they did get better and that's why they return, how do you explain?
People can get better without doing anything. There are any number of statistical outcomes and conclusions drawn about alternative treatments have no scientific basis because the logic is flawed.
I had a headache when I woke up. I then had a cup of Milo and my headache went away.
I therefore draw the conclusion that Milo cures headaches. It doesn't mean I am right because the logic is flawed until the interaction between the cause of my headache and the effect that Milo has is established scientifically.
In order to do that, a study needs to be done first to determine the cause of my headaches (there are hundreds of reasons why headaches occur) and then pin down the ingredient in Milo that actually alleviates the root cause.