Results showed that neighbourhood factors did not predict changes in general health or mental health in the period of transition from late childhood to early adolescence. However, NSD was associated with a positive change in self-esteem and satisfaction in adolescents from lower educated parents, while it predicted a negative change in adolescents from higher educated parents.
The baseline measurement of the present study did show associations between neighbourhood factors and general and mental health [3], and a Chicago cohort study in children aged 5–11 year, using a 2-year follow-up period, also showed associations with mental health [22]. Therefore, any effect of the neighbourhood may be restricted to children aged 11 years or younger. Informal social control may prevent mental health problems in primary school children only, because older children spent more time outside the neighbourhood, for example in the neighbourhood of their school. This is also in agreement with a study in older adolescents and young adults (15–25 years) that did not find evidence for an association in Mexico [29]. An U.S. experimental study including children between 8 and 18 years old (Moving to Opportunity: MTO) showed that children that were randomly assigned to receive vouchers to move to a non-poor neighbourhood had higher levels of mental health; again greatest effects were found in the younger children, possibly because older children can travel back to their old neighbourhood [17].
However, in the present study, levels of self-esteem and satisfaction increased when family socioeconomic status and NSD concurred. This indicates that the neighbourhood also impacts on 13/14 year-olds. In a previous study, minority children living in a dissonant environment were reported to have lower levels of self-esteem than minority children from segregated but protected environments [30]. The current results suggest this type of contextual interaction may apply not only to ethnic group status, but also to socioeconomic status itself.
The increased self-esteem of adolescents from lower educated families in poor neighbourhoods may indicate the mediating effects of peer influence on self-reported quality of life. Much of the emphasis in social capital-related research concerning the transition from childhood to adolescence has been on the family and school social control processes as well as neighbourhood factors. However, it has also been recognized that peer influences in life course transitions cannot be ignored and the suggestion has been made that peer attachments may have a neutralizing influence on the informal social bonds formed in family and school [31]. Youth in poor neighbourhoods with relatively weaker school and family social bonds may be likely to associate with specific peer groups of adolescents with similar family backgrounds as has been suggested in the literature on selection and assortative pairing in adolescent behaviour [32, 33]. To our knowledge, the present article is among the first that reports these specific statistical associations between neighbourhood deficit factors and positive psychological well-being factors in youth. These findings will have to be replicated in future studies. The hypothesis that needs to be investigated is that under the specific conditions of persistent poverty and lower levels of parental education, disadvantaged youth may be more likely to pair with others in youth peer groups that have compensatory functions for deficits in the neighbourhood, schools and at home. Under these concentrated disadvantaged conditions where low self-esteem might well be expected, the youth peer group intervenes to provide a countervailing force producing a strong identity and with it an unexpected heightened sense of self-esteem. This process has been extensively documented in studies of youth gangs that are especially prevalent in urban areas characterized by concentrated disadvantage, migration and residential instability [34–36]. Although similar gangs do not exist in a small European city, like Maastricht, current results suggest that psychological outcome and socioeconomic conditions are similar in Maastricht.
Furthermore, both the positive association in adolescents of lower educated parents and the negative association in adolescents of higher educated parents between NSD and self-esteem appeared stronger in neighbourhoods low in social cohesion and trust. Thus, strong cohesion and trust mitigated effects of non-concurring family socioeconomic status and NSD. This is in line with a previous study, showing a stronger association between NSD and children's mental health service use in neighbourhoods low in social cohesion and trust [6]. This previous study concluded that neighbour interplay reduced the association between neighbourhood poverty and mental health, therewith stressing the beneficial effects of social capital. This NSD * social cohesion and trust interaction found in the present paper also indicates that the associations between cohesion and self-esteem are strongest in affluent neighbourhoods, in particular in children of lower educated parents. Thus, although children of lower educated parents tend to do worse in these areas, social cohesion and trust seems to reduce deterioration of self-esteem. On the other hand, this association was weaker in poor neighbourhoods and not statistically significant. This is in agreement with a previous study reporting that "sense of community" is positively associated with behavioural problems in affluent, but not in poor neighbourhoods [5]. However, the conclusion that social capital is only beneficial in affluent neighbourhoods is not warranted because social cohesion and trust also mitigated the effects of neighbourhood poverty both in the present and in a previous study [6].
Methodological issues
Social capital is an umbrella term including many different constructs [37]. Only two of these constructs were included in the present study (informal social control; social cohesion and trust). These two scales were selected because these were the best validated measures at the time and the scales were used in a large cohort study in Chicago, with a very similar design, so that we could compare effects [38]. It is possible that analysing other constructs would yield different results. These previous analyses also showed that in Maastricht, ethnicity is not associated with quality of life outcomes [38]. Therefore, ethnicity was not included as a confounder in the present analyses. Because the Maastricht population is predominantly white, it may not be possible to extrapolate findings to larger and ethnically more diverse cities. However, for European small cities and towns like Maastricht, that typically have a low proportion of non-Western immigrants [39], the results may provide a public health perspective. In addition, a study in a relatively homogeneous population avoids difficulties of studying ethnically heterogeneous populations, such as language problems and cultural differences. More research in ethnic minority groups and ethically diverse populations can give more insight in the external validity of the present findings. Results regarding self-esteem and satisfaction may be stronger in ethnically more diverse populations because minority children living in a dissonant environment were reported to have lower levels of self-esteem than minority children from segregated but protected environments [30] (see above).
