Table 2.

Univariable hazard ratios for each type of attrition in the initial phase

	Discontinuation		Withdrawal
	HR (95% CI)	p-value	HR (95% CI)	p-value
Age at baseline (per 10 years increase)	0.81 (0.73, 0.89)	<0.001	1.24 (1.04, 1.47)	0.02
Sex
Male	Reference		Reference
Female	0.91 (0.69, 1.21)	0.54	0.84 (0.52, 1.34)	0.46
Marital status
Married	Reference		Reference
Unmarried	1.32 (0.97, 1.79)	0.08	0.72 (0.41, 1.28)	0.26
Divorced/widowed	1.18 (0.73, 1.93)	0.50	0.88 (0.38, 2.06)	0.77
Highest completed educational level
Lower secondary education or apprenticeship	1.41 (0.52, 3.84)	0.50	2.44 (0.58, 10.31)	0.22
Still at upper secondary school	0.89 (0.62, 1.29)	0.54	1.56 (0.89, 2.76)	0.12
University entrance qualification	1.13 (0.81, 1.56)	0.48	1.07 (0.59, 1.95)	0.82
University degree	Reference		Reference
Frequency of Internet usage
Daily	Reference		Reference
Less than daily	1.23 (0.91, 1.67)	0.19	2.03 (1.26, 3.27)	0.004
Self-rated health status
Fair/poor	0.93 (0.55, 1.59)	0.80	1.57 (0.67, 3.68)	0.30
Good	1.09 (0.81, 1.47)	0.56	1.73 (1.03, 2.92)	0.04
Excellent/very good	Reference		Reference
WHO-5 well-being index (per 10 points increase)	0.96 (0.89, 1.03)	0.24	0.96 (0.85, 1.09)	0.57
PSS score (per 1 point increase)	1.07 (1.02, 1.12)	0.002	0.97 (0.89, 1.05)	0.46
ID-Screen (per 1 point increase)	1.03 (0.99, 1.07)	0.10	1.01 (0.95, 1.08)	0.73
Time between invitation and return of the filled informed consent form (per week)	1.1 (1.04, 1.17)	<0.001	0.98 (0.82, 1.16)	0.78
Had to be reminded to fill in the first online questionnaire (A)
Yes	1.85 (1.27, 2.7)	0.001	0.82 (0.33, 2.05)	0.68
No	Reference		Reference