Participants
The participants in the present study were part of wave 1 and wave 2 of the “G(F)OOD together” research project, a longitudinal study on Dutch adolescents’ and their parents’ health behavior. This ongoing longitudinal study has four waves of data collection: fall 2017, spring 2018, spring 2019 and (as planned before Corona-crisis broke out) spring 2020. This paper reports on the first two waves. Parental consent was provided for 718 children. In the first wave 667 adolescents from six secondary schools in the South and the East of the Netherlands participated and in the second wave 688 adolescents participated (95.8% participated in both waves). Because some adolescents were absent at wave 1 due to illness or other appointments, more adolescents actually participated in wave 2. Adolescent boys (W1, n = 314; W2, n = 320) and girls (W1, n = 353; W2, n = 368) were approximately equally represented. Most adolescents were born in the Netherlands (97.5%). All participants attended regular secondary education and were in their first (i.e., US Grade 7; n = 460) or second year (i.e., US Grade 8; n = 207) (Mage = 12.9 years; SDage = 0.7; age range = 10.1 to 14.9) at wave 1 and wave 2. More than half of the participants (57.6%) were in pre-university education, 8.2% of the participants was in higher general secondary education, and 34.2% of the participants was in pre-vocational education.
Moreover, 777 mothers or fathers provided consent to participate in the study themselves, of which 593 took part in Wave 1 and 586 took part in wave 2 (98.8% in both waves). Both parents of the adolescents were invited to participate in the project, though only in 85 cases, both caregivers actually participated. In case two caregivers participated, we only included the biological mothers (n = 83; excluded: n = 5 non-biological mothers; n = 80 biological fathers; n = 2 non-biological fathers). Although some fathers participated in the study (N = 148 in first wave, N = 135 in second wave (91.2% in both waves), we chose to only include data of mothers. According to literature mothers are still the most important caregivers in the family, and are more prone to stress and depression [12, 15, 16] than fathers. Also, in the remaining sample in which only one caregiver participated, biological mothers participated most often (n = 352 biological mothers; excluded: n = 1 non-biological mother; n = 68 biological fathers, n = 2 non-identifiable), resulting in 435 biological mothers. We only included cases with data on the main measures on both waves in both mothers and adolescents, leaving a final sample of 336 biological mothers.
Most mothers (97.0%) were born in the Netherlands. Mean age of mothers at the first wave was 44.7 years (SDage = 4.2; age range = 29.8 to 57.3). Most mothers finished higher professional education (39.9%) or secondary vocational education (39.4%) and performed a payed job of less than 32 hours per week (52.5%) or 32 hours per week or more (19.4%).
Procedures
When a secondary school agreed to participate, all adolescents attending the first and second grade and their parents were invited to participate in this study by means of an active parental consent procedure. A letter describing the four-wave study was mailed to the parents and they were asked to return a (paper or online) consent form indicating whether they agreed to their child participating in the study and if they agreed to participate in the study themselves. Children were rewarded with a small incentive, if at least one of their parents’ forms was returned, regardless of whether permission was given. Before participation, adolescents and parents were informed that participation was voluntary, that answers would be processed anonymously, and that they could withdraw from the study at any moment. Inclusion criteria for participants were being enrolled in a high school, being in the first and second grade of this high school, being proficient in the Dutch language and parents and children both having given active informed consent. Exclusion criteria for participants were not being proficient in the Dutch language, attending special education and not having given active (parental) consent.
Adolescents completed an online survey at school during one classroom hour (approximately 45 minutes), and height and weight were measured outside the classroom by trained students. Parents completed an online survey, which took approximately 20 minutes to complete. The questionnaires were administered through Qualtrics Survey Software (Qualtrics, Provo, UT, USA). Children received a small present after completing the survey, and several prizes were raffled among participating parents. The Institutional Review Board of the Faculty of Social Sciences of the Radboud University, Nijmegen, The Netherlands approved the study protocol (reference number ECSW20170805-516) in 2017.
Measures
Depressive symptoms
Maternal depressive symptoms were assessed with the 10-item short version of the Center for Epidemiological Studies-Depression (CES-D) scale. The (shortened) CES-D is widely used and has adequate internal reliability [46]. Respondents rated items on a 4-point Likert scale (rarely or none, to most or all the time). The scale includes positive (I was happy) and negative (I could not get going) items. Higher total CES-D scores reflect greater maternal depressive symptomology. In the current study, Cronbach’s alpha for the CES-D was .77 at T1 and .80 at T2.
