Eating yogurt rich in lactobacillus -- a probiotic bacteria -- may help alleviate symptoms of depression and anxiety, a finding that could lead to new strategies for treating psychiatric conditions, researchers have found.

Depression is a huge problem and the treatments are not very good, because they come with huge side effects.

"The study will help us not to bother with complex drugs and side effects when we can just play with the microbiome. It would be magical just to change your diet, to change the bacteria you take, and fix your health -- and your mood," said lead researcher Alban Gaultier from the University of Virginia in the US.

In the study, conducted on mice, the researchers have discovered a specific mechanism for how the lactobacillus bacteria affect mood, providing a direct link between the health of the gut microbiome and mental health. 

For the study, published in the journal Scientific Reports, the team induced depression symptoms in mice to analyse their composition of the gut microbiome and found that the major change was the loss of lactobacillus. 

With the loss of lactobacillus came the onset of depression symptoms. Conversely, feeding the mice lactobacillus with their food returned them to almost normal, the researchers said. 

"A single strain of lactobacillus, is able to influence mood," Gaultier observed. 

In addition, the study found that the amount of lactobacillus in the gut affects the level of a metabolite in the blood -- called kynurenine -- which has been shown to drive depression.

When lactobacillus was diminished in the gut, the levels of kynurenine went up -- and depression symptoms set in.

While there is no harm in people with depression eating yogurt, people receiving treatment for depression should not stop taking their medications without consulting their physicians, the researchers suggested.

Based on the findings, the researchers plan to begin studying the effect in humans as soon as possible.