I’m sure they are. After all, the market for antidepressant drugs is over $15B[1] , so there is a lot of money to be made here.
But it won’t be easy. And if you think about the process of drug discovery, you’ll see why. Some drugs are indeed discovered fortuitously. The discovery of penicillin is often held out as an example – Fleming’s contaminated petri dish leading to the production of a wonder drug.
But drug discovery nearly always requires a theory of the mechanism of disease causation. You can’t just pump random chemicals into humans (or even mice), hoping to find one that has the desired therapeutic effect. It would take too long, cost too much and be too likely to fail completely. A theory of disease allows you to focus your efforts, and to develop model systems that can identify plausible drug candidates.
This is true even for the supposedly fortuitous discoveries. Sure, Fleming got lucky when his petri dish of Staph aureus was contaminated by Penicillium mold (a frequent occurrence, as any microbiologist can tell you). But he only had a petri dish of Staph because of the germ theory of disease – he already knew that a specific bacterium was responsible for causing deadly infections. He used this theory to create a drug discovery paradigm: find a compound that kills Staph, but is not toxic to humans. He was prepared to be lucky.
We don’t yet have a paradigm for exploiting the microbiome as a drug target. We don’t really understand how the microbiome influences mood. We don’t understand what constitutes a healthy microbiome, and how its composition differs between people, and how it changes in response to environmental factors. Without a clearer understanding of these concepts it is hard to build model systems to test drug candidates.
We are probably at about the same stage in microbiome research as cancer research was in the early 1980s when oncogenes were being discovered and described. We knew they were important for cancer, but couldn’t tell which ones were drivers of disease and should be the focus of discovery research. It’s only in the last decade that oncogene science has gotten translated into a steady pipeline of targeted cancer therapeutics.
These problems are all solvable – they are not mysteries. But it could well take a decade before clinical solutions arrive. In the meantime, we could see a better understanding of how other agents – including antibiotics[2] and existing anti-depressant drugs[3] – interact with the microbiome to affect mood.
Footnotes
[1] Global Depression Drug Market Poised to Surge from USD 14.51 Billion in 2014 to USD 16.80 Billion by 2020
[2] Antibiotic exposure and the risk for depression, anxiety, or psychosis: a nested case-control study.
[3] Antidepressants, antimicrobials or both? Gut microbiota dysbiosis in depression and possible implications of the antimicrobial effects of antidepre… – PubMed – NCBI