Is you gut bacteria giving you depression?

Your body is loaded with trillions of bacteria. Paired with other tiny organisms like viruses and fungi, they make what’s known as the microbiota, or the microbiome. The mix of bacteria in your body is unique to you. It’s determined partly by your mother’s microbiota and partly by your diet and lifestyle. Between 300 to 500 different kinds containing nearly 2 million genes live in your gut. They line your entire digestive system, but most live in your intestines and colon. They help process food and affect everything from your metabolism to your mood to your immune system. They may be tied to your risk of diabetes, obesity, depression, and colon cancer.
Researchers have found that among over 2,100 adults, those with depression showed differences in specific groups of gut bacteria. Those microbes are believed to do much more than aid in digestion. Research suggests they are involved in everything from immune system defenses to producing vitamins, anti-inflammatory compounds and even chemicals that influence the brain. People with higher concentrations of certain other gut bugs generally reported better mental well-being. Most research on such "gut-brain" communication has been done in animals. Jeroen Raes, a researcher who spearheaded this project, looked for links between gut microbes and depression among over 2,100 adults taking part in two health studies. The investigators found that levels of two specific groups of gut bacteria Coprococcus and Dialister were "consistently depleted" in people with depression. Meanwhile, people with higher levels of Coprococcus, and another group of bacteria called Faecalibacterium, typically showed better ratings to their quality of life. Both types of bacteria break down fiber to produce an anti-inflammatory compound called butyrate.
However, this doesn’t prove that gut microbes aid in depression. This is like the chicken and egg scenario. People diagnosed with depression have different eating routines, food habits and different habits. This in turn could cause the growth of certain gut bacteria. This gut bacteria in turn feeds into these habits associated with depression, which reinforces it. 
Studies in recent years, largely in animals, have been uncovering links between the composition of the gut microbiome and the risks of various health conditions -- from other brain-related disorders, like obesity, auto-immune diseases and even dementia. But the degree to which gut bacteria contribute to any human diseases remains unclear. Hence the nature of the relationship was declared correlational not causational. Even if the gut microbiome does influence depression symptoms, anything as simple as a probiotic supplement would not offer a quick fix. Depression is a complex disorder that has several influential factors that have not been considered.