Table 1 Description of the mental health indicators, used as outcomes, based on the questions in the Belgian Health Interview Survey 2018

GHQ-12

Indicator of mental well-being.

12 questions

1. 1. The sum (from 0 to 12) represents the global GHQ-score. The higher the score, the more change of physiological complaints.

Answers: ‘better than usual’, ‘as good as usual’, ‘less than usual’, ‘much less than usual’

2. 1. A cut-off point of [2+] is used to identify those participants with at least 2 ‘abnormal’ psychological complaints, indicating a possible psychopathology.

Ranking: [0 0 1 1]

3. A cut-off point of [4+] is used to identify those participants with at least 4 ‘abnormal’ psychological complaints, indicating the more severe cases.

Cantril scale

Life satisfaction

On a scale from 0 to 10, 0 indicating ‘completely dissatisfied’ and 10 indicating ‘completely satisfied’, how satisfied are you with your life?

1. The score indicates the life satisfaction. The higher the score, the more someone is satisfied with their life.

2. The scale is divided into three groups: 0 = low satisfaction (0–5), 1 = average satisfaction (6–8), 2 = high satisfaction (9–10).

SF-36

Indicator of the positive psychological health (vital energy)

4 questions

1. 1. The average of the scores is converted to a scale from 0 to 100. The higher the score, the higher the vitality.

Answers: ‘always’, ‘most of the time’, ‘sometimes’, ‘rarely’, ‘never’

Ranking: [5 4 3 2 1] for the first two questions and [1 2 3 4 5] for the last two questions.

2. A dichotomous score indicates those who have an energy and vitality well above average (calculated as the average of all participants + the standard deviation)

SCOFF

Indicator in regard to possible eating disorders

5 yes or no questions

Participants are identified as having an eating disorder when they answered at least twice ‘yes’.

PHQ-9

Indicator of a depressive disorder and depression severity score

9 questions

1. 1. A dichotomous indicator is used to identify who suffers from major depression syndrome (MDD).

Answers: ‘not at all’, ‘several days’, ‘more than half the days’ and ‘nearly every day’

2. A dichotomous indicator is used to identify who suffers from any type of depression other than MDD.

3. The combination of both is used to identify participants with any type of depression.

4. To indicate the severity score, the participants are divided into five groups: 0 = no depression, 1 = mild depression, 2 = moderate depression, 3 = moderate/severe depression, 5 = severe depression.

GAD-7

Indicator of general anxiety disorder and anxiety severity score

7 questions

1. A cut-off point of [10+] is used to identify who suffers from a general anxiety disorder.

Answers: ‘not at all’, ‘several days’, ‘more than half the days’ and ‘nearly every day’

2. 1. To indicate the severity score, the participants are divided into four groups: 0 = no anxiety, 1 = mild anxiety, 2 = moderate anxiety, 3 = severe anxiety.

Ranking: [0 1 2 3]