Here one time, gone the next: Fluctuations in support received and provided predict changes in relationship satisfaction across the transition to parenthood.

Extant research has demonstrated that higher mean (average) levels of social support often produce robust relational benefits. However, partners may not maintain the same level of support across time, resulting in potential fluctuations (i.e., within-person variations across time) in support. Despite the theorizing and initial research on fluctuations in relationship-relevant thoughts, feelings, and behaviors, little is known about (a) who is most likely to fluctuate in support and (b) the degree to which fluctuations, in combination with and beyond mean levels, impact relationships across time. The current preregistered research examined two dyadic longitudinal samples of first-time parents undergoing the transition to parenthood, a chronically stressful time that often entails the provision and receipt of support involving one's partner. Across both studies, we found that individuals who reported greater mental health problems, more situational stress, and more destructive dispositional attributes tended to report lower mean levels and higher fluctuations in provided and received support at subsequent assessments. Moreover, we found that greater fluctuations in perceptions and observations of support predicted decreases in relationship satisfaction over time, above and beyond the effect of mean levels. Implications for theory and studying nonlinear effects in relationships are discussed. (PsycInfo Database Record (c) 2023 APA, all rights reserved).