In 400 BC, the Greek physician Hippocrates wrote a treatise on epilepsy called On the Sacred Disease. At the time, epilepsy – a word from the Greek meaning ‘to seize, attack, take hold of’ – was widely believed to be caused by attacks from demons or gods. Hippocrates challenged this and proposed that the brain itself was the cause of the disorder, not invisible deities. Five hundred years later, Galen – now considered the greatest physician of the Roman Empire – agreed.
Yet Hippocrates and Galen were well ahead of their time in proposing that epilepsy was caused by physical abnormalities originating in the brain. The majority of physicians and the general public believed that it was caused by supernatural interventions, sexual activity such as masturbation, and these beliefs persisted well into the nineteenth century. In fact, of all neurological diseases, epilepsy is the one that has been most frequently linked to sex. One influential medical voice on this topic was the famous Swiss physician Samuel-Auguste Tissot, who argued that excessive masturbation could cause epilepsy. He published a book in French in 1760 called L’Onanisme, translated into English as Onanism: Or a treatise upon the disorders produced by masturbation. (I was amazed to find you can still buy a paperback copy through Amazon.) At the time, castration and clitoridectomy (removal of the clitoris) were reportedly performed on people with severe epilepsy.
The supposed link between epilepsy and sex continued into the next century when neurologist Edward Sieveking emphasised sexual disturbances as a leading cause. In his book On Epilepsy and Epileptiform Seizures, published in 1858, he stated that although he believed hereditary factors played a role in the disease, ‘the unanimous consent of all writers on epilepsy demonstrates the truth of the statement that in this disease, the sexual organs are very frequently at fault’. He cited an ancient proverb attributed to Galen, ‘Coitus brevis epilepsia est’ – ‘Sex is a brief seizure’, and argued that sexual derangement ‘enfeebled the system, and by producing excitability gives rise to the epileptic paroxysm’. Sieveking regarded masturbation as a specific cause of seizures, and wrote that in nine of the 52 people he had treated for epilepsy, ‘the sexual system was in a state of great excitement, owing to recent or former masturbation’.
I was surprised to learn that Sieveking had been a physician at the National Hospital for Neurology and Neurosurgery in London in 1864. I worked at the same place over 150 years later. It was where I’d assessed Jack, the man exhibiting hypersexuality after a fall from scaffolding, described in Chapter 2. I knew that many renowned neurologists had worked there, including John Hughlings Jackson (1835–1911), often referred to as ‘the father of English neurology and modern epileptology’, and William Gowers (1845–1915). Neither of these influential neurologists considered sex the origin of epilepsy. Rather, they identified neurophysiological causes and laid the foundations for current views of the aetiology of epilepsy.
Yet while the notion that sex causes epilepsy has been well and truly debunked, it is widely accepted and scientifically proven that sex can actually trigger some brain conditions. These dramatic brain disorders can be temporary, as in the case of transient global amnesia, or can cause permanent brain damage, such as the rupture of a brain aneurysm. In the rare cases where these conditions are sex-induced, it seems it is the dramatic blood flow changes in the brain that occur during sex that are to blame.
‘WHERE AM I?’ SARAH MUMBLED.
Joe laughed. Sarah had a quirky sense of humour and he thought she was joking. He had his eyes closed and had been enjoying a post-sex snooze. He ran his fingers along her thigh and replied, ‘You’re a funny one.’
‘Where am I? Why am I here?’ she asked, louder this time and more insistently.
Joe laughed again. ‘What are you playing at, you cheeky thing?’
It wasn’t until she asked a third time, and he heard the tremor in her voice, that he realised it wasn’t a joke. She was genuinely frightened. ‘What’s happened? Where am I?’
Joe rolled on his side to face her. Sarah was staring at the ceiling. Tears were trickling down the side of her cheek, forming a wet patch on the pillow beside her face.
‘Sarah, you’re in bed. What’s wrong? Why do you keep saying that? What’s going on?’
‘Why am I here?’
