*2.2. Study Participants*

With a target population of 27,103 nurses, a confidence level of 99%, a margin of error of 5%, and percentage of our sample picking a particular answer = 50% (we used 50%, which is conservative and provides the largest needed sample size for the given level of accuracy), the minimum sample of the study was set at 651 individuals A total of 850 nurses were invited to answer the questionnaires and 660 agreed to participate in the survey.

## *2.3. Measurement Tools*

Demographic and social data from study participants included age, gender, and marital status. Professional information included work experience.

#### *2.4. Copenhagen Burnout Inventory*

The Copenhagen Burnout Inventory (CBI) is a tool for measuring personal and occupational burnout, consisting of 19 questions. Answers include "always, often, sometimes, rarely, and never/almost never" or "to a very high degree, to a high degree, somewhat, to a low degree and to a very low degree". The response options are coded in scores of 100, 75, 50, 25, and 0. Possible score range for the burnout scales is 0–100 [29]. Higher scores indicate a higher degree of exhaustion.

The questionnaire includes three subscales:


For the needs of the study, the Greek adaptation of the questionnaire was used. In reliability analysis, Cronbach's alpha exceeds 0.7 for all subscales indicating a high level of internal consistency [30]. A score higher than 50 was considered as indicative of burnout [31,32].

#### *2.5. Beck's Depression Inventory*

Beck's Depression Inventory (BDI) measures the cognitive, emotional, behavioral, and physical manifestations of a person's depression over the past week. It consists of 21 topics which are scored on a scale of 0–3 [33]. The total score is obtained after the sum of the ratings of the 21 topics. The stratification of the severity of depressive symptoms is as follows: 0–9 = without depression, 10–15 = mild depression, 16–23 = moderate depression and ≥24 = severe depression. The scale, in its Greek form [22], is a short and reliable tool for measuring depression and has been used by nursing staff in Greece [34]. Internal consistency and reliability are high and retest reliability ranges between 0.48–0.86 for clinical groups and 0.60–0.90 for non-clinical populations. Validity in relation to an external criterion for depression, such as the clinical diagnosis, is considered to be satisfactory [35].

#### *2.6. Sense of Coherence Questionnaire-13*

The Sense of Coherence questionnaire (SOC) was developed by Antonovsky to assess how people manage stressful situations and stay well [36]. The SOC-13 scale consists of 13 items, each of which is rated on a Likert scale, ranging from 1 ("very common") to 7 ("very rare or never"). The scale includes three dimensions: comprehensibility (five items, measuring the person's perception of the internal and external elements of its environment as structured and predictable); manageability (four items, referring to the person's ability to meet the demands of stressful environment successfully); and meaningfulness (four items, measuring the person's ability to view those demands as worthy challenges, thus referring to its motivation) [37,38]. Scores range from 13 to 91, with the highest scores

indicating a stronger SOC. In this study we used the short version of SOC-13, which has been standardized in the Greek population and seems to be a reliable and valid instrument, with a Cronbach alpha of 0.83 [37].
