The study definitely uses tricky wording, but it doesn't seem very safe to me to chronically lower serotonin via pharmaceuticals to combat Alzheimer's/depression. The serotonin transporter goes down due to insufficient levels of salt in the diet, so I think eating more salt is the best way to keep serotonin low, rather than using pharmaceuticals, because in addition to lowering serotonin, salt also lowers histamine (because it raises CO2 production). The problem with pharmaceuticals is that by lowering serotonin without necessarily raising CO2 production, they might have the side effect of raising histamine.
I think serotonin might go up as a protective reaction against excess histamine, as dulling the emotions via serotonin is the body's back-up way of protecting against the emotional instability caused by histamine when the body doesn't have enough energy to produce CO2, which is the healthy way to keep histamine low.
It seems the real cause of Alzheimer's and depression might be excess histamine, not excess serotonin. But lowering histamine is hard, aside from milk, thyroid, vitamin D, coffee, chocolate, niacinamide, salt, and cold showers, I don't really know what else works.
Dual H3R antagonist/5HT4R agonist (such as Ozone) have potential for the treatment of neurodegenerative diseases such as Alzheimer's disease.
Dual histamine H3R/serotonin 5-HT4R ligands with antiamnesic properties: pharmacophore-based virtual screening and polypharmacology - PubMed
In recent years, preclinical and clinical studies have generated considerable interest in the development of histamine H3 receptor (H3R) antagonists as novel treatment for degenerative disorders associated with impaired cholinergic function. To identify novel scaffolds for H3R antagonism, a...
pubmed.ncbi.nlm.nih.gov