Table 4.
Independent variables and instruments used for their assessment in the present study.
| Sociodemographic variables | Sex | Boy and girl. Level of measurement: categorical variable. | |
| Age | 13–16 years. Level of measurement: continuous variable. | ||
| Type of educational center | Public and private. Level of measurement: categorical variable. | ||
| Habitat | Urban and rural. Level of measurement: categorical variable. | ||
| School context variables | Perceived academic achievement | They were asked: “in your opinion, what does your teacher think about your school performance compared to your classmates” (this question was created by the HBSC study). This question is answered on a 4-point Likert scale, ranging from 1, below average, to 4, very good. Level of measurement: quantitative variable. | |
| Feelings toward school | The following question: “how do you feel about school at the present?” (this question was created by the HBSC study). Four response options were available on a 4-point Likert scale from 1, I don't like it at all, to 4, I like it a lot. Level of measurement: continuous variable. | ||
| Teacher support | It was assessed by means of the following three items: “I feel that my teachers accept me as I am,” “I feel that my teachers care about me as a person,” and “I feel a lot of trust in my teacher,” with a Cronbach's alpha of 0.84. Items were answered on a 5-point Likert scale, from 1, I completely disagree, to 5, I completely agree (Torsheim et al., 2000). Level of measurement: continuous variable. | ||
| Peer context variables | Perceived social support | It was assessed by means of the Multidimensional Scale of Perceived Social Support (MSPSS; Zimet et al., 1988). This scale consists of the following four items: “my friends really try to help me,” “I can count on my friends when things go wrong,” “I have friends with whom I can share my joys and sorrows,” and “I can talk about my problems with my friends,” Items are answered on a 7-point Likert scale, from completely disagree (1) to completely agree (7), with a Cronbach's alpha of 0.98. Level of measurement: continuous variable. | |
| Models of behavior in the peer group | It was assessed by means on a scale developed by the HBSC study network and validated by Gaspar de Matos et al. (unpublished manuscript). Adolescents were asked about the frequency of 8 different behaviors in their group of friends, including both positive (such as “do well in school,” “participate in sports activities with other kids,” “participate in cultural activities other than sports” and “get along well with parents”) and negative (such as “smoke cigarettes,” “drink alcohol,” “get drunk,” and “consume drugs to get high”) behaviors. Items were answered on a Likert scale from 1, never or almost never, to 3, often, with a Cronbach's alpha of 0.70. The items corresponding to negative behaviors were reverse-coded, so that a higher score on this scale represents a higher presence of positive models of behavior in the peer group. Level of measurement: continuous variable. | ||
| Satisfaction with friendships | Measure adapted by the HBSC network from the Cantril's Ladder on life satisfaction scaled from 0 to 10 (Cantril, 1965), but referring specifically to satisfaction with friendships. Level of measurement: quantitative variable. | ||
| Having been bullied | It was assessed by means of the Revised Bully/Victim Questionnaire (Olweus, 1996). The response options ranged from 1, I haven't been bullied in school in the past 2 months, to 5, multiple times a week. Level of measurement: quantitative variable. | ||
| Having bullied others | Also assessed by means of the Olweus (1996) questionnaire and with similar response options. Level of measurement: quantitative variable. | ||
| Lifestyle variables | Eating habits | Breakfast frequency | Adolescents were asked how many days a week they typically ate breakfast (something more than a glass of milk or juice), with the corresponding response values ranging from 1 to 7 days. In addition, they also answered questions on how many times a week they typically ate two specific types of foods: fruits and snacks. These questions were created by the HBSC study. The response options varied from 1, never, to 7, every day, more than once. Level of measurement: quantitative variable. |
| Fruit consumption | |||
| Snack consumption | |||
