Anhedonia is the inability to experience pleasure, even with activities that previously brought you joy or satisfaction. Perhaps you enjoy gardening, anticipating springtime with excitement when you can plant bulbs and annuals, watching them bloom beautiful flowers in a few weeks. Or you enjoy working in your woodshop, creating decorative pieces or furniture.
But then you find yourself losing interest in your favorite pastimes and other activities. The thought of springtime flowers or a beautiful rocking chair no longer excite you. You also lose interest in the little pleasures in life such as a nice meal at a restaurant, the company of friends, or a new movie. Part of anhedonia can also be withdrawal from social activities. Many of us have experienced something akin to this at least somewhere along the way over a lifetime.
Anhedonia is a major feature of depression, though can also occur in conditions such as Parkinson’s disease, dementia, and schizophrenia. It can be accompanied by feelings of sadness or it can occur in isolation. Loss of interest in sex is also regarded as a major feature of anhedonia. There is evidence suggesting that anhedonia increases the likelihood of developing dementia and puts the sufferer at greater risk for suicide.
You are familiar with the conventional “solutions” for anhedonia: selective serotonin-reuptake inhibitors (SSRIs) and other antidepressants, drugs specific for a condition such as Parkinsonism, and counseling. We all recognize that conventional solutions have severe limitations, not to mention side-effects and costs.
It’s also becoming clear that gastrointestinal (GI) microbes play important roles in influencing mood, emotions, our internal dialogues, and potential for anhedonia. Among the possible ways that the “gut-brain” axis can exert these effects are:
- Loss of key species that control intestinal production of serotonin—Turicibacter sanguinis is a recent microbial connection that appears to play an outsized role in determining how much serotonin is produced by the GI tract. (Not yet available commercially.)
- Loss of key species that produce oxytocin—Our friend, Lactobacillus reuteri, lost by nearly all modern people is, of course, a major player here. A reduction in the capacity to produce oxytocin increases potential for social isolation, suicide, divorce, and anhedonia.
- Loss of key species that produce butyrate—Intestinal butyrate is a major mediator of numerous brain functions. Loss or reduced populations of species such as Faecalibacterium prausnitzii, some Clostridia species, and species of Ruminococcaceae and Lachnospiraceae, all major butyrate producers, can not only add to anhedonia, but also negatively influence the content of your internal dialogue and disrupt sleep.
- Overgrowth of Proteobacteria that cause endotoxemia—This is a major factor in mood and emotions. Loss of butyrate-producing species, loss of small intestinal and colonic microbes that produce bacteriocins (natural antibiotics effective against Protobacteria), and intestinal wall inflammation lead to overgrowth of species such as E. coli, Klebsiella, and Campylobacter that, upon their death, release the endotoxin component of their cell walls that then can gain entry into the bloodstream: “endotoxemia.” Human clinical studies in which very small amounts of endotoxin were injected into non-depressed humans caused depressive symptoms within a few hours, accompanied by the hallmarks of depression by brain MRI, strongly suggesting that endotoxemia is a major driver of depression and anhedonia.
- Loss of GI species diversity—Because modern people have lost hundreds of microbial species in their bowel flora, we have experienced a dramatic reduction in the diversity of species we carry. Compared to hunter-gatherer populations unexposed to antibiotics and other factors, for instance, we have far less diversity. Increased excretion of the endocannabinoid, palmitoylethanolamide (PEA, that some label “endogenous cannabidiol,” CBD, because PEA and CBD overlap in effect), in stool may be one way in which reduced species diversity leads to anhedonia. This can explain why oral supplementation of PEA has been associated with an antidepressive effect.
I hope that you are coming to appreciate that viewing depression and anhedonia as manifestations of disrupted brain chemistry are wild oversimplifications, but one that serves the pharmaceutical industry well. I hope that you have also come to appreciate the enormous role that gut microbes play in determining so much of what goes on inside your brain. We don’t yet have specific targeted solutions to correcting the full array of microbiome factors that contribute to these situations. But consider these solutions that are currently available and have potential to introduce major improvements in mood and emotions, including relief from anhedonia:
- Frequent consumption of fermented foods—Even though foods such as kimchi, kombucha, fermented meats, yogurts, kefirs, veggies you ferment on your kitchen counter, etc. yield species such as Pediococcus pentosaceus and Leuconostoc mesenteroides that do not take up residence in your GI tract, their presence, although transient, somehow (not clear how) encourage a return of species diversity. One exception: some strains of Lactobacillus plantarum from fermented foods may take up residence and contribute to reduced anhedonia.
- Restore L. reuteri-–This, of course, we have discussed at great length and are witnessing some pretty spectacular effects, emotional and physical, due to oxytocin and to this species ability to colonize the GI tract and produce bacteriocins that reduce Proteobacteria numbers and thereby endotoxemia.
- Address small intestinal bacterial overgrowth (SIBO)—By my estimation, 50% of the population has this overgrowth of mostly Proteobacteria in the 24-feet of small intestine and causing endotoxemia with effects on the brain. By the way, we are achieving this, with results far beyond my expectations, by restoring small bowel-colonizing and bacteriocin-producing species in my recipe for SIBO Yogurt.
- Include prebiotic fibers, especially sources of inulin and oligofructose (e.g., onions, garlic, shallots, unripe green banana, commercial powders), that increase populations of butyrate-producing species while also providing the substrate required for butyrate production.
If you have struggled with anhedonia and/or depression and your doctor has not mentioned any of the above to you, he/she has done you a disservice, handing you a prescription for a SSRI or other agent of severely limited potential benefit. We are entering the age of psychobiotics in which informed management of bowel flora issues gives us enormous control over our mental health, whether or not doctors are involved.
