[savingthrow]

> But in her late 20s Jacka managed to recover and stay well by focusing on her diet, exercise and sleep.

Depression is a relapsing and remitting illness so people get better and worse all the time as a normal part of the illness.

Depression is a word that covers a wide range of different forms of illness.

We have no idea if better sleep, exercise, and better food played any part in her recovery. We don't know if that is applicable to other people. We don't know how to tell who will experience recovery from depression from exercise (good evidence that it's not many people) or better food (not much evidence either way) ro sleep (good evidence that it's important).

With almost all of these we find that there's not much attempt to work out the causal direction. (Is Joe Soap depressed because he eats junk food, or does he eat junk food because he's depresed and can't shop or cook?).

Unsurprisingly, this person is selling a book, which is usually a sign of an oversold bit of research.