The plot keeps thickening when it comes to the connection between your gut and your brain.

A new review article links probiotics to changes in mood and mental health, suggesting these "good" bacteria might have potential as a treatment for depression and other psychiatric maladies. In the study, published in the journal Biological Psychiatry, researchers define the term “psychobiotic” as “a live organism that, when ingested in adequate amounts, produces a health benefit in patients suffering from psychiatric illness.”

(diditalbob8/flickr)

These organisms act on what researchers call the “brain-gut axis,” a biological network connecting the intestinal and endocrine systems to the spinal cord and regions in the brain that process stress, such as the HPA-axis.

Is all this plausible? Perhaps. Ghrelin, known as the “hunger hormone” and produced in the intestines, was recently found to play a role in the development of chronic stress. And stress in turn has been found to alter our microbiota. There's growing evidence that there's a special connection between the gut and the brain, and as one MGH psychiatrist said recently: “There is a neural feedback from the gut to the brain so chronic gastrointestinal distress can exacerbate anxiety or depression.”

Thomas Insel, Director of the National Institute of Mental Health, stated last December that how “differences in our microbial world influence the development of brain and behavior will be one of the great frontiers of clinical neuroscience in the next decade."

Dr. Timothy Dinan of University College Cork in Ireland and the psychobiotic study's lead author says that although the research conducted on humans is sparse, “the animal studies indicate that certain psychobiotics can change brain chemistry.”

In the review, a few of these psychobiotics and their effects on neurotransmitter production are listed:

Escherichia, Bacillus, and Saccharomyces produce norepinephrine. Candida, Streptococcus, Escherichia, and Enterococcus produce serotonin, while Bacillus and Serratia have the potential to produce dopamine.

As far as human studies are concerned, “if we find significant changes in the microbiota in conditions such as depression or schizophrenia, then normalizing the microbiota with psychobiotics may alleviate symptoms,” Dinan says. Placebo-controlled studies are up-and-coming in the U.S. and Europe, he adds, and if all goes well, “a product should be available within 5 years” for the “treatment of stress related disorders such as anxiety, depression, and irritable bowel syndrome.”