challenging gut bacteria for mindful, hormonal changes

The following is an extract from GUT by Guilia Enders 2015, published by Scribe, Pp.129-130
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Patients with intestinal disease who also suffer from extreme anxiety or depressive disorders are often recommended anti-depressants by their doctor. However, they are rarely told why, and there is a simple reason for that: No doctor or scientists knows. It was not until they noticed the mood-enhancing effects of these drugs that scientist began to explore the mechanisms behind this phenomenon. They still have to come up with a clear answer. For decades, it was thought to be due to an enhancing effect on the 'happiness hormone' Serotonin. More recently, depression researchers have also begun investigating another possibility - that such drugs may increase the plasticity of the nerves. 

Neuroplasticity is the nerves ability to change. 
It is nerve plasticity that makes puberty such a confusing time for an adolescent brain - so  much is still being moulded into shape.  The possibilities are endless, and nerves are constantly firing off messages in all directions in a pubescent brain.  This process is not complete until we reach the age of about 25.  

95% of Serotonin we produce
is manufactured in our gut

After that, nerves react according to well-rehearsed patterns.  Patterns that have proved useful in the past are retained; others are rejected as failures. This explains the disappearance not only of the inexplicable fits of laughter and temper tantrums of our teenage years, but also the posters on our bedroom walls. After this age, we find it more difficult to deal with sudden change, but the payback is a more table, calmer disposition. This can also result in negative thought patterns taking root, such as 'I am worthless' or 'Everything I do goes wrong'. The nervous messages from a worried gut can also become embedded in a person's mind. If it is the case that anti-depressants increase neuroplasticity, they may work by loosening up such negative thought patterns. This is most beneficial when accompanied by effective psychotherapy to help patients resist slipping back into old habits. 

The side effects of commercially available anti-depressants, such as Prozac, also provide us with important clues about the 'happiness hormone, Serotonin. A quarter of the patients will report typical side effects such as nausea, an initial phase of diarrhoea and constipation when the drug is taken over a long period of time. This is explained by the fact that our gut brain possesses the same neural receptors as the brain in our head. So, anti-depressants automatically 'treat' both brains. 

The American researcher Dr Michael Gershon, takes this line of thought one stage further. He is interested in the possibility of developing effective anti-depressants that only influence the gut and do not have an effect on the brain.
Dr. Gershon's research is not as outlandish as it might first seem. After all, 95% of the Serotonin we produce is manufactured in the cells of our gut, where it has an enormous effect on enabling the nerves to stimulate muscle movement, and acts as an important signalling molecule. If its effects on the gut can be changed, the messages sent from there to the brain would also be changed enormously. This would be particularly useful in treating the sudden onset of severe depression in people whose lives are otherwise fine. Perhaps their gut needs a session on the therapists couch, and their head is not to blame after all.