They had just had sex – very successful sex, Joe felt, given that she’d had an orgasm for the first time in months. He felt proud that he still had the knack to get her there. But his post-sex pride was quickly evaporating and being replaced by worry. He put his hands on her cheeks and touched his nose to hers. Then he pulled back and stared into her eyes.
‘Darling, you’re at home in bed with me. Are you feeling OK?’
Sarah looked at him blankly, and when she said exactly the same words again, he became frightened. Was she having some kind of stroke? He tried to think back to his first aid training at work. What was the acronym you had to run through for stroke? Something about asymmetry and paralysis? He checked her face again and she looked fine, apart from the confusion in her eyes. He told her to move her arms and legs and asked if they felt normal.
‘They feel fine,’ she replied, ‘but where am I?’
Joe was perplexed. ‘Why do you keep asking me that?’
He felt sick. ‘Just wait here, darling. I’ll be back in a minute.’ He grabbed his phone off the bedside table, pulled his dressing gown on and rang an ambulance.
Transient global amnesia is a sudden and temporary impairment of memory during which a person cannot learn or recall new information (anterograde amnesia) and may also have difficulty recalling old memories (retrograde amnesia). During transient global amnesia the person remains alert and aware of their personal identity and is able to communicate. The main symptoms are repetitive questioning and disorientation. It typically occurs as a single episode and is considered a ‘benign’ disorder, as the memory problems completely resolve within 24 hours and there are no long-term effects. In the case of Sarah, she was back to her usual self the next day, and eventually her and Joe were able to laugh about the time their sex was so good she ‘lost her mind’.
Many people have learned about amnesia from characters in films such as 50 First Dates (2004) and Eternal Sunshine of the Spotless Mind (2004). Although entertaining, ‘cinematic amnesia’ is usually not realistic. In an article in The British Medical Journal, neuropsychologist Sallie Blaxendale summarised ‘amnesia in the movies’, and pointed out the many myths that are perpetuated on screen. For example, characters with amnesia have often suffered a head injury that has caused them to forget who they are (loss of identity) and lose memories of their whole life before their injury (retrograde amnesia), but they have no difficulty learning and recalling new things after their injury. In reality, extensive retrograde amnesia and loss of identity are rare and typically suggest a psychological cause rather than a brain injury. The more typical type of amnesia after a brain injury involves difficulty learning and recalling new things (anterograde amnesia). It is also common in movies for a second head injury to cure the character of their memory loss, which never occurs in reality.
An accurate cinematic portrayal of amnesia, however, is found in the film Memento (2000), in which the character Leonard has a very realistic amnesia after a head injury. He retains his identity but has significant anterograde amnesia, to the degree that he tattoos crucial new information on his body to aid his memory. In fact, the animated fish Dory from the children’s films Finding Nemo (2003) and Finding Dory (2016) has another of the most neuropsychologically accurate portrayals of amnesia ever seen on screen. I don’t know of any films that feature a character who experiences an accurate transient global amnesia, but there would be no need to exaggerate. Even a realistic portrayal of this bizarre condition would be riveting.
Although there have been hundreds of reported cases of transient global amnesia in the medical literature, its cause is still unknown, and it is regarded as one of the most mysterious of all the neurological conditions. A common risk factor is a history of migraines. Various triggers have been reported, including strenuous physical activity, emotionally arousing or stressful events, a sudden change in body temperature, and – yes – sex.
In a study that specifically explored what triggered transient global amnesia, sex was the most common precipitant in the 21 cases studied, reported by one-third of the subjects. Interestingly, this same study distinguished between sex that was ‘conjugal’ (within a married or established couple) or ‘extra conjugal’ (outside of a marriage or relationship – in other words, during an affair), and noted that being unfaithful could be considered a ‘stressful situation’; it had been reported in several transient global amnesia cases. Sex ticks two of the boxes of the known triggers for this type of amnesia: it can be both physically strenuous and emotionally arousing. This is particularly so if the sex is with someone who is not your usual partner, as in the case of Roger.
