The joy of writing: scientists measure how writing expressively can calm the mind. From the article:

One important type of brain wave is a sharp negative (downward) signal that occurs when you make an error, even if you are not aware of it. And in people who worry, this negative signal is much larger. The larger signal reflects the compensatory effort that anxious people need to make when tuning out distracting worries. This extra effort uses thinking resources that could otherwise be better used to focus on other activities, for example answering test questions.

If expressive writing frees up mental resources, we would expect the negative signal to be reduced, as there would be fewer distracting worries stored in the brain.

[Hans S.] Schroder and his colleagues conducted an experiment on 44 female students from a midwestern university….

One group of participants was asked to engage in expressive writing about their worries, while the comparison group was asked to engage in writing unrelated to their worries. Then they were also given a computer task designed to elicit the negative-signal brainwaves.

Compared to writing about things other than one’s worries, expressive writing about one’s worries did in fact reduce the size of the negative brain wave signal in people who worried a lot. This implied that “offloading” your worries into free-form writing frees up mental resources that you can then use to complete tasks more easily.