General Stress
Maternal general stress levels were assessed using the 4 item Perceived Stress Scale (PSS). The PSS is a self-report questionnaire measuring a person’s evaluation of stressful situations in the previous 1 month of his or her life. It is a global measure of stress that is simple to use, and there are many studies confirming its reliability and validity in a variety of settings and in multiple languages [47–52]. The instrument contains 4 statements which measure how unpredictable and uncontrollable respondents feel their lives are, for example: In the last month, how often have you felt confident about your ability to handle your personal problems? Respondents rate how often they experience stressful situations on a 5-point Likert scale ranging from ‘never’ to ‘very often’. Answers of the 4 items were summed into a total PSS score. The higher the score on the PSS, the greater the respondent perceives that their demands exceed their ability to cope. Cronbach’s alpha was calculated to investigate the internal reliability of the Perceived Stress Scale and was .70 at T1 and .69 at T2.
Financial Stress, Stress At Work And At Home
Three questions concerning perceived stress due to financial strain, perceived stress in the home environment, and perceived stress in the work environment during the past year were asked to measure domain specific maternal stress. Respondents rated how often they experienced stress in different contexts: financially, at home or at work on a 4-point Likert scale (never, sometimes, regularly, all of the time).
Anthropometrics
Adolescents’ height and weight were measured according to protocol [53] by trained research assistants. Body Mass Index (BMI) was calculated as weight in kilograms divided by height in meters squared. Individual age and gender-specific BMI standard deviation scores (z-scores) were calculated using a Dutch representative sample of 0-21-year olds [54]. Mothers reported their own height and weight based on which we calculated maternal BMI.
Covariates
Adolescents’ level of education (1 = lower general secondary education; 2 = higher general secondary education and pre-university education) and gender of adolescent (0 = boys; 1 = girls), and maternal BMI were included as covariates.
Statistical Analyses
Statistical analyses were conducted using the PASW 20.0 and R software package. Descriptive statistics were used (mean, standard deviations and percentages) to describe the study sample and to investigate population characteristics (see Table 2). To assess whether covariates were confounded with the outcome measure zBMI at T2 a one-way ANOVA was used. Data were analysed using multiple linear regression analyses, with adolescents’ zBMI at wave 2 as the outcome measure and adjusting for adolescents’ zBMI at baseline and potentially relevant covariates (i.e., educational level of the adolescent, gender, and maternal BMI).
Table 2
Linear regressions of maternal stress/depressive symptoms at T1 on adolescent zBMI at T2
| Analyses adjusted for baseline zBMI | Analyses adjusted for all covariatesa |
| R2 | B | SE B | β | P value | R2 | B | SE B | β | P value |
Maternal general stress | .32 | .04 | .02 | .10 | .04* | .32 | .06 | .02 | .14 | .01** |
Maternal depressive symptoms | .31 | .01 | .02 | .02 | .65 | .30 | .01 | .02 | .04 | .99 |
Maternal financial stress | .30 | − .01 | .07 | − .01 | .90 | .31 | .01 | .07 | .01 | .92 |
Maternal stress at home | .30 | − .03 | .07 | − .02 | .68 | .31 | − .04 | .08 | − .03 | .59 |
Maternal stress at work | .30 | .01 | .07 | .01 | .83 | .31 | .01 | .07 | .01 | .87 |
** significant at the 0.01 level (2-tailed). * significant at the 0.05 level (2-tailed). aCovariates: Adolescents’ zBMI at baseline, educational level, gender, maternal BMI. |
First, to examine cross-sectional associations between mothers’ wellbeing and adolescent zBMI and the covariates, Pearson's correlation coefficients were calculated. Second, to test whether maternal stress or depressive symptoms may precede the development of child weight over time, multiple linear regression analyses were performed using R software package (R Core Team, 2018). The lavaan package in R was used in order to account for missing values and to deal with potential issues involving the non-normal distributions of the outcome measure and other variables. Separate regressions were performed with depressive symptoms (CES-D score), general stress (PSS score), financial stress, stress at home or stress at work at T1 as the independent variable, and adolescents’ zBMI at T2 as dependent variable. We investigated main effects of maternal depressive symptoms and maternal stress on adolescent’s zBMI at wave 2, after correction for baseline zBMI, and the effects of potential covariates (i.e., educational level, gender, and maternal BMI).