Purpose in Life in ALS Patient-Caregiver Dyads: A Multilevel Longitudinal Analysis

Objective: Eudaemonic positive psychological health (PPH), such as purpose in life (PIL), may be maintained more than hedonic PPH, such as quality of life (QOL), for patients with amyotrophic lateral sclerosis (ALS) and their caregivers across the disease course. Furthermore, patients' and caregivers' PPH may impact one another. The present study examined (a) PIL and QOL variance structures; (b) PIL and QOL trajectories from diagnosis, approaching death, with disease severity; and (c) between-dyad and within-dyad relationships for PIL and QOL in patients with ALS and their caregivers. Method: PIL and QOL were assessed in patient-caregiver dyads (N = 110) up to 7 times over 18 months. Results: Multilevel models revealed the proportion of variance attributed to stable between-person differences was higher for PIL (patients = 74%; caregivers = 76%) than QOL (patients = 60%; caregivers = 55%). PIL and QOL declined in relation to disease severity and time. For PIL, proximity to diagnosis and death moderated within-person change; decline was generally faster following diagnosis and approaching death. Longitudinal within-dyad relationships revealed that patients' fluctuations in PIL were mirrored in their caregiver and vice versa. Conclusions: PIL was more stable than QOL and was therefore a potential psychological resource for patients and caregivers. Critical periods-after diagnosis and approaching death-accompanied more rapid PIL decline. QOL was also impacted by proximity to critical periods. PIL within-dyad relationships may reflect a shared disease experience. Psychological intervention focused on enhancing purpose, particularly during critical periods, is a promising direction for future study.