From the 'Happiness Hypothesis'
by Jonathan Haidt

"Pennbaker discovered that it's not about steam; it's about sense making. The people in his studies who used their writing time to vent got no benefit. The people who showed deep insight into the causes and consequences of the event on their first day of writing got no benefit either: They had already made sense of things. It was the ones whose health improved over the next year. In later studies, Pennbaker asked people to dance or sing to express their emotions, but these emotionally expressive activities gave no health benefit. You have to use words, and the words have to help you create a meaningful story. If you can write such a story you can reap the benefits of reappraisal (one of two healthy coping styles) even years after the event. You can close a chapter of your life that was still open, still affecting your thoughts and preventing you from moving on with the larger narrative."
p. 148