Methylene Blue and Memory: What the Human Studies Actually Found

In 2016 a group in Texas published, in Radiology, a randomized, placebo-controlled study of a single oral administration of methylene blue in twenty-six healthy adults, who then performed memory and attention tasks inside an MRI scanner. The methylene blue group showed increased activity in brain regions involved in attention and short-term memory, and — the headline — a modest improvement in memory retrieval on the task compared with placebo.

It is a well-designed, well-conducted study and it deserves its citation. It is also one study, in twenty-six people, of one administration, measuring a task in a scanner an hour later. It does not tell us whether the effect persists, accumulates, or matters outside a laboratory; it has not been replicated at scale; and it was designed to demonstrate a mechanism, which it did, rather than a treatment, which it was not. Every "methylene blue improves memory by 7%" claim traces to it, and the number is doing more work in marketing than its authors asked of it.

The other human cognition-adjacent evidence comes from psychiatry. A Canadian group ran a crossover trial in which people with bipolar disorder on mood stabilizers received methylene blue at two different strengths for several months each, and found that the higher strength was associated with lower depression and anxiety scores. Earlier, smaller studies from the 1980s reported similar findings.

These are studies of mood in a psychiatric population, not of memory in healthy adults, and their relevance to cognition is indirect: the same mitochondrial mechanism is proposed, and depression itself impairs thinking. They are also small. They are cited here because they are among the only controlled human trials of methylene blue over months rather than hours, and because they show it was tolerated over that period — which is a safety point, not a cognitive one.

The largest human investment in methylene blue and the brain has been the effort to turn it into a treatment for Alzheimer's disease. Methylene blue inhibits the aggregation of tau, the protein that forms tangles in Alzheimer's, and a company developed a stabilized, reduced form of the molecule — first as Rember, then as LMTM or hydromethylthionine, trial name TRx0237 — and took it through a decade of trials in thousands of patients.

The results are, at best, contested. The two large phase 3 trials published in 2016 failed their primary endpoints: LMTM added to standard treatment was no better than the comparator on cognition or function. The company's subsequent analyzes argued that a benefit appeared in patients taking it alone rather than alongside other drugs, and a further trial designed around that hypothesis reported in 2023 with results the company described as positive and much of the field described as inconclusive, because the comparison relied on a low-strength control arm and historical data rather than a true placebo.

Whatever one makes of that debate, it is a debate about a different molecule, in a different form, in people with a neurodegenerative disease, at strengths chosen for tau inhibition. It is not evidence that methylene blue improves memory in a healthy fifty-year-old, and it is regularly cited as if it were.

Add it up. A mechanism that is sound. Animal data that are consistent. One single-administration human imaging study with a modest task effect. Mood trials in a psychiatric population. An Alzheimer's program in a modified molecule that has not convinced regulators. No trial — none — of methylene blue taken over weeks or months for cognition in healthy adults, and therefore no evidence that the fMRI effect persists, accumulates, or translates into a difference a person would notice.

That is not nothing. It is enough to make methylene blue a plausible, low-cost thing to try, with expectations set accordingly and safety rules observed absolutely. It is not enough to call it a cognitive enhancer, and we do not. The main page says what we prescribe it for and how honestly we frame it; the brain fog a person hopes it will fix is usually something the workup finds first.