Lion's mane is a fungus that has a very noticeable effect on the brain.
Strangely, it's Wikipedia page is only a short paragraph.
Note on that page the reference to gibberellin in cultivation. That hormone used to be marketed to curious people as a way to induce mutations.
Healthline is a mainstream medical information website, one of the top 150 sites in the United States, with more than 200 employees.
Among the possible health benefits listed for Lion's mane on Healthline are
1) May protect against dementia,
2) May speed recovery of nervous system injuries,
3) Helps manage diabetes symptoms,
4) May help with cancer,
along with several other possible benefits.
The industrialized melting pot views illnesses and medicines in a way that is conducive to creating
b) profit and
The goal of the melting pot is uniformity, a common view of everything. Effectiveness of a medicine is important, but secondary to its large scale acceptance and use. Melting pot medicine starts with 'experts' and other infrastructure and includes patients as consumers.
Traditional medical systems are based on practicality and involve one primary person, the individual, but usually also include an 'expert' in the abstract medical history of that tribe, somebody like a Shaman or elders who an individual consults.
Very often a medicinal plant will 'treat' a disease that involves what melting pot medicine considers several unrelated systems. For example Lion's mane is used for brain function, diabetes, cancer and other things. This suggests that the 'worldview' or paradigm used in melting pot medicine is flawed.
Traditional medical systems, developed in isolated homogenous tribal societies, have developed numerous paradigms around their medicines.
When a traditional society is 'consumed' by a melting pot, there may be polite recognition of the tribal paradigm but It generally becomes invisible within a few generations.
Despite having some extremely unusual, useful effects, which can easily be observed, minimal scientific research has been done on Lion's mane. Most of the people who would benefit from it are not told about it when they visit a melting pot doctor, though some doctors do pay polite respect to medicinal plants simply because they often work.
No money is spent pushing doctors to give patients plants, but vast sums of money are spent pushing them to prescribe synthetic chemicals.
Here is a website that provides a modest bit of research involving lion's mane.
Note that WebMD has only a brief skeptical page on a Lion's mane, with only two reviews.
Here are some scientific articles.
One of the interesting things about Lion's Mane is that it's effect seems to vary according to when in the day it is taken.
With only the little bit of research that has been done, it is safe to say that Lion's mane would be more effective than many expensive prescription medicines for a number of illnesses, and there is enough evidence to justify using it for many 'untreatable' illnesses i.e., illnesses that the pharmaceutical companies have not found a chemical for yet to manage symptoms.