I began to, but soon desisted. I became disillusioned with the studies: in the way they were conducted, and in the conclusions they came to. Invariably, the studies didn’t take into account possible confounding variables (factors that would skew the study) or they would confuse correlation with causation.
If I didn’t trust the studies, I couldn’t use them.
Besides, studies often find what we already intuitively ‘know’, and then make trite recommendations. For example, I don’t believe that my readers need a study to tell them that ‘positive thinkers are, in general, happier than negative thinkers’. They have already figured that out for themselves. And, they don’t need to be told tritely, ‘Therefore, become a positive thinker and you will be happier.’ If only it were that simple!
I want a deeper approach, and studies get in the way.
Further, when I first began writing the book, and referred to studies, I soon realised that I was using studies to support my point of view. I was aiming to persuade the reader that what I said was right. That troubled me. I want my readers to decide for themselves if my views have merit; I don’t want them feeling obliged to adopt my point of view because I have a study to back me up.
Anyway, it would be easy for me to use studies which support my point of view, and ignore the studies which don’t. (That’s not uncommon in the world of authors.) The best way to avoid that is to not use studies at all.
If I don’t include studies the reader can only assume that what I say is my opinion. That’s healthy. The reader can take what they want from my book and comfortably ignore the rest.