1. Pennebaker & Beall (1986)

Finding: Writing about emotional experiences improved psychological health and reduced physical symptoms versus neutral writing.
Citation:
Pennebaker, J. W., & Beall, S. K. (1986). Confronting a traumatic event: Toward an understanding of inhibition and disease. Journal of Abnormal Psychology, 95(3), 274–281.

2. Pennebaker, Kiecolt-Glaser & Glaser (1988)

Finding: Expressive writing led to stronger immune function and fewer illness-related doctor visits.
Citation:
Pennebaker, J. W., Kiecolt-Glaser, J. K., & Glaser, R. (1988). Disclosure of traumas and immune function: Health implications for psychotherapy. Journal of Consulting and Clinical Psychology, 56(2), 239–245.

3. Francis & Pennebaker (1992)

Finding: People who journaled about stressful experiences sought significantly fewer medical visits in the following 6 months.
Citation:
Francis, M. E., & Pennebaker, J. W. (1992). Putting stress into words: The impact of writing on physiological, absentee, and self-reported emotional well-being measures. Psychosomatic Medicine, 54(5), 488–492.

4. Smyth (1998) – Meta-analysis

Finding: Across randomized trials, expressive writing reliably improved physical health, well-being, and stress outcomes.
Citation:
Smyth, J. M. (1998). Written emotional expression: Effect sizes, outcome types, and moderating variables. Journal of Consulting and Clinical Psychology, 66(1), 174–184.

5. Klein & Boals (2001)

Finding: Journaling increased working memory capacity, improving mental organization and cognitive performance.
Citation:
Klein, K., & Boals, A. (2001). Expressive writing can increase working memory capacity. Journal of Experimental Psychology: General, 130(3), 520–533.

6. Burton & King (2004)

Finding: Writing about positive experiences for just a few minutes a day improved mood and overall health weeks later.
Citation:
Burton, C. M., & King, L. A. (2004). The health benefits of writing about intensely positive experiences. Journal of Research in Personality, 38(2), 150–163.

7. Sloan & Marx (2004)

Finding: Structured written disclosure reduced trauma symptoms and emotional distress versus control writing.
Citation:
Sloan, D. M., & Marx, B. P. (2004). A closer examination of the structured written disclosure procedure. Journal of Consulting and Clinical Psychology, 72(2), 165–175.

8. Gortner, Rude & Pennebaker (2006)

Finding: Adults with major depressive disorder experienced reductions in depressive symptoms through journaling.
Citation:
Gortner, E.-M., Rude, S. S., & Pennebaker, J. W. (2006). Benefits of expressive writing in lowering rumination and depressive symptoms. Journal of Affective Disorders, 93(1–3), 141–147.

9. Frattaroli (2006) – Meta-analysis

Finding: Reviewing 146 studies, expressive writing showed consistent psychological and physical health benefits.
Citation:
Frattaroli, J. (2006). Experimental disclosure and its moderators: A meta-analysis. Psychological Bulletin, 132(6), 823–865.

10. Lieberman et al. (2007)

Finding: Labeling feelings in writing reduced amygdala activity — meaning lower emotional reactivity and better regulation.
Citation:
Lieberman, M. D., et al. (2007). Putting feelings into words: Affect labeling disrupts amygdala activity in response to affective stimuli. Psychological Science, 18(5), 421–428.

11. Matthews (Dominican University, 2007–2011 range)

Finding: Participants who wrote down their goals were 42% more likely to achieve them.
Citation:
Matthews, G. (Dominican University of California). The Impact of Commitment, Accountability, and Written Goals on Goal Achievement.
(Published as a research summary/white paper, widely cited; not a peer-reviewed journal article.)

12. Travagin, Margola & Revenson (2015) – Meta-analysis

Finding: Among adolescents, expressive writing reduced internalizing symptoms (anxiety/depression) and improved mood.
Citation:
Travagin, G., Margola, D., & Revenson, T. A. (2015). How effective are expressive writing interventions for adolescents? A meta-analytic review. Clinical Psychology Review, 36, 42–55.