Probiotics are good bacteria found in yogurt and supplements. They can help your digestive health, but a new study has found they may also help combat depression and anxiety.

Two decades ago, Wendy Stuart's life came to a halt when she was diagnosed with chronic fatigue syndrome -- a puzzling illness that causes debilitating tiredness.

"I had to stop working and I really enjoyed my job, but I couldn't cope. I was so exhausted," she said. "I was unable to sleep at night, restless leg syndrome, brain fog where you being in the middle of a sentence and forgetting what you're saying."

Stuart also suffered from depression and stomach problems, which are common complaints of people with CFS.

It's a link researchers wanted to explore -- the relationship the gut has to the mind.

"About half [of those suffering from CFS] will meet the criteria for irritable bowel syndrome and they will also meet the criteria for anxiety and even depressive disorders," said Dr. Alan Logan, one of the co-authors of the study.

"There were some hints in experimental research and animal studies that probiotics, this is the bacteria you get in yoghurt, may actually influence mood," said Logan.

So Canadian researchers followed 39 patients with chronic fatigue syndrome.

"Half of them took a placebo powder, an inert, substance, and the other half took a probiotic," said Logan.

Those who took the probiotics saw their mood lift.

"They felt calmer -- they felt better able to cope with their illness, they were sleeping better, less heart palpitations, symptoms of anxiety," Dr. Allison Bested, another co-author

The researchers believe the bacteria help to produce feel-good chemicals in the brain -- while at the same time slowing down the production of undesirable chemicals. The findings could open the door to a new way of treating these mental disorders, but more studies need to be done.

"Now it is time to dig deeper and really get into this with patients with actual depression and anxiety and see what happens from there," Logan said.

Stuart is still taking probiotics daily and says it's made a difference when other medications failed.

"A lot of the brain fog lifted, I felt better on it... it was really beneficial," she said.