Roger was 46 years old, a successful, hard-working architect and teacher. He was prone to self-doubt and anxiety, and had experienced panic attacks in his twenties. He felt stressed and overworked, and when his boss put him in charge of a large architectural project, he complained to his wife that he wished he could retire. He also started to exhibit more aggressive, erratic behaviour. When someone backed into his car in a parking area he exploded, gesturing wildly and screaming when the other driver approached him to apologise. One day he argued with the students in his architecture class, stormed out of the classroom and drove home to have lunch with his wife. After lunch, he told her he was going back to the office but he lied. He was actually going to visit his lover, who he had been secretly seeing for over a year. He felt he deserved some joy in his life, and it had been weeks since he had seen her. As he drove into her driveway, his stress slowly evaporated and was replaced with excitement. He felt like he was 17 years old again. They had frantic sex, like teenagers who were afraid of getting caught by their parents.
Afterwards, Roger couldn’t recognise his own pants that were draped across a chair, and struggled to recall what he had done that morning. He eventually got his clothes on and was able to drive home. His wife noticed immediately that something was unusual about him. He was vague, and kept repeating the same questions, not seeming to recall her answers. She took him to the emergency department of their local hospital. He was seen by a neurologist and all the investigations came up as normal. He was diagnosed with transient global amnesia, given a sedative and admitted to hospital for the night. When he awoke the next morning, he had fully recovered. We don’t know if he ever told his wife about his affair, or if he ever visited his lover again.
AN ORGASM IS A UNIQUE EXPERIENCE FOR YOUR BODY and, of course, for your brain. It is considered the peak or ‘climax’ of sexual experience and is associated with specific physical and psychological changes. These changes were first documented by William Masters and Virginia Johnson, groundbreaking sex researchers at Washington University in the United States. In the late 1950s, they conducted a series of experiments to document the physiological changes that occur during sexual activity. The TV series Masters of Sex portrays their revolutionary research, which initially faced many barriers. In a scene from the pilot episode, Masters presents his proposal to study what happens to the body during sex to his boss at the hospital where he works as an obstetrician and gynaecologist. His boss tells him he is jeopardising his career to study such a risky subject. ‘It’s smut, Bill,’ he tells Masters, adding that the hospital board will label his proposal as ‘pornography or prostitution or something equally depraved’. The study ‘will never be seen as serious science,’ he adds, ‘and you will be labelled a pervert’. Masters laments the lack of support in an eloquent monologue:
Every museum in the world is filled with art created from this basic impulse – the greatest literature, the most beautiful music. The study of sex is the study of the beginning of all life, and science holds the key. Yet we sit huddled in the dark like prudish cavemen, filled with shame and guilt, when the truth is: nobody understands sex.
Some of this context represents creative licence on the part of the series’ producers, but in reality Masters and Johnson persisted with their novel research studies, which involved directly observing people masturbating, or having sex with randomly assigned partners, while wired up to various monitors to measure things like heart rate and skin conductance. Some participants even had a camera inserted intravaginally to photograph changes that occurred within the vagina during orgasm. Masters and Johnson participated in the study themselves; they became lovers and eventually married.
Masters and Johnson outlined a ‘sexual response cycle’ that comprises four distinct phases: (1) excitement, an initial state of arousal that involves increased heart rate, blood pressure and muscle tone (tightening of muscles); (2) plateau, or full arousal, which immediately precedes orgasm and is associated with a further increase in muscle tone, heart rate, blood pressure and breathing rate; (3) orgasm, or sexual climax, during which the muscles spasm, and heart rate, respiratory rate and blood pressure all peak; and (4) resolution, which involves the normalisation of all the physiological changes associated with orgasm. More recently, researchers have criticised Masters and Johnson’s model for its failure to consider psychological, relationship and cultural factors, and for its assumption that people progress from one phase to the next in succession, which may not be the case. Other researchers have also revised the sexual response cycle. For example, an additional phase of ‘desire’ was introduced in the late 1970s by sex therapist Helen Singer Kaplan, who proposed a three-phase model of desire, excitement and orgasm. Our understanding of the human sexual response, however, is still largely thanks to Masters and Johnson’s trailblazing work. Despite the criticisms and variations proposed in alternative models, there is no disputing the fact that an orgasm is widely regarded as the peak of human sexual experience.
