Table 2.

Final items and factor loadings from EFA and CFAs in our three samples

	Derivation sample	Longitudinal validation sample	Psychiatric validation sample
	EFA Loadings	CFA Loadings	CFA Loadings
COVID-19 contamination anxiety
I will infect myself with COVID-19	0.54	0.54	0.54
Please indicate how likely you think it is that you will be infected with COVID-19.	0.74	0.58	0.77
people close to me are infected with COVID-19.	0.88	0.89	0.65
I will infect other people with COVID-19.	0.79	0.72	0.73
COVID-19 hygiene measures
keeping at least 1.5 m distance from other people	0.67	0.67	0.63
coughing or sneezing into the crook of your arm or into a handkerchief	0.71	0.52	0.54
not touching mouth, eyes or nose with hands	0.81	0.80	0.58
regular washing of hands	0.93	0.79	0.63
washing hands extensively (for at least 30 s)	0.92	0.82	0.79
increased disinfection of hands and objects.	0.68	0.65	0.68
COVID-19 social distancing
cancelling private meetings and family visits	0.82	0.79	0.76
cancelling trips to other cities	0.90	0.85	0.69
avoiding visits to canteens and restaurants	0.87	0.79	0.82
avoiding touching (e.g. shaking hands or hugging) when greeting or saying goodbye to other people	0.78	0.74	0.47
moving your work to home office	0.71	0.64	0.39
COVID-19 anxiety buying
soap, detergent, cleaning products, washing powder, etc.	0.88	0.84	0.89
food (vegetables, lentils, rice, pasta...)	0.94	0.88	0.95
water (20 l per person)	0.79	0.73	0.85
toilet paper	0.84	0.82	0.92
cash	0.59	0.53	0.62
COVID-19 political restrictions
temporary closures of kindergartens, schools and universities	0.84	0.80	0.85
temporary border closures	0.74	0.67	0.71
temporary closures of playgrounds	0.85	0.75	0.90
temporary closure of bars, pubs, theatres, cinemas, etc.	0.87	0.78	0.72
temporary curfews	0.80	0.76	0.82
COVID-19 solidarity-based behaviours
donating blood	0.63	0.70	0.54
supporting people at risk, such as shopping for them or staying at home to protect people at risk to protect people at risk	0.86	0.77	0.88
supporting people who are experiencing existential hardship due to the current situation	0.87	0.79	0.86
offering help to close friends and family members	0.81	0.71	0.57
donating blood	0.77	0.80	0.65
COVID-19 post-traumatic stress disorder symptoms
have had upsetting dreams that replay part of the experience of the COVID-19 pandemic or are clearly related to it	0.51	0.61	0.60
have had powerful images or memories that sometimes come into my mind in which I feel the experience of the COVID-19 pandemic is happening again in the here and now	0.75	0.72	0.75
have avoided internal reminders of the experience of the COVID-19 pandemic (e.g. thoughts, feeling, or physical sensations)	0.97	0.82	0.64
have avoided external reminders of the experience of the COVID-19 pandemic (e.g. people, places, conversations, objects, activities, or situations)	0.92	0.73	0.79
have been “super-alert”, watchful, or on guard	0.45	0.56	0.67
COVID-19 sleep disturbances
difficulty falling asleep (<  30 min)	1.02	0.82	0.88
difficulty sleeping through the night	0.77	0.87	0.79
early morning awakening	0.70	0.74	0.74
COVID-19 substance use
have consumed substantially more alcohol than usual.	0.68
have smoked considerably more cigarettes than usual	0.86	0.61	0.66
have consumed considerably more drugs (e.g. tranquilizers, sleeping pills or stimulants) than usual	0.63	0.63	0.61
have felt a strong desire to consume addictive substances (alcohol, cigarettes, drugs)	0.87	0.90	0.84
have not been able to control my use of addictive substances (alcohol, cigarettes, drugs)	0.90	0.58	0.50
COVID-19 daytime structure
have maintained a regular daily routine	0.90	0.81	0.76
have planned the day as detailed as possible	0.80	0.79	0.95
have integrated sports and exercise into my daily life	0.39	0.55	0.58
COVID-19 social contacts
have maintained my social contacts (telephone, visits or video chats)	0.47	0.68	0.65
have enjoyed the time together with people close to me	0.74	0.50	0.50
COVID-19 inner resources
have sought stability in faith and/or religion	0.45
have focused on my inner strengths, resources, abilities and talents	0.59	0.87	0.72
have changed my attitudes about what is really important to me in life	0.64	0.39	0.70
COVID-19 political and institutional trust
have had the feeling that the political leadership was standing up for me	0.84	0.81	0.67
have perceived democracy as an effective form of government	0.85	0.75	0.77
have had the feeling that public institutions (e.g. police, judiciary) can be relied upon	0.78	0.79	0.82
have had the feeling that news and reports on the COVID-19 pandemic are being deliberately withheld	0.84	0.86	0.30
have perceived politicians as trustworthy	0.65	0.61	0.77
COVID-19 conspiracy beliefs
have had the feeling that false reports or untruths about the COVID-19 pandemic are being deliberately disseminated on public broadcasting (e.g. radio and television stations).	0.62	0.49	0.62
have had the belief that there are alternative or secret explanations for current events	0.80	0.89	0.84
have had the belief that there is a relation between what is happening and the production and testing of biological weapons	0.88	0.72	0.77
have had the belief that what is happening here is the effect of a struggle or competition between different superpowers	0.95	0.77	0.84
have had the belief that this infection serves to deliberately reduce the world population, since there are no longer enough resources for everyone	0.85	0.64	0.88
COVID-19 social cohesion
there is greater solidarity and cohesion in our society.	0.84	0.79
I am an integral part of our society or community.	0.61	0.61
our nation is growing closer together.	0.93	0.79