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.

According to experts, nausea can make long-term illnesses worse for people who suffer from chronic conditions.

‘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

Many people with chronic illnesses will experience nausea.

Research has shown that 25% of pregnant women who experience severe nausea or vomiting while pregnant are affected by suicidal thinking.

According to Dr Adam Farmer (a consultant gastroenterologist at University Hospitals of North Midlands), chronic nausea is very common.

It can be caused by chemotherapy or 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.

In 2002, research published by General Hospital Psychiatry found that people with anxiety have three times the risk of long-term nausea than those without it. 

An explanation is that anxiety-related brain chemicals can disrupt the balance in bacteria within the stomach, leading to nausea.

Peter Whorwell, who is both a Wythenshawe Hospital physician and a professor of medicine in Manchester, said that chronic nausea could be related to psychological factors. He adds: ‘It’s a very challenging symptom to diagnose and treat as there are so many different potential causes.’

Recent research on women who experience hyperemesis Gravidarum (HG), which is excessive nausea or vomiting during pregnancy, provides stark evidence. 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.

Long-term effects can be felt even after symptoms subside. 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.

Although it is so common and can be quite disabling there aren’t any effective treatments. 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.

Professor Sanger says scientists are still unsure of what causes nausea.

He told Good Health: ‘We can now stop vomiting with drugs but you can be left with horrible inescapable nausea symptoms. Our belief was that vomiting could be stopped more easily than nausea. 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.

As a primitive response, this area coordinates nausea. The brain also communicates with the areas higher up, which includes the inner cortex. This is associated with fear and strong emotions.

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.

Professor Sanger headed a team of scientists that in 1980 created anti-sickness medicines for chemotherapy patients.

Patients stopped vomiting with the drugs by stopping the activity of 5-HT3, a receptor that is usually involved in the transfer of information through the stomach and control the wave-like effects of food and garbage.

The results came back 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.

According to him, olanzapine is an anti-psychotic that can offer some relief. ‘It affects about 12 brain receptors associated with nausea. However, it makes people feel sedated,’ he adds.

Anti-vomiting medications (also known as anti-emetic drugs) may be helpful in milder cases. These drugs disrupt signals traveling to and from the vomit center in the brain or slow down the contractions.

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.’

Lucy Elkins, Additional Reporting

Omega watch 

We all know omega-3 fatty acid are beneficial for our health. However, there are many other vital omegas. This week, Omega 9

These oils include avocado, olive and nut oils.

What to know: Animal studies suggest omega 9s increase ‘good’ cholesterol and are beneficial for the brain. 

In a 2015 study on mice, these fatty acids were shown to have an anti-inflammatory effect and to improve cells’ sensitivity to insulin, helping remove sugar from the bloodstream.