Health effects of expressive writing on stressful or traumatic experiences - a meta-analysis

In his theory of emotional inhibition Pennebaker [44] proclaimed that the disclosure of stressful or traumatic experiences reduces the probability of detrimental health effects. In his experimental paradigm disclosure was induced by asking the participants to write about their deepest thoughts and feelings relating to a stressful event during 3 to 4 writing sessions of 15 to 20 minutes. Based on a meta-analysis of 13 studies Smyth [58] reported an average effect size of d=0.47 for various health related variables. Considering the great number of studies published since then, the aim of our study was to update the state of evidence regarding the effects of expressive writing on health, including only randomized controlled trials in our analysis. From 42 trials fulfilling the inclusion criteria 30 could be used for the meta-analysis. Neither regarding somatic nor psychological health variables significant effect sizes were found. Various exploratory analyses (e.g. restriction to clinical samples) also resulted in non-significant effect sizes, except for one rendering a very small effect size. Results of our meta-analysis lead to the conclusion that expressive writing has minor or no effects on the subject’s health contrary to earlier findings.