Content words label an object or action. They include Nouns, Verbs, Adjectives, and Adverbs.

Function words connect, shape, and organize content words. They include Pronouns, Articles, Prepositions, Auxiliary verbs, Negations, Conjunctions, Quantifiers, and Common Adverbs.

Function words do not themselves carry much meaning, and are generally not noticed. However, they are used at a very high rate, and can tell us things about their user that content words can not.

Content words and function words are implemented differently by the brain:

Does writing style come from function words?

These Twitter streams have been analysed to find the proportion of different word types. In the key, FPS = First Person Singular Pronouns ("me"); FPP = First Person Plural Pronouns ("we"); SP = Second Person Pronouns ("you"); TP=Third Person Pronouns ("they").

As an example, higher use of First Person Singular Pronouns has been associated with depression; lower use of First Person Singular Pronouns has been associated with self-confidence, and positions of power. Average use of "I" is 3.64%.

Many studies have found psychological and physical health benefits in writing.

The writing of people who experienced health benefits tended to have:

Writing and health research summaries

The Healing Powers of Expressive Writing

Janel D. Sexton and James W. Pennebaker, The Psychology of Creative Writing, 2009, ISBN-13 978-0-511-59538-7

Writing patterns that predict improved health

i.e. the person whose health benefits from their writing is expressing a high rate of positive emotion, but also acknowledging the negative, and is endeavouring to make meaning of events.

Writing patterns suggestive of worse health

The Secret Life of Pronouns: Flexibility in Writing Style and Physical Health

R. Sherlock Campbell and James W. Pennebaker, The University of Texas at Austin, January 2003

Numerous disclosure studies have demonstrated that individuals randomly assigned to write about emotional topics evidence improved physical health compared with those who write about superficial topics.

In these studies, individuals are randomly assigned to write about either emotional or nonemotional topics for 15 to 20 min per day for 3 to 5 consecutive days. In the past 15 years, dozens of replications have demonstrated that emotional writing can influence frequency of physician visits, immune function, stress hormones, blood pressure, and a host of social, academic, and cognitive variables. These effects hold up across cultures, ages, and diverse samples (Pennebaker & Graybeal, 2001; Smyth, 1998)

Flexibility in the use of common words - particularly personal pronouns - when writing about traumatic memories was related to positive health outcomes.

The analyses suggest the potential role of pronouns as markers of psychological and physical health, and, indirectly, of people's thinking about their social worlds over the course of their writing.

Cognitive Words and Inflammatory Responses

American Psychological Association, Health Psychology, 2009, Vol. 28. No. 5, 621-630

In accord with research demonstrating the value of cognitive processing in emotional disclosure, this research suggests that productive communication patterns may help mitigate the adverse effects of relationship conflict on cell inflamation.

Cognitive word use between spouses was associated with healing of cell inflamation following conflict, but not non-conflict, discussions.

Stepping back to move forward: Expressive writing promotes self-distancing

Park, Jiyoung; Ayduk, Özlem; & Kross, Ethan. Emotion, Vol 16(3), Apr 2016, 349-364

Prior research indicates that expressive writing enhances well-being by leading people to construct meaningful narratives that explain distressing life experiences. But how does expressive writing facilitate meaning-making? We addressed this issue in 2 longitudinal studies by examining whether and how expressive writing promotes self-distancing, a process that facilitates meaning-making. At baseline in both studies, participants reflected on a distressing life experience. In Study 1 participants were then randomly assigned to write about their distressing experience or a non-emotional topic for 15 min on 3 consecutive days; in Study 2 participants were randomly assigned to write or think about their distressing experience or write about a non-emotional topic for the same amount of time. One day following the intervention, expressive writing participants in both studies self-distanced more when they reflected over their distressing experience compared with participants in the other conditions, which in turn led them to experience less emotional reactivity 1 month (Studies 1 and 2) and 6 months (Study 2) after the intervention. Analyses using data from both studies indicated that expressive writing reduced physical symptoms indirectly through its effects on self-distancing and emotional reactivity [that is, expressive writing group (vs. comparison groups) → greater self-distancing → less emotional reactivity → fewer physical symptoms]. Finally, linguistic analyses using essays from both studies indicated that increased use of causation words and decreased use of negative emotion words and first-person singular pronouns predicted increases in self-distancing over time. These findings demonstrate that expressive writing promotes self-distancing and illustrate how it does so.

Randomized clinical trial of expressive writing on wound healing following bariatric surgery

Koschwanez, H., Robinson, H., Beban, G., MacCormick, A., Hill, A., Windsor, J., . . . Broadbent, E. (2017). Health Psychology, 36(7), 630-640.

Objective: Writing emotionally about upsetting life events (expressive writing) has been shown to speed healing of punch-biopsy wounds compared to writing objectively about daily activities. We aimed to investigate whether a presurgical expressive writing intervention could improve surgical wound healing. Method: Seventy-six patients undergoing elective laparoscopic bariatric surgery were randomized either to write emotionally about traumatic life events (expressive writing) or to write objectively about how they spent their time (daily activities writing) for 20 min a day for 3 consecutive days beginning 2 weeks prior to surgery. A wound drain was inserted into a laparoscopic port site and wound fluid analyzed for proinflammatory cytokines collected over 24 hr postoperatively. Expanded polytetrafluoroethylene tubes were inserted into separate laparoscopic port sites during surgery and removed after 14 days. Tubes were analyzed for hydroxyproline deposition (the primary outcome), a major component of collagen and marker of healing. Fifty-four patients completed the study. Results: Patients who wrote about daily activities had significantly more hydroxyproline than did expressive writing patients, t(34) = −2.43, p = .020, 95% confidence interval [−4.61, −0.41], and higher tumor necrosis factor–alpha, t(29) = −2.42, p = .022, 95% confidence interval [−0.42, −0.04]. Perceived stress significantly reduced in both groups after surgery. Conclusions: Expressive writing prior to bariatric surgery was not effective at increasing hydroxyproline at the wound site 14 days after surgery. However, writing about daily activities did predict such an increase. Future research needs to replicate these findings and investigate generalizability to other surgical groups.

Expressive writing can increase working memory capacity.

Klein, K., & Boals, A. (2001). Journal of Experimental Psychology: General, 130(3), 520-533.

The effect of emotional disclosure through expressive writing on available working memory (WM) capacity was examined in 2 semester-long experiments. In the first study, 35 freshmen assigned to write about their thoughts and feelings about coming to college demonstrated larger working memory gains 7 weeks later compared with 36 writers assigned to a trivial topic. Increased use of cause and insight words was associated with greater WM improvements. In the second study, students (n = 34) who wrote about a negative personal experience enjoyed greater WM improvements and declines in intrusive thinking compared with students who wrote about a positive experience (n = 33) or a trivial topic (n = 34). The results are discussed in terms of a model grounded in cognitive and social psychological theory in which expressive writing reduces intrusive and avoidant thinking about a stressful experience, thus freeing WM resources.