It's often not what you think
Many of the therapies in this book are what are known as complementary or alternative therapies, and sometimes there is little or no scientific research to prove whether or not they are effective.
In cases like these, the term often used is "no scientific evidence had been found" to determine their efficacy. However, the reader should know that, in many cases, the term "no scientific evidence has been found" also means "no scientific evidence has been looked for".
This is because it is a very expensive and time consuming process for a therapy or treatment to be put through and pass the battery of tests required by the various medical authorities before they will endorse it, which is why funding for these tests is usually derived from the pharmaceutical industry.
No vested interest
But there is no vested interest for the pharmaceutical industry to fund an array of tests into complementary and alternative therapies when they are unlikely to profit from the results. In other words, the research and testing into most alternative or complementary therapies will probably not lead to the development of a new and profitable drug. And in fact, if the therapy is found to be effective, it may even lead people away from taking prescribed medicines.
If people have been using a therapy for thousands of years, there's a good chance that it has something to recommend it. Many such therapies are derived from the East and thus built on a completely different system of science which is not recognised by modern Western science.
So please bear all of the above in mind when reading the term "no evidence has been found" throughout this book, and use your common sense. And the same goes for the term 'pseudoscience', which is often said of something that has not been proven by modern Western science. It does not necessarily mean that its proponents have tried to find scientific evidence for its efficacy and failed.