Objective: To examine whether the personality dimensions, neuroticism and alexithymia, and the affective state dimensions measuring negative and positive affect significantly contributed to changes over time in the number of medically unexplained symptoms (MUS) reported.
Methods: A total of 318 patients, presenting to their primary care physician with MUS, participated in the study. Logistic regression analyses were conducted to assess to what extent neuroticism, alexithymia, negative affect and positive affect independently contributed to (1) increase vs. decrease in the number of symptoms reported, and (2) the presence of a consistently high number of MUS over a 6-month follow-up period.
Results: Negative affect was the strongest determinant of changes in the number of symptoms reported. In addition, low positive affect significantly contributed to changes in the number of symptoms over time. Next to negative affect, the dimension of alexithymia measuring difficulty in identifying feelings (DIF) was found to be an independent predictor of a consistently high number of MUS. Neither neuroticism nor general alexithymia independently contributed to changes in the number of symptoms over time or to symptom persistence.
Conclusions: Negative affect is an important determinant of MUS, because it contributes both to symptom evolution and symptom persistence. Positive affect has a beneficial effect on somatic symptom evolution, whereas the alexithymia dimension measuring DIF clearly contributes to the prediction of symptom persistence.