Masters and Johnson were more interested in the physical responses that occurred during sex than what went on in the brain, but they did use scalp EEG – where electrodes are placed on the scalps of participants – in their experiments, which would have provided them with crude measurements of the brain’s electrical activity. Nevertheless, this method is plagued with problems, such as the disruption of measurements by body movements, and later studies have found no specific changes in scalp EEG measurements during orgasm. The advances in neuroimaging technologies since Masters and Johnson’s time now allow us to see what happens in the brain during orgasm, and several studies have examined this very issue. The brave participants in these studies have managed to have an orgasm, either self-stimulated or with a partner, while lying in the claustrophobic tunnel of an MRI machine or PET scanner, being observed by scientists and technicians as the patterns of blood flow and glucose metabolism in their brains are recorded – all for the sake of science. Most studies of orgasm in men have used PET scanning, which has the limitation of acquiring data over one to two minutes; this is too long to capture the relatively short event of ejaculation, and means that the brain imaging findings relate to events that occur immediately before and after orgasm (such as high sexual arousal and sexual satisfaction post-orgasm). Nevertheless, some studies of both men and women have documented a deactivation of prefrontal brain regions during orgasm, interpreted as the disinhibition or ‘lack of control’ required for orgasm to actually occur, while more recent studies have found activation of these brain regions in the lead-up to and during orgasm (see Chapter 2). These differences in findings are thought to be due to methodological variations in neuroimaging methods, and whether the orgasm was self-induced or via partner stimulation. There is still more work to be done to fully understand the neural correlates of human orgasm.
I spoke with the only researcher in the world who is currently doing empirical studies of the physiology of human orgasm. Dr Nicole Prause is a psychologist, neuroscientist and sex researcher who started studying the psychophysiology of sexual behaviour when she was an undergraduate student at Indiana University, where the famous Kinsey Institute is based. She uses various standard psychophysiological measures, such as skin conductance and heart rate monitors, in addition to her purposefully designed anal probe to measure contractions during female orgasms. She is currently working on a wireless intravaginal device. ‘I never have any problem recruiting participants for my studies. People love them! The only exception is that they don’t like the anal probe. If they don’t want to come in, that’s usually why.’
Despite sticking with the topic of sex for her entire research career, she admitted that the focus comes with some drawbacks. ‘In hindsight, I would not have focused so much on sexuality, because the controversy around it really has been a career struggle. But the area is obviously fascinating, and it comes with a balance of fun and controversy. It lets you be cutting edge when others are too chicken to do it.’ It is clear from Nicole’s experiences that the stigma and controversy around human sexuality research remains strong. Masters and Johnson struggled with institutional constraints in their sex research more than 60 years ago, and yet Nicole is still facing the same battles. ‘There’s a reason other people aren’t doing it. There’s challenges with getting grant funding, and even when you get it, sometimes Congress rescind the funding from scientists studying this stuff.’
In the early 2010s, when Nicole was a research scientist in the Department of Psychiatry at UCLA, she applied to the ethics board to do a research study on female orgasm. The board would not approve the study. When she was awarded a grant from a non-profit organisation to study ‘orgasmic meditation’ in couples and the university would not allow her to accept it, she realised she had to leave the university if she wanted to continue in the field: ‘Clearly this research cannot be done at a US university campus – it’s just too controversial!’ So, out of necessity, Nicole started her own research lab, Liberos, where she currently conducts her own studies, free of the hassles of university administration. She currently collaborates with other academics from various universities. ‘This works really well,’ she said. ‘It means their universities can outsource the controversy to me.’
Nicole told me that there is very limited knowledge about basic orgasm physiology, particularly in women. Half her female sample in a recent study self-reported having an orgasm but didn’t actually show the physiological response of contractions that accompany orgasm. She doesn’t know what to make of this and wishes there was more understanding ‘just about the basics of orgasm’.
