Differential association between affect and somatic symptoms at the between- and within-individual level

Abstract

Objectives: The established between-subjects associations between affect and somatic symptoms have often been interpreted as indicating a causal effect of affect on somatic symptoms, but it is doubtful whether this is valid. In this study, we evaluate the association between positive affect (PA), negative affect (NA), and somatic symptoms at both the between- and within-subject level. Design and methods: Diary data were collected in the context of an online study called ‘HowNutsAreTheDutch’. Participants filled out an online questionnaire, three times a day for 30 consecutive days. A mixed linear model was used to test the contemporaneous and lagged associations between affect and somatic symptoms. Results: Five hundred and eighty-six participants (481 females, median age 39.6 years [range 18.1–71.4]) were included with a total number of 28,264 completed questionnaires. At the between-subjects level, a positive association between NA and somatic symptoms was found (B =.60, p