There is quite a lot of research on writing therapy and expressive writing more generally. As you note, much of this research relates to writing about negative emotional experiences. There is some support for the positive mental health benefits in writing about traumatic events (e.g., see the meta-analysis by Smyth, 1998).
While the interventions are focused on writing about negative events, the intervention
Positive psychology and writing
I have read about a few specific positive psychology writing interventions, such as those mentioned here:
- Keep a gratitude diary: Take the time each day to write down three things that went well and why. This causes psychological well-being
levels to increase in a lasting way.
- Thank a mentor: Write a letter of thanks to someone to whom you owe a debt of gratitude such as a teacher or grandparent. Then visit the
person and read the letter to them. People who do this are measurably
happier for more than a month.
- Learn to forgive: Let go of anger and resentment by writing a letter of forgiveness to a person who has wronged you. Inability to forgive is associated with persistent rumination.
Toepfer and Walker (2009) discuss writing letters of gratitude. They cite several studies showing positive effect, stating that
Expressive writing studies are plentiful and the once anemic domain of
letter writing as a vehicle for improving health has seen a recent
surge of interest (King, 2001; Sheldon & Lyubomirsky, 2006a; Seligman
et al., 2005; Lyubomirsky, Dickerhoof, Boehm, & Sheldon, 2009). For
example, VandeCreek, Janus, Pennebaker and Binau (2002) asked
participants to pray and write letters to God and found that both
prayer and the letters increased insight and positive emotion, more
so than simple written descriptions, where a single letter to God had
the most impact. The authors explained that the act of praying or
explaining to another (in this case in a letter to God) was more
conducive to personal insight and greater positive emotional
formulations about life events. In other words, writing a letter to
God was found to improve participant’s positive feelings about life
Watkins, Woodward, Stone and Kolts (2003) conducted a study
that examined mood changes as the result of various gratitude
inductions, one of which was a letter writing condition. Their
findings revealed that writing a gratitude based letter produced a
positive affect increase compared to the other gratitude inductions
(Watkins et al., 2003).
Burton and King found positive effects from getting participants to write about positive experiences. They also summarise some of the literature noting that
research has begun to explore a variety of writing topics that
might be associated with health beneﬁts that do not focus exclusively
on negative experience. King and Miner (2000) found that writing only
about the positive aspects of a traumatic experience was associated
with the same health beneﬁts as writing about trauma. King (2001)
found that individuals who wrote about their best possible future
selves showed physical health beneﬁts as well as enhanced
psychological well-being after writing.
Burton and King's instructions were:
Think of the most wonderful experience or experiences in your life,
happiest moments, ecstatic moments, moments of rapture, perhaps from
being in love, or from listening to music, or suddenly ‘‘being hit’’
by a book or painting or from some great creative moment. Choose one
such experience or moment. Try to imagine yourself at that moment,
including all the feelings and emotions associated with the
experience. Now write about the experience in as much detail as
possible trying to include the feelings, thoughts, and emotions that
were present at the time. Please try your best to re-experience the
As for a mechanism of operation, Wing et al present the following ideas:
Writing about nontraumatic events likely shares some effects with
writing about traumatic events. Writing about any meaningful aspect of
life may promote cognitive processing, encouraging the examination,
understanding, and assimilation of emotions that might otherwise be
left unscrutinized (Pennebaker, 2002; Pennebaker, Mayne, & Francis,
1997; Pennebaker & Seagal, 1999). Writing about a meaningful topic may
result in enhanced emotional regulation, related to perceptions of
self-efficacy and control over emotional experiences (Greenberg,
Wortman & Stone, 1996; King, 2001, 2002; Lepore et al., 2002). Writing
may afford the writer the opportunity to gain a sense of mastery over
his or her emotions and to clearly identify priorities, preferred
outcomes, and goals (King, 2001).
- 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. PDF
- King, L. A. (2001). The health beneﬁts of writing about life goals. Personality and Social Psychology Bulletin, 27(7), 798–807.
- King, L. A., & Miner, K. N. (2000). Writing about the perceived beneﬁts of traumatic events: Implications
for physical health. Personality and Social Psychology Bulletin, 26(2), 220–230.
- Wright, J. (2002). Online counselling: Learning from writing therapy. British Journal of Guidance and Counselling, 30(3), 285-298. PDF
- SMYTH, J.M.(1998).Written emotional expression: effect size, outcome types, and moderating variables.
Journal of Consulting and Clinical Psychology, 66(1), 174±184. PDF
- Toepfer, S., & Walker, K. (2009). Letters of gratitude: Improving well-being through expressive writing. Journal of Writing Research, 1(3), 181-198. PDF
- Wing, J. F., Schutte, N. S., & Byrne, B. (2006). The effect of positive writing on emotional intelligence and life satisfaction. Journal of clinical psychology, 62(10), 1291-1302.