The future of depression treatment might be chilling in the dairy case. A study published this week in Nature Scientific Reports finds that beneficial bacteria commonly found in yogurt can help relieve depression-like symptoms in mice.

Over the last few decades, scientists have begun exploring the connections between our brains and all the microbes that live on and inside our bodies, and they've learned that those little microbes have an awful lot of power. Some studies have shown that bacterial imbalances can affect nervous system function, while others have suggested that people with bacterial imbalances may be more prone to anxiety and depression.

To test these hypotheses, researchers at the University of Virginia decided to begin at the overlap between the nervous system and mood: stress. Stress increases depression risk; it also affects, and is affected by, the function of the nervous system.

The scientists began by collecting a group of unlucky mice and subjecting them to a variety of intense stressors. Some were kept in crowded cages; others had to sit under strobe lights or listen to loud noises. Predictably, the stressful situations took a toll, and the mice began exhibiting what the researchers called “despair behavior.”

The researchers collected poop samples from the mice before and after the stress sessions, then ran genetic analyses to determine the species and quantities of bacteria living in each mouse’s gut. The results showed that the stress resulted in a pretty significant drop in a microbe called Lactobacillus—the same type of so-called "good" bacteria found in yogurt.

But the rodents’ despair would not prove permanent. The researchers began giving the mice small doses of Lactobacillus with their meals, and, over time, their symptoms resolved.

Lead author Alban Gaultier. Image Credit: Josh Barney | University of Virginia Health System

 
"This is the most consistent change we've seen across different experiments and different settings we call microbiome profiles," co-author Ioana Marin said in a statement. "This is a consistent change. We see Lactobacillus levels correlate directly with the behavior of these mice."

The team hopes to take their experiments into the human body next. Lead author Alban Gaultier said he has “big hope” that probiotics could someday augment or even replace side-effect–heavy antidepressant drugs. “It would be magical just to change your diet,” he said, “to change the bacteria you take, and fix your health—and your mood.”