Assessing prolonged grief symptoms using experience sampling methodology: The development of the prolonged grief symptoms - short ecological assessment (PGS-SEA) scale

Early grief reactions have been hypothesized to fluctuate within persons and to be one of the strongest predictors of Prolonged Grief Disorder (PGD). Experience Sampling Methodology (ESM) offers an opportunity to examine (early) PGD dynamics in daily contexts. For this, however, a brief and valid ESM scale is needed to accurately assess PGD symptoms in everyday life. We investigated the psychometric properties of ESM items developed to assess momentary prolonged grief symptoms in daily life (ESM-PGD). Additionally, we aimed to create a valid brief scale for future ESM studies. Bereaved adults (N = 169) whose loved ones died 3-6 months earlier completed 11 ESM-PGD items based on 10 PGD symptoms, as defined in DSM-5-TR, five times a day for 14 consecutive days at semi-random intervals. We performed multilevel confirmatory factor analysis (MCFA), calculated root-mean-square of successive differences (RMSSD) and intraclass correlations (ICC), and conducted correlational analyses of ESM-PGD items with related mental health symptoms (e.g., depression) to identify the best-performing items. MCFA confirmed that the hypothesized one-factor model fits the data well with good composite reliability at the between- and within-person levels. All ESM-PGD items were able to distinguish between people with and without early PGD. Examination of within-person level factor loadings, ICCs and RMSSDs revealed that not all ESM-PGD items were able to capture fluctuations of momentary PGD symptoms. The best-performing items were selected, resulting in a valid 2-item Prolonged Grief Symptoms - Short Ecological Assessment (PGS-SEA) scale for assessing PGD in daily life to facilitate ESM-research on PGD.