The strength of the present study is its longitudinal design that enables the prospective investigation of changes in quality of life in the transition to early adolescence. Furthermore, a principle objective of our methodology was to examine effects of neighbourhood variables that were obtained independently of the responding adolescents. Because perceptions of social capital are always biased by individual mental health status, it is difficult to disentangle cause and effect. The purpose of studying more distal mechanisms constituting objective social capital was realized by measuring social capital scale items in a group of informants that was different than the cohort investigated [40]. However, although both ISC and SC&T were measured independently of the study sample, answers of all informants are coloured by their individual characteristics [41]. On the other hand, individual socioeconomic and demographic composition provide the basis for social interactions in a neighbourhood and, therefore, controlling for individual characteristics leads to over adjustment [41].
The present paper has some limitations. First, in a longitudinal study there is always loss to follow-up. Although 79% of the baseline responders also responded at follow-up, which is relatively high, parental educational status differed between those who dropped out after baseline and those who responded to the follow-up questionnaire (t-test, p = 0.01). However, it is unlikely that this impacted on the results, as results (table 3 and 4) were stratified by parental educational status because of interaction between individual and neighbourhood socioeconomic status. This selective non-response could have led to a decreased power in the stratum of adolescents with low parental education, but table 3 shows greatest effects in this group.
Second, the response rate in the social capital community survey in adults was only 48% [3]. However, the community sample respondents and the general population between 20 and 65 years of age do have similar distributions in age, gender and ethnicity. Furthermore, all respondents were considered to be "key" informants about their own neighbourhood, with the implicit assumption that responders gave the same information about the neighbourhood as the non-responders would have given. The validity of the sample might have been judged differently if the principle objective was to obtain information on the person, not his or her neighbourhood. Thus, this information is more or less independent of the response rate. In order to verify this assumption, we examined post hoc associations between ISC and SC&T collected in the family cohort (parents), and those collected in the community survey (reproducibility). Neighbourhood scores on ISC and SC&T based on these questionnaires were highly correlated.
Inclusion of educational status and occupational status guarantees satisfactory control for individual level socioeconomic status in the Netherlands [42]. However, the possibility remains that residual confounding may have lead to spurious results at the neighbourhood level, because of omitted variable biases [1]. Families moving into poor or not moving out of poor neighbourhoods may differ from their peers although equally poor or affluent (e.g. in motivation, literacy etc). Smoking and obesity are factors that are associated with neighbourhood of residence and can hypothetically influence health outcomes [43–45]. Because at baseline none of the adolescents smoked, post hoc we repeated the analyses including obesity only as an extra confounder. Results were very similar, but effects in self-esteem in the middle stratum of parental education were somewhat stronger and statistically significant. In addition, although physical activity may be associated with health and quality of life outcomes, this measure was not included in the present study. Physical activity may be more easily obtainable or attractive in advantaged neighbourhoods, because of the neighbourhood environment or the presence of better equipped facilities. Given the fact that adolescents' quality of life in advantaged neighbourhoods as a result of more and better sports facilities, controlling for physical activity would result in smaller effects. Therefore, it is highly unlikely that physical activity is the reason that we did not find an effect of neighbourhood variables on quality of life. On the other hand, the problem of unhealthy reductions in physical activity tends to increase only in late adolescence [46], while our study ended in young adolescence. In addition, it is not likely that it impacts our main finding: the interaction between individual socioeconomic status and neighbourhood socioeconomic disadvantage.
Furthermore, none of the models showed statistically significant variance at the neighbourhood level (σμ
2), and intra class correlations (ρ) were low. Theoretically, variance at each level warrants including that level in the analyses [28]. However, neighbourhood researchers tend to analyse neighbourhood effects, even when intra class correlations and neighbourhood variation are low, and it is generally held that this is warranted [47]. In addition, in line with low neighbourhood-level variance, results showed no main effects of any of the neighbourhood variables. This does not rule out hypothesized interaction effects: neighbourhood-level variables were associated with outcomes in subgroups of adolescents.
The main outcomes of our study were quality of life and mental health and, therefore, the CHQ was included in the research instruments. CHQ-subscales are all continuous variables. Some prefer the use of dichotomous health outcomes. However, dichotomization results in loss of information and was not necessary here. This could reduce the comparability of the results to studies that did use dichotomous outcomes, but in neighbourhood research both dichotomous and continuous outcomes have been studied. Although the CHQ is a comprehensive instrument, the number of items per psychological domain is relatively low compared to psychological questionnaires like the CBCL. Therefore, the questionnaire is suited for research in the general population. However, in order to enable studies to address multiple research questions after a single data collection, one may prefer to further reduce the number of items. For general health, there is a widely-used and validated one-item alternative: "How do you perceive your health?" (answers on a 5-item Likert type scale: 1 excellent, 2 very good, 3 good, 4 fair, or 5 poor) [38]. This question (in Dutch) as well as one question on psychological problems (yes/no) are included in a new Maastricht data collection. Both concurrent (e.g. with the strengths and difficulties questionnaire, SDQ) and predictive validity will be studied in the future, using, amongst others, matching procedures with the psychiatric case register that records psychiatric service consumption. More research is needed to find and validate one-item alternatives for the self-esteem and satisfaction questions.
Associations between NSD, informal social control, and social cohesion and trust were so strong that collinearity problems would likely have arisen had these three variables been entered jointly in one regression model. Therefore, all neighbourhood variables were entered in the models separately, except when analysing interaction effects between two neighbourhood variables.
Finally, a previous study in another Dutch city on changes in behavioural problems between the age of 11 and 13 years, showed a statistically significant association between NSD and only one of the six behaviour outcomes [4]. Because all changes in behaviour were in the expected direction, the authors proposed that a longer follow-up period could reveal statistically significant changes. Future data collections with longer follow up periods may reveal more associations between neighbourhood factors and changes in general and mental health, and associations with self-esteem and satisfaction (in subgroups) could be replicated.
