“If you understand the linkages between your past experiences and current emotions, your stress will begin to lift,” Peterson said. He pointed to the work of James Pennebaker, a professor at the University of Texas at Austin, who had found that students who wrote about the worst thing that had ever happened to them felt sadder initially, but six months down the road were visiting doctors less frequently. Dozens of subsequent studies by Pennebaker and others showed similar benefits to physical and psychological well-being. Asking people to document difficult emotional experiences was shown to improve immune function, lower heart rate, and ease blood pressure. (p. 140)
Kamenetz, A. (2013). Power of the Pen. Oprah Magazine, 14 (12), 140-143.