| Physical activity | MVPA | Adolescents were asked about their level of Moderate to Vigorous Physical Activity (MVPA), as indicated by the number of days in which they felt physically active during a total of at least 60 min a day over the last 7 days. The response options ranged from 0 to 7 days (Prochaska et al., 2001). In addition, they were asked about their level of Vigorous Physical Activity (VFA), assessed in the HBSC study by the frequency with which the adolescents, in their free time outside of school hours, engaged in some type of physical activity that made them sweat or out of breath. The response options on a Likert scale ranged from 1, never, to 7, every day. Level of measurement: quantitative variable. | |
| VFA | |||
| Dental hygiene | Adolescents were asked how often they brushed their teeth (these questions were created by the HBSC study), with the following response options: never; less than once a week; at least once a week but not daily; once a day; and more than once a day. Level of measurement: quantitative variable. | ||
| Substance use | Tobacco use | Three questions referring to the frequency of substance use over the past 30 days were included. These items have been adapted from the questions included in the European School Survey Project on Alcohol and Other Drugs (Hibell et al., 2000). Specifically, adolescents were asked about the number of days, out of past 30 days, in which they had smoked cigarettes, had drank alcohol and had smoked cannabis (hash or marijuana, “joints”). These items were answered on a 7-point Likert scale, from 1, never, to 7, 30 days. Level of measurement: quantitative variable. | |
| Alcohol use | |||
| Cannabis use | |||
| Psychological variables | Sense of coherence | This construct was assessed by means of the SOC-13 scale (Antonovsky, 1987). It consists of 13 items, such as “has it happened in the past that you were surprised by the behavior of people whom you thought you knew well?,” and “how often do you have the feeling that there's little meaning in the things you do in your daily life?.” Questions are answered on a 7-point Likert scale, with a Cronbach's alpha of 0.77. The SOC-13 scale has shown good reliability and validity in different countries (Lindström and Eriksson, 2010). Level of measurement: continuous variable. | |
| Emotional regulation | It was assessed by means of the impulsiveness/emotion-control subscale from the reduced version of the Emotion Regulation Index for Children and Adolescents scale (ERICA; MacDermott et al., 2010). This subscale comprises 8 items (for example, “I have angry outbursts,” “I have trouble waiting for something I want”) and it is answered on a 5-point Likert scale, from 1, totally agree, to 5, totally disagree. The Cronbach's alpha was of 0.84. Level of measurement: continuous variable. | ||
| Curiosity and Exploration | It was assessed by means of the Curiosity and Exploration Inventory-II (Kashdan et al., 2009). It is a scale with 10 items (some examples are: “I am at my best when doing something that is complex or challenging,” “I am the kind of person who embraces unfamiliar people, events, and places,” or “I like to do things that are a little frightening”) with 5 response options on a Likert scale, from 1, a little or none, to 5, a lot. The Cronbach's alpha was of 0.87. Level of measurement: continuous variable. | ||
| Perceived body image | It was assessed with an item created for the HBSC study. Specifically, they are asked “do you think your body is…?” and the response options on a 5-point Likert scale ranged from 1, much too fat, to 5, much too thin. Level of measurement: ordinal variable. | ||
| Satisfaction with body image | It was assessed by means of the subscale of feelings and attitudes toward the body of the Body Investment Scale (BIS; Orbach and Mikulincer, 1998). This subscale consists of 6 items (“I am frustrated with my physical appearance,” “I am satisfied with my appearance,” “I hate my body,” “I feel comfortable with my body,” “I feel anger toward my body,” and “I like my appearance in spite of its imperfections”), and is answered on a 5-point Likert scale, from 1, totally agree, to 5, totally disagree. The Cronbach's alpha was of 0.89. Level of measurement: continuous variable. | ||
| Socioeconomic variables | Father educational level | Father's and mother's educational level and perceived family wealth were assessed with three questions created by the HBSC study. Educational level was measured on a 4-point Likert scale, from 1, never studied (does not know how to read nor write, or does so with difficulty) to 4, university studies, either finished or unfinished. The level of perceived family wealth was assessed by asking “how well off do you think your family is?.” The question was answered on a 5-point Likert scale, from 1, not at all well off, to 5, very well off. Level of measurement: quantitative variable. | |
| Mother educational level | |||
| Perceived family wealth | |||