wartime captive of the Japanese, recorded that he and his fellow prisoners dreaded full moons, which drew ‘a far tide of mythological frenzy’ in their captors’ blood. ‘Seven days, three days before and three days after and the day of the full moon itself, were always our days of greatest danger,’ he recalled, when sadistic beatings and beheadings tended to occur.

Graham Chainey

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