Feeling overwhelmed by the sensation that you’re going to be sick is one of the most miserably debilitating experiences — pity, then, people who live with nausea, feeling severely sick for days, weeks, even months on end.
Experts say that for many people living with long-term conditions, the nausea this causes can be the worst part of their illness.
‘It is so debilitating that it stops people living their daily lives,’ says Gareth Sanger, a professor of neuropharmacology at the Blizard Institute at Barts and The London School of Medicine and Dentistry.
‘Research has found that patients are so desperate to escape chronic nausea that they say they would even be prepared to gamble on taking a theoretical pill that would have a 50/50 chance of curing them or killing them. It’s that bad.’
Experts say that for many people living with long-term conditions, the nausea this causes can be the worst part of their illness
Recent research found that a quarter of women affected by severe, persistent nausea and vomiting during pregnancy suffered suicidal thoughts as a result.
Chronic nausea is common, with as many as one in eight people suffering from it on a regular basis, and many more affected intermittently, according to experts including Dr Adam Farmer, a consultant gastroenterologist at the University Hospitals of North Midlands.
The causes range from chemotherapy to persistent stomach conditions (such as chronic indigestion). But it can also be a long-term effect of the winter vomiting virus and, more surprisingly, is linked to anxiety and depression — with at least one study suggesting that these conditions are such common triggers that patients should be checked for them before being sent for invasive tests for possible gastric causes.
Research published in General Hospital Psychiatry in 2002 found that patients with anxiety are three times more likely to suffer long-term nausea than people without the condition.
One theory is that brain chemicals released as a result of anxiety disrupt the balance of bacteria in the gut, with the knock-on effect of causing nausea.
Yet precisely because chronic nausea can be linked to psychological factors, it is sometimes not rigorously investigated, says Peter Whorwell, a gastroenterologist at the Wythenshawe Hospital and professor of medicine at the University of Manchester. He adds: ‘It’s a very challenging symptom to diagnose and treat as there are so many different potential causes.’
Stark evidence of its harrowing effects emerged in a recent survey of women with hyperemesis gravidarum (HG), excessive nausea and vomiting in pregnancy. As well as revealing that a significant proportion of these women had suicidal thoughts, it found that 5 per cent said they’d terminated their pregnancies because of the condition, reported the journal Obstetric Medicine.
As many as 3.6 per cent of pregnancies are affected by HG — Kate Middleton, the Duchess of Cambridge, famously suffered it while carrying all three of her children.
The impact of such prolonged nausea can persist long after the sensations have abated. Nearly 30 per cent of women with HG suffered postnatal depression compared with 7 per cent of women who didn’t have HG, according to a study of more than 200 mothers published last year in the journal BMJ Open by researchers from Imperial College London.
Despite being so prevalent and disabling, there are no reliable treatments for HG-induced nausea. Professor Catherine Williamson from King’s College London, who led the latest HG study, says there is an ‘urgent need’ for further research into its causes.
‘By answering these questions, we will be able to develop more effective treatments,’ she says.
The problem is that scientists still know very little about what actually causes nausea, says Professor Sanger.
He told Good Health: ‘We can now stop vomiting with drugs but you can be left with horrible inescapable nausea symptoms. We thought that nausea would be easier to stop than vomiting. The reverse has proved true.’
While vomiting is a physical action involving muscle and gut convulsions, nausea is a sensation created by the nervous system and brain — and ‘science is still right down at the bottom rung of researching this’, he says.
‘What is known is that nausea sensations originate in the lower, most primitive part of our brains,’ he explains, referring to the brainstem at the bottom of the organ.
An area in the brainstem called the medulla oblongata receives sensory input from the rest of the body for causing feelings of nausea — these include motion that may cause travel sickness, and sickness from gut infections.
This area co-ordinates the physical act of vomiting as a primitive response to food poisoning, for instance. It also sends signals into areas of the higher part of the brain, including the insular cortex (associated with strong emotions such as fear), which generate the actual sensations of nausea.
One of the problems with ‘curing’ nausea is that the mechanism is protective — it evolved to stop us taking too much of something that could harm us.
Back in the 1980s, Professor Sanger led a team that created the first anti-sickness drugs for cancer patients who were undergoing chemotherapy.
The drugs stopped the patients vomiting by halting the action of a receptor called 5-HT3, which is normally involved in transferring information along the gut and controlling the wave-like actions of food and waste through it.
But the results were disappointing. ‘We thought that if we stopped the vomiting, then nausea would also be stopped,’ says Professor Sanger. ‘But the nausea was left behind unaffected.’ Some people are more prone to nausea than others. For example, women who vomit in the first trimester of pregnancy are more likely to vomit if they are given chemotherapy, while the under-50s are also more prone to experience nausea from chemotherapy — but the explanation for this is not clear.
Women are also more prone to cyclical vomiting syndrome — a rare condition which causes sufferers to be sick multiple times a day. ‘Without treatment they can die, as the repeated vomiting can deplete their levels of electrolytes [salts and minerals], and if potassium levels in particular drop too much your heart stops,’ says Professor Whorwell.
Professor Sanger is leading a team that is studying whether nerve-related disruptions in the way the stomach contracts to digest food may cause chronic nausea in some people with upper-gut disorders, such as gastroparesis, a rare condition where the stomach doesn’t empty properly.
‘The stomach is paralysed — it’s not emptying properly and this triggers nausea and sickness,’ says Professor Whorwell.
The winter vomiting bug — norovirus — can also cause this stomach-paralysing effect and long-term symptoms in some people, he says.
‘The first thing that happens is your stomach stops emptying so well — it’s the virus’s way of trying to stay in the body as long as possible — and some people develop persistent symptoms,’ says Professor Whorwell.
The difficulty in developing new treatments for nausea and vomiting is ‘compounded by the fact that the lab creatures most used for drug development — mice and rats — have evolved not to vomit,’ says Professor Sanger.
He says that the anti-psychotic drug olanzapine can provide some relief. ‘It affects about 12 brain receptors associated with nausea. However, it makes people feel sedated,’ he adds.
Less severe cases may respond to anti-vomiting drugs (called anti-emetics) which disrupt the signals travelling to or from the vomit centre in the brain, or slow the contractions in the gut.
For chronic nausea that anti-emetic drugs don’t touch, doctors can suggest only self-help measures such as eating little and often and avoiding fatty foods, because these delay the emptying of the stomach.
Otherwise, as Professor Sanger says: ‘We can only wait, continue researching, and hope.’
Additional reporting: Lucy Elkins