Scientists have been increasingly discovering how our gut bacteria affect health, and how a poop transplant to modify those gut bacteria can be a viable form of treatment. Now there's new evidence that this kind of procedure can even fix a particular psychiatric problem.

In a study of 20 patients with liver cirrhosis and hepatic encephalopathy (HE) – brain issues that often go alongside cirrhosis – the 10 patients given a faecal microbiota transplantation (FMT) saw sustained improvements in cognitive health.

Hepatic encephalopathy develops in more than 40 percent of people with liver cirrhosis, and can cause problems with thinking, changes in personality, confusion, and forgetfulness, though symptoms can vary in their severity.

Over the course of five months, HE patients who had been given the transplant were reporting fewer episodes and hospitalisations than those receiving standard treatment, and that's a promising development for this type of transplant.

"We believe it confirms that FMT from a rationally selected donor was safe and associated with substantial long-term improvements in both clinical and cognitive outcomes in patients with cirrhosis and recurrent HE," says one of the researchers, Jasmohan Bajaj from Virginia Commonwealth University.

"These findings now need to be confirmed in a larger patient population."

The brain damage the condition causes is sometimes irreversible, and in the worst cases, those with HE can slip into a coma and die.

It's thought that a build up of toxins that the liver would normally remove leads to HE, and this is the way the researchers decided to tackle it.

In particular, they wanted to add the beneficial Lachnospiraceae and Ruminococcaceae microbes, and remove the potentially poisonous Enterobacteriaceae bacteria from the gut – all of which have been linked to HE in the past.

The trial run was made possible by a poop specimen identified at a donor bank - it matched the bacterial composition the study team was looking for, so they could prepare a batch of treatments.

While this is a small study of only 20 people, the researchers concluded that this type of treatment is indeed safe and can be beneficial in the long term, helping to cut down on the toxins that would otherwise lead to HE developing further.

Scientists are continuing to probe the relationship between gut bacteria and our brains, with evidence of two-way interactions that can affect health and well-being. What's more, bacteria is being linked to a growing number of brain conditions, including Parkinson's.

As this work progresses, we might be able to add HE to the list of brain problems that can be tackled through the gut – and a careful mixture of faeces.

"Hepatic encephalopathy is a debilitating condition and a major burden to patients and caregivers, and new therapies are urgently needed," says hepatologist Annalisa Berzigotti from the University of Bern in Switzerland, who wasn't involved in the research.

"This study provides an important piece of evidence. The encouraging long-term results of FMT in HE strongly support the need for a larger, multicentre study of this intervention."

The research has just been presented at the International Liver Congress 2018 conference.