ABSTRACT
Spain, one of the European countries most affected by the COVID-19 pandemic, underwent a strict lockdown between March and May 2020. This study examines longitudinally the evolution of both psychological inflexibility and mental health symptoms in a sample of college students from the beginning and throughout the end of the mandated lockdown period. We present the results from 197 participants who responded to an online survey at least at two of three data-collection waves scheduled at the beginning (N = 226), halfway (N = 172), and end (N = 188) of the lockdown. The analyses revealed that psychological inflexibility and symptomatology increased over time, and that inflexibility at the beginning of the lockdown indirectly predicted self-reported symptoms at the end of the lockdown via autoregressive parallel paths that also connected cross-sectionally to reveal that changes in inflexibility were predictive of changes in mental health. These results present a dynamic and robust relationship between psychological inflexibility and mental health symptoms throughout a relatively long and presumably stressful period of time.