Tickling and Stress
I've never seen any studies on this, although, this is one of those subjects that seems almost a common sense to me. I have only a few examples in my own life. For the last couple of months we have been going through a period of stress in our lives as serious as we have experienced since we were married. It built and built until it hit its peak just a week or so ago.
A few days before that I was sitting on the edge of my bed watching some goofy thing on TV. It was about 11:00 AM. My wife came and sat next to me on the bed. She fell over backwards and stretched her arms over her head. On a whim I put a hand up under her shirt and tickled her belly button for just a second or two. She giggled and flinched but did nothing to tell me to stop.
I stood up and picked her feet up and put them againdst my chest. She made her legs rigid, and I pushed her higher on the bed. She actually giggled a little more. I went up on the bed and pulled her shirt over her head but not completely off, so it was inside out and her arms were still inside it. This let me kneel on the shirt so as to lock her arms in position. I think she sensed the need for this because she never resisted any of this for a second. The tickling was then long and deliberate and merciless.
I'm here to tell you that she spent the next 4 or 5 hours with a look of complete relaxation and contentment. There was no stress in this house for that period. This was a case when tickling relieved stress very much better that ANYTHING else we could possibly have done. Since it was one of those rare times when she fought against it not at all before hand, in fact she invited it without saying so; there is no doubt it was something she both wanted and realized she needed.
So did I. I'd recommend this as a stress relief far better than any pill you can take.