in 1980 with the Black Report, where the gap in both income and health
outcomes between the wealthy and the poor was highlighted (Black et al., 1980). Since then, a large body of literature has examined how parental
socioeconomic status can impact on a child’s health outcomes, both of physical and mental health (Bradley and Corwyn, 2002, Najman et al., 2004, Reiss, 2013, Schneiders et al., 2003). Indeed, although research has traditionally considered SES to be a distal factor in that it impacts on child health indirectly, recently an argument has been put forward to consider SES a proximal
determinant of health (Kelly, Kelly and Russo, 2014).
SES and mental health in children
Reiss (2013) conducted a systematic review exploring the association between socioeconomic inequalities and mental health outcomes in children and adolescents. In the review Reiss explores theories of social selection (“assumes that people with mental health problems drift down in socioeconomic position because of their psychopathology and inability to fulfill expected role obligations”) and social causation (“posits that mental health problems are a result of socioeconomic deprivation”), with the caveat that the two theories are
not mutually exclusive (Reiss, 2013). Of the 55 studies she included, 52 had results indicating an inverse relationship between SES and mental health, concluding that those of low SES are two to three times more likely to develop mental health problems in childhood or adolescence than their higher SES peers. The review has many strengths; a comprehensive search included research from 23 countries with a mixture of cross-sectional and
longitudinal/cohort designs. The author also includes many measures of SES in the review, and indeed identifies the need for clearly defined definitions of SES due to the heterogeneity of measures and concepts included in the reviewed studies. Reiss found that the SES measures most associated with poor mental health outcomes were parental income and education, as opposed to
occupation or employment status.
Reiss (2013) describes the relationship between mental health problems and SES as a cycle that operates across generations. The obvious flaw with applying the social selection hypothesis to cases of child mental illness is that it is parental SES which is associated with this, and children are rarely able to influence their socioeconomic position themselves, except in exceptional circumstances such as children who became famous and wealthy after
successful acting roles. Reiss (2013) highlights how social selection may work in the case of ADHD: assuming the parent has genetic traits for ADHD
themselves they may then experience downward social mobility because of their ADHD, and these traits are transmitted to the child who is subsequently diagnosed with ADHD.
Hudson (2005) also explored theories of social selection and social causation with regards to mental illness by examining both census data and data for acute psychiatric hospitalisation of 109,437 individuals over a six year period. Hudson found that social causation theory was more strongly supported by the data than social selection as they found no evidence of downward drift in SES of hospitalised individuals, yet they did find an association between low SES and mental illness. This research in adults supports theories of social causation, yet the relationship across generations is in need of clarification.
SES and child emotional and cognitive development
Najman et al. (2004) explored the intergenerational transmission of socioeconomic inequalities using emotional health and cognitive development
of children as their outcome, due to the strong links between these domains in childhood and health-related behaviours in adulthood. The authors suggest that being born to parents of low SES means that a child begins life with a “poorer platform of health” and has less capability than their peers to benefit from potential advances in economic and social resources. Najman et al. (2004) followed up a cohort of 8,556 pregnant women until their child was age 14 (n= ~4,600). The authors not only looked at parental SES but also that of the
maternal grandfather. They found that externalising problems in the child at age 14 were associated with their having a teenage mother, being in a low income family, living in a single parent household and also having a grandfather who was in the lowest SES group based on their occupation. Internalising problems were associated with having a younger mother and being in a low income family. The authors conclude that some health inequalities may be transmitted across generations. Unfortunately the authors did not examine the impact of change in SES of the family on child outcomes, which may have further informed the debate.
SES and resilience in child development
Having established links between socioeconomic disadvantage and behavioural problems in childhood, both internalising and externalising, Flouri, Midouhas and Joshi (2014) examined factors that predicted resilience to emotional and behavioural problems in children from families of low SES. The authors theorise that the pathway between parental low SES and child
internalising and externalising problems is due to the increased stress on the parents because of lack of social and economic resources, which may lead to poor parent mental health. Poor mental health may then increase the likelihood of poor parenting practices and so increase the risk of the development of emotional and behavioural problems in the child. The concept of resilience is of importance because it is known that not every disadvantaged child goes on to experience mental health problems, and as such there must be individual differences in resilience as well as risk factors.
Flouri, Midouhas and Joshi (2014) investigated interacting characteristics that influence resilience. The authors found that high self-regulation abilities in the child in a sample of 16,916 families acted as a protective factor by
moderating the relationship between low SES and emotional and behavioural 43
problems. Children of low SES who had high self-regulation abilities were less likely to develop emotional/behavioural problems than their peers of middle SES with poor self-regulating abilities. The authors suggest that both high self-
regulation and good verbal cognitive abilities were protective factors in the study, but highlight the role of parents in mediating these effects. It may be that the detrimental effects of SES are lesser in magnitude than positive effects of child resilience, especially with regard to self-regulation.
In the case of ADHD, one of the prominent aetiological theories is that there are deficits in the child’s ability to self-regulate their responses and behaviours. If this is indeed the case, children with ADHD are highly unlikely to have high self-regulation abilities, thus limiting the potential protective power of this trait. In the sample used by Flouri, Midouhas and Joshi (2014), the
Millennium Cohort Study (MCS), it would have been of interest to know if any of the children with high self-regulation abilities were diagnosed with ADHD or had attention problems. This illustrates that mechanisms between SES and ADHD are likely to be complex and involve both risk and protective factors. If children from low SES households are more likely to have poor self-regulation abilities, this ADHD-related trait potentially exposes them to an increased risk of ADHD through lack of resilience. Circular risks and exposure relationships like this illustrate how complex the relationship between SES and ADHD is likely to be: more studies focussing on specific characteristics of the SES-ADHD
relationship are needed.
Mechanisms of links between SES and child development: parental well-being
Utilising the MCS, Kiernan and Mensah (2009) found that 18% of the children in persistently poor families had behavioural problems as compared with 4% of children in non-poor families. Children of poor families were also more likely to have cognitive delay. The authors also investigated maternal depression as a putative mechanism that may explain the findings and found that it was associated with behavioural problems in three year old children, in fact they found that maternal depression was a stronger predictor for
behavioural problems than poverty (defined as an income of 60% below the median before housing costs were taken into account), and poverty was a stronger predictor for cognitive delay. This study