Could lemon balm help people with dementia?

Rosmarinic acid (RA), which is found in lemon balm, has showed promise for Alzheimer’s disease (AD) in lab and animal studies, preventing amyloid β-protein from forming the fibrils that lead to the plaques and tangles characteristic of AD,^[1] but there isn’t much evidence that this will translate to people. An early randomized controlled trial (RCT) of hydroalcoholic lemon balm extract in 42 adults in Iran with mild to moderate AD found cognitive improvements over four months,^[2] although there was some risk of randomization and reporting bias in that trial. But more recent research hasn’t borne this out. A small 2020 RCT of lemon balm extract (providing 500 mg/day of RA) in 23 adults in Japan with mild dementia likely caused by AD found that, while lemon balm was safe and effective, there were no cognitive differences between the lemon balm and the placebo groups; the only significant difference was a reduction in the “irritation/lability” subscale on one test, which is in line with what we know about lemon balm’s calming effect.^[1] A follow-up RCT by the same researchers, of the same extract in the same dosage, in 323 adults without dementia but with subjective or mild cognitive impairment, failed to find any significant effect on cognition except in post-hoc subgroup analysis.^[3]

Lemon balm extract has also been studied for memory in young people without dementia, without conclusive results. Some lemon balm extracts have shown acetylcholine receptor activity in the lab, which is of potential interest both for cognition and for treatment of the cholinergic dysfunction seen in Alzheimer’s disease.^[4][5][6] A pair of pilot studies in the early 2000s tested the effects of lemon balm extract on a broad battery of cognition tests in young adults, with the second study focusing on an extract that showed cholinergic activity in the lab; the largest effect was a reduction in the speed of memory tasks after taking lemon balm (i.e., participants were slower to complete timed tasks), with a small improvement in accuracy for some doses and timepoints.^[4][5] Because of the large number of outcomes, the small number of participants, and the study design, these results are preliminary. Further, focused research would be needed to verify any positive effect of lemon balm extract on memory.

Although there’s not much evidence that lemon balm can help with memory, it might help with agitation in people with dementia when taken orally. A 2003 RCT of lemon balm extract for cognition in people with AD that recorded side effects noticed that the participants who were taking lemon balm experienced less agitation, although this wasn’t one of the study’s outcomes.^[2] And, as mentioned above, the 2020 Japanese RCT of lemon balm in people with AD noticed a reduction in irritation and lability.

Aromatherapy with lemon balm oil, diluted and applied to the skin, has also been evaluated for agitation in people with dementia, but the evidence so far is equivocal: One 2002 trial found that people with dementia who received lemon balm aromatherapy showed less agitation than those who received sunflower oil,^[7] but a similar 2011 trial found that there was no significant difference between lemon balm and sunflower oil.^[8]