The most common way to use a brainwave entrainment is for a short-term benefit, to help guide your brain into a particular mental state at the time you need it. In a similar way to how you might take a sleeping pill before bed to help you get to sleep, or maybe drink some coffee or an energy drink to help wake you up and give you a boost of energy.
Anabel caught this Raikou after it was released following the battle against the Masked Man. She is said to have captured this Legendary Pokémon during her trip somewhere in Johto. Raikou has been with her since then and she continues to rely on it for all of her battles. Because it carries a large thundercloud on its back, it both allows a handier usage of its trademark Thunder as well as strengthen it.
As bizarre as it may sound, the bacteria in your gut might be contributing to stress. Research has shown that the brain signals to the gut, which is why stress can inflame gastrointestinal symptoms; communication may flow the other way too, from gut to brain. A 2013 UCLA study among 36 healthy women revealed that consuming probiotics in yogurt reduced brain activity in areas that handle emotion, including stress compared to people who consumed yogurt without probiotics or no yogurt at all. This study was small so more research is needed to confirm the results—but considering yogurt is full of calcium and protein in addition to probiotics, you really can't go wrong by adding more of it to your diet.