To avoid some of the limitations of early scalp EEG technology, Nicole uses more modern EEG technologies in her studies to look at brain responses during orgasm. She said EEG is useful because of its speed, as you only get one trial with orgasm research. ‘I’m only able to do it because of the new bluetooth EEG headsets, as they allow movement.’ The trade-off, she said, is that ‘you can’t do localisation’, which would identify the specific brain regions the electrical changes occur in: ‘You can only really look at the whole brain response.’ Obviously people move quite a bit when they masturbate and orgasm, so the old ‘bite bar’ to help subjects keep their heads still is not an option. Her research group attaches an accelerator to the back of their heads to monitor movement, so this can be mathematically removed from the data for analyses.
She told me about some interesting EEG results from her research on female orgasm. Women are given an hour to reach orgasm in the lab. Nicole has found that just before her subjects are told that ‘they can go for it’, they show a strong suppression of alpha wave activity, a type of electrical brain activity that you see when people are awake and alert. They also show an increasing galvanic skin response, which is a measure of sweat on the skin; an increase is associated with emotional arousal. But then something intriguing happens: ‘As soon as they are told they can go for it, this flips – we see a precipitous drop in galvanic skin response, and an increase in alpha activity.’ I ask Nicole why she thinks that’s the case:
What we think is happening is that you need to reduce neural inhibition to allow enough synchronous neural firing in order to trigger a climax, or to trigger whatever it is that triggers an orgasm. We still don’t actually know what that is, but we think it might be similar to some seizure disorders, and that there has to be some amount of synchronous neural firing to allow the rhythmic muscle contractions to occur in the pelvis. There’s probably a need to release neural control to allow orgasm to occur.
I was surprised to hear yet another link between sex and seizures! Nicole’s interpretation of her EEG results echoes some previous neuroimaging findings of deactivation of prefrontal brain regions during orgasm. Her study is currently under peer review and yet to be published, but it will no doubt make an important contribution to the scarcely researched topic of the neuroscience of female orgasm.
Nicole feels it’s important to emphasise the broader implications of sex research. ‘Sex research is never going to be important for those people who think sex is only for procreation,’ she pointed out. ‘We need to show it has a health application.’ She is exploring how orgasm can be used to facilitate sleep, and how work productivity may be related to sex, by doing cognitive tests with her participants before and after their orgasm or sex research sessions. Is it reasonable to masturbate at work if it means you’ll be more productive after it? Grant funders and university ethics committees might not care about the intensity of orgasms, but if sex research can be related to these broader implications for health and productivity, the path to getting this research done may be a lot smoother in the future.
AS WE HAVE SEEN, THE SUDDEN BLOOD FLOW CHANGES that occur in the brain during orgasm can occasionally trigger an episode of transient global amnesia. There are also other neurological events that can be triggered by sex. Sex can induce seizures (see Chapter 2) and even stroke. If you are unlucky enough to have a brain aneurysm, a malformation that looks like a small balloon protruding out the side of a blood vessel in your brain, intense physical activity such as sex (especially with an orgasm) can cause the aneurysm to rupture or burst. A ruptured brain aneurysm can result in blood leaking into your brain, which is called an intracranial haemorrhage and is a type of stroke, or it can cause a subarachnoid haemorrhage, which means that the blood has leaked under the arachnoid mater, one of three membranes that covers the brain.
A brain aneurysm can grow anywhere within the blood vessels of your brain, and the effects of a ruptured aneurysm depend on where it is located. Why they appear is unknown, but certain risk factors such as smoking, high blood pressure, and heavy alcohol or cocaine use can increase your chances of growing a brain aneurysm. Sometimes it is just the luck of the draw of inherited genetic conditions. They are more common in women than men. It is estimated that one in 50 people have an unruptured brain aneurysm, and most people would not even know they have one – they are most often discovered incidentally during a brain scan in search of other conditions. Treatment of an unruptured brain aneurysm to prevent it from rupturing and bleeding involves ‘clipping’ (where the blood vessel under the aneurysm is clipped), endovascular treatments (coiling, stents or flow diversion), or just leaving it alone and monitoring it over time. A ruptured brain aneurysm causes death in 40 per cent of cases; of those who survive, two-thirds end up with a neurological deficit. This is what happened to Samantha.
Sociable 25-year-old Samantha had no history of psychiatric illness. Considered a ‘party animal’ in her circle of friends, she had drunk alcohol heavily since her teenage years. Her friends described her as ‘impulsive’, ‘promiscuous’ and always popular with the boys, but she had eventually settled into a relationship with Cameron, her on-again-off-again boyfriend of seven years, and they planned to marry. One evening, while having sex, Samantha suddenly developed an extremely severe headache, nausea and vomiting. She was found to have a haematoma – a bleed – in her right temporal lobe from an arteriovenous malformation (AVM), a tangle of abnormally formed blood vessels that are prone to bleed. A neurosurgeon operated on her to evacuate the blood and remove the AVM. After the surgery she had left-sided hemiparesis (weakness on the entire left side of her body) and a left homonymous hemianopia (impaired vision in her left visual field).
Three months after her surgery, Samantha developed seizures that arose from her right temporal lobe; these can occur after a bleed in the brain – an intracranial haemorrhage – due to the blood causing scarring of brain tissue. Her behaviour also changed, and she was described as ‘bizarre’ and ‘not her normal self’. She became ‘a nuisance to her neighbours’ and would collapse in their doorways; she was aggressive towards her mother, who struggled to care for her. She frequently turned up at the emergency department of her local hospital claiming to have had another brain haemorrhage. Cameron couldn’t cope with this new Samantha and left her.
Samantha had had the disastrous experience of a sex-induced ruptured AVM, which was followed by seizures arising from her right temporal lobe – and, as we know, this is a crucial part of the sexual neural network (see Chapter 1). Her neurological condition later deteriorated further when she developed erotomania, a love delusion, as we will see in the next chapter.
So, if you have a brain aneurysm, how likely is it that having sex will cause it to burst? One study estimated that intense physical activity such as sex can make an aneurysm up to 15 times more likely to rupture. Case studies have reported that sex was the immediate preceding activity before a ruptured aneurysm in up to 14 per cent of patients, and this is much more common in men (33 per cent) compared to women (7 per cent). This gender difference is a surprise: brain aneurysms are actually more common in women, and women have longer orgasms than men. It has been proposed that the higher risk of sex-induced subarachnoid haemorrhage due to ruptured aneurysm in men is due to the greater increase in arterial blood pressure that they experience during sex.
How can sex cause a brain aneurysm to burst? The two key factors that make brain aneurysms rupture are increases in blood pressure and a sudden reduction in intracranial pressure. This is exactly what occurs during sexual activity, particularly in the late plateau and orgasm phases of the human sexual response cycle outlined by Masters and Johnson. The profound changes in blood pressure, heart and respiratory rate, and muscle tension that accompany these sexual response phases result in increasing pressure on the wall of the aneurysm, making it more likely to burst. This is a highly dangerous event; many die before reaching hospital and there is significant disability in the majority of survivors. When it is triggered by sex, it turns out that sudden death is much more likely if you are having sex with someone who is not your usual partner. In other words, the excitement of extra-marital or ‘unfaithful’ sex in an unfamiliar environment is associated with more intense cardiovascular changes (that is, to heart rate and breathing rate) than those that occur during sex with your long-term partner in your bed at home. Heavy food and alcohol intake are also associated with increased blood pressure and the risk of ruptured brain aneurysm. So, if you have a brain aneurysm, think twice before booking that fancy restaurant and hotel room for a fling. Sticking with your current partner might just save your life.
To answer the question posed in the title of this chapter, yes, sex can actually trigger a dramatic change in your brain, and on rare occasions can even damage your brain. Where you have sex, who you have it with and whether you reach orgasm all have an impact on exactly what happens in your brain. These are fascinating observations that raise more questions than answers.