Table 2. Comparisons of participants (n = 1,157) and nonparticipants (n = 3,411) of the 6-month follow-up; n (%); mean [SD].

	Participants n = 1,157+	Nonparticipants n = 3,411+	p
Interest in psychotherapy	193 (16.7)	336 (9.9)	<0.001
Age: Years	52.49 [15.53]	45.75 [16.02]	<0.001
Women	667 (57.6)	1708 (50.1)	<0.001
Partnership status: Living with a partner	768 (67.1)	2051 (60.8)	<0.001
Level of education: University entrance qualification	511 (44.6)	1374 (40.5)	0.015
ASA Classification++a)			<0.001
ASA I	172 (24.1)	773 (34.1)
ASA II	416 (58.2)	1218 (53.8)
ASA III	125 (17.5)	270 (11.9)
ASA IV	2 (0.3)	5 (0.2)
Surgical field ++			0.028
Abdomino thoracic surgery	283 (39.6)	868 (38.3)
Peripheral surgery	235 (32.9)	660 (29.1)
Neuro-, head and neck surgery	197 (27.6)	738 (32.6)
BSI GSI, severity of psychological distress b)	0.34 [0.37]	0.33 [0.39]	0.168
Self-rating of current subjective health c)	64.31 [24.78]	64.22 [27.49]	0.917
WHO-5 d)	14.54 [5.83]	14.44 [5.79]	0.587
PHQ-2 e)	1.48 [1.44]	1.40 [1.40]	0.094
CES-D f)	9.98 [6.90]	9.56 [6.56]	0.078
BSI depression b)	0.32 [0.53]	0.30 [0.52]	0.377
GAD-2 g)	1.35 [1.51]	1.23 [1.41]	0.013
BSI anxiety b)	0.39 [0.47]	0.35 [0.47]	0.008
BSI interpersonal sensitivity b)	0.35 [0.53]	0.34 [0.53]	0.347
BSI phobic anxiety b)	0.18 [0.38]	0.17 [0.37]	0.544
AUDIT sum score h)	2.79 [3.15]	3.09 [3.52]	0.007
AUDIT-C: Risky alcohol consumption h)	2.34 [1.96]	2.50 [2.13]	0.015

⁺Number ranges for the specific variables from 1,123 to 1,157 (participants) and from 3,236 to 3,411 (nonparticipants) because of missing data.

⁺⁺Data for ASA and surgical field are available for the implementation phase; numbers account to 715 (participants), and 2266 (nonparticipants) because of missing data.

^a)ASA (American Society of Anesthesiologists) physical status classification: (I) Healthy patient; (II) Mild systemic disease, no functional limitation; (III) Severe systemic disease with definite functional limitation; (IV) Severe systemic disease that is a constant threat to life;

^b)BSI: Brief Symptom Inventory; GSI: General severity index;

^c)Visual analogue scale of the EQ-5D, 0 to 100 with higher scores indicating better subjective health;

^d)WHO-5: World Health Organization 5-item Well-Being Index;

^e)PHQ-2: Patient Health Questionnaire-4, depression subscale;

^f)CES-D: Center for Epidemiologic Studies Depression Scale;

^g)GAD-2: Patient Health Questionnaire-4, anxiety subscale;

^h)AUDIT: Alcohol Use Disorder Identification Test, AUDIT-C: AUDIT subscore for risky alcohol consumption.