Independent variable. COVID lockdown: a variable “Days since first lockdown (15th of March, 2020)” was created and converted into a categorical variable with categories coinciding with every month of the observation period (category 1 =April 2020; category 24 = July 2021). Due to the timing of Lifelines assessments, some months had very few observations (e.g. August 2020), or no observations at all (e.g. February 2021). These categories were merged with the previous month (e.g. “July/August 2020″) or dropped (February 2021).
