the forgotten branch. journaling and immune function

The arc of the expressive-writing literature most readers know is psychological. Mood improves, depressive symptoms drop, anxiety eases. The arc that runs alongside it, started in the same lab in 1988 and extended for thirty-five years across viral antibodies, vaccine response, CD4 counts and skin-tissue healing, is immunological. It is genuinely surprising, partially replicated, and almost entirely absent from the consumer journaling discourse.

the claim that started the branch

In 1988 Pennebaker, Kiecolt-Glaser and Glaser published Disclosure of traumas and immune function in the Journal of Consulting and Clinical Psychology. [5] Fifty healthy undergraduates were randomly assigned to write for twenty minutes on four consecutive days, either about the most traumatic experiences of their lives or about trivial assigned topics. Blood was drawn the day before writing, an hour after the final session, and six weeks later. Lymphocytes were stimulated with two T-cell mitogens, PHA and ConA, and proliferation measured.

The headline result was the PHA Condition × Day interaction, F(2, 80) = 3.36, p = .04. Trauma writers' lymphocytes proliferated more vigorously in response to the mitogen than controls' did, both immediately after writing and at six-week follow-up. ConA, the second mitogen, trended in the same direction but did not clear significance in the full sample. Health-center visits, tracked independently of the immune assay, showed a parallel Condition × Time interaction, F(1, 48) = 4.20, p < .05.

The results indicate that writing about traumatic experience has positive effects on the blastogenic response of T-lymphocytes to two mitogens, on autonomic levels, on health center use, and on subjective distress.

The paper is fifty undergraduates and one significant interaction on one of two mitogens. It is also, in 1988, the first time anyone had asked whether a writing assignment moved a cellular-immune marker in a randomised trial. The branch grew from there.