By Dr. Mercola

When it comes to your mental health, your behavior, and even your mood, we tend to think that the brain is in charge. In reality, your gut may be calling the shots. In the 1800s and early 1900s, it was thought that wastes in your colon could produce infections that lead to depression and psychosis.

Widely accepted for a time, mental-health patients were often treated with colonic purges and bowel surgeries, but eventually this was regarded as quackery.

Today, research is bearing out what the scientists of yesteryear were already privy to – that your mental health is very much dependent on the microbes in your gut. As Scientific American reported:1

In addition to the brain in your head, embedded in the wall of your gut is your enteric nervous system (ENS), which works both independently of and in conjunction with the brain in your head.

Your ENS contains 500 million neurons and is thought to be largely responsible for your "gut instincts," responding to environmental threats and sending information to your brain that affects your well-being.

This communication between your "two brains" runs both ways and is the pathway for how foods affect your mood.

For example, fatty foods make you feel good because fatty acids are detected by cell receptors in the lining of your gut, which then send warm and fuzzy nerve signals to your brain.

However, this gut-brain connection is far more than just comfort food or butterflies in your stomach. According to Scientific American:2

So-called germ-free mice, which have no microbiome to speak of, have altered behavior and brain function. In a study by John Cryan from the University College Cork in Ireland, mice without microbes in their intestines are unable to recognize other mice around them.

He believes that microbes may communicate with the brain and help us be social, which in turn allows the microbes to spread to others.3 In addition, mice lacking gut bacteria have been found to engage in "high-risk behavior," and this altered behavior was accompanied by neurochemical changes in the mouse brain.4

When examining the animals' brains, the researchers discovered a number of genetic alterations in the germ-free mice. According to The Guardian:5

Further, researchers have discovered that the absence or presence of gut microorganisms during infancy permanently alters gene expression. Through gene profiling, they were able to discern that absence of gut bacteria altered genes and signaling pathways involved in learning, memory, and motor control.

This suggests that gut bacteria are closely tied to early brain development and subsequent behavior.

These behavioral changes could be reversed as long as the mice were exposed to normal microorganisms early in life. But once the germ-free mice had reached adulthood, colonizing them with bacteria did not influence their behavior.6

Cryan believes beneficial microbes could one day be used to treat mental health problems in humans. He dubbed the compounds "psychobiotics." He told Scientific American:7

Interesting research led by microbiologist Premsyl Bercik and gastroenterologist Stephen Collins also found that when the intestines of germ-free mice were colonized with bacteria from other mice, they took on aspects of the donor's personality.8

Other research shows that women who had high prolonged fevers during pregnancy are more likely to have children with autism.

The finding held up in mice, too, and the MIA (maternal immune activation) mice were also found to have leaky intestines and abnormal microbiomes – a common occurrence in children with autism as well.9

Of particular importance, when the MIA mice were treated with a microbe called bacteroides fragilis, their gut permeability was corrected and many of their behavioral symptoms went away. According to the researchers:10

Research by pioneers such as Dr. Natasha Campbell-McBride also shows there's a profound dynamicinteraction between your gut, your brain, and your immune system.

She has developed what might be one of the most profoundly important treatment strategies for preventing and treating autism, as well as a wide range of other neurological, psychological, and autoimmune disorders—all of which are heavily influenced by your gut health.

Her findings show that children born with severely damaged gut flora are at a significantly increased risk of vaccine damage, which may help explain why some children develop symptoms of autism after receiving one or more childhood vaccinations while others do not.

Autismisn't the only potential outcome in this case. GAPS may manifest as a conglomerate of symptoms that can fit the diagnosis of either autism, or attention deficit hyperactivity disorder (ADHD), attention deficit disorder (ADD), dyslexia, dyspraxia, or obsessive-compulsive disorder, just to name a few possibilities.

Digestive issues, asthma, allergies, skin problems, and autoimmune disorders are also common outgrowths of GAPS, as it can present itself either psychologically or physiologically. It's critically important here to understand that the gut flora your child acquires during vaginal birth is dependent on your—the mother's—gut flora. So if your microflora is abnormal, your child's will be as well. Hence, addressing your gut health prior to, and during pregnancy, is essential.

The GAPS diet consists of easily-digestible foods that are dense in nutrition, including fermented foods. In general, avoiding processed foods and foods high in sugar/fructose is an essential component of a gut-healthy diet, as sugar feeds harmful bacteria and throws your microflora off kilter. For more information, please see my interview with Dr. Campbell-McBride, below.

Download Interview Transcript

The fact that this study showed any improvement at all is remarkable, considering they used commercial yogurt preparations that are notoriously unhealthy -- loaded with artificial sweeteners, colors, flavorings, and sugar. Most importantly, the vast majority of commercial yogurts have clinically insignificant levels of beneficial bacteria. Clearly, you would be far better off making your own yogurt from raw milk—especially if you're seeking to address depression through dietary interventions. Keep in mind that some signs of depression aren't widely known or may even be counterintuitive. Following are some of the more subtle signs of depression to keep an eye out for:12

✓ Aggression or hostility

✓ Irritability

✓ Withdrawing from those you love

✓ Extreme fatigue (mental and physical)

✓ Seeking out an affair

✓ Lashing out or being very short-tempered

✓ Perfectionism

✓ Inability to concentrate

✓ Extreme guilt

✓ Self-medicating with alcohol, cigarettes, food, or other addictions