Yep, exercise is a key factor. In the context of this article, by 'serious' insomnia, I meant cases that are not just psychological (eg stress). I didn't mean

Yep, exercise is a key factor. In the context of this article, by 'serious' insomnia, I meant cases that are not just psychological (eg stress). I didn't mean to downplay significant sleep troubles due to stress alone. Even in those cases, non-psychological factors should be considered.