What is behind Low Mood & Depression
Serotonin — the neurotransmitter of mood and satiety, and the precursor the body converts to melatonin for sleep. Evidence A — Human trial evidence.
The chemistry of wanting, not of liking. Dopamine sets how much effort a goal feels worth — which is why its loss reads as apathy long before it reads as sadness. More is not better: the same system that drives pursuit drives compulsion. Evidence A — Human trial evidence.
Insulin-like growth factor-1 — the dermal-papilla growth factor that drives follicle proliferation and prolongs anagen (the active growth phase). Evidence A — Human trial evidence.
The master inflammatory switch — indispensable to defend against threat, corrosive when it never stands down. Evidence B — Preclinical.
The hypothalamic–pituitary–adrenal axis and its hormone cortisol — the body's central stress-and-recovery command. Evidence A — Human trial evidence.
Mitochondrial energy (ATP) output. Evidence A — Human trial evidence.
The alternative fate of tryptophan — away from serotonin and toward NAD+ and neuroactive metabolites. Also carries the IDO enzyme step, which is what inflammation induces. Evidence A — Human trial evidence.
A sensor of cellular stress that ignites inflammation driven by damage rather than by germs. Evidence A — Human trial evidence.
The intestinal barrier — the selective wall that admits nutrients, excludes toxins and anchors the gut–brain and immune dialogue. Evidence A — Human trial evidence.
Not happiness — stability, and the whole positive dimension of how life feels. The finding that changes how to read this pathway: feeling good is not simply the absence of feeling bad. When researchers statistically removed depression and anxiety from the analysis, the health benefits of positive wellbeing were still there — they are independent dimensions, not two ends of one line. That is why mood runs outward to sleep, inflammation, glucose, wound healing, infection resistance and survival itself, and not only inward from them. Evidence A — Human trial evidence.
Evidence on these pathways
Dopamine → Melatonin. “Through α1B-D4 and β1-D4 receptor heteromers dopamine inhibits adrenergic receptor signaling and blocks the synthesis of melatonin induced by adrenergic receptor ligands.” — Circadian-Related Heteromerization of Adrenergic and Dopamine D4 Receptors Modulates Melatonin Synthesis and Release in the Pineal Gland. PLoS Biology, 2012, volume 10, e1001347. doi:10.1371/journal.pbio.1001347
Dopamine → Mood (Positive Affect). “Boosting dopamine also increased happiness resulting from some rewards.” — Dopaminergic Modulation of Decision Making and Subjective Well-Being. Journal of Neuroscience, 2015, 35(27), 9811-9822. doi:10.1523/JNEUROSCI.0702-15.2015 | PMC4495239
Intestinal Barrier → Ammonia. “This weakens the paracellular seal of the intestinal epithelium, enabling microbial products such as endotoxins, ammonia, and even whole microorganisms to translocate into the portal circulation.” — How the gut-liver axis shapes hepatic encephalopathy: mechanistic and therapeutic perspectives. Exploration of Digestive Diseases 2025;4:100597. doi:10.37349/edd.2025.100597 (no PMID exists — the journal is not MEDLINE-indexed; absence confirmed on file, not derived)
Intestinal Barrier → Oxygen-Carrying Capacity. “The two main causes are the villous atrophy of the mucosa at the site of iron absorption (the duodenum) and the resulting inflammation, which triggers the mechanism that leads to the anemia of chronic disease.” — Persistent Iron Deficiency Anemia in Patients with Celiac Disease Despite a Gluten-Free Diet. Nutrients, 2020, 12(8), 2176. doi:10.3390/nu12082176
Formulas that act on these pathways
Acts on 6 of these pathways: Serotonin, Dopamine, NF-κB, HPA Axis / Cortisol, Kynurenine Pathway, Mood (Positive Affect).
Acts on 6 of these pathways: Serotonin, Dopamine, NF-κB, HPA Axis / Cortisol, Intestinal Barrier, Mood (Positive Affect).
Acts on 5 of these pathways: Serotonin, Dopamine, NF-κB, HPA Axis / Cortisol, Intestinal Barrier.
Acts on 4 of these pathways: Serotonin, Dopamine, HPA Axis / Cortisol, Mood (Positive Affect).
Acts on 4 of these pathways: Serotonin, NF-κB, HPA Axis / Cortisol, Intestinal Barrier.
Acts on 4 of these pathways: Serotonin, Dopamine, HPA Axis / Cortisol, Mood (Positive Affect).
What this page does not claim
This page names the pathways involved and the published evidence on each. It does not claim that any formula treats, cures or prevents Low Mood & Depression. A pathway opens here only on graded, published evidence, under a standard fixed before the evidence was gathered, and every figure above carries its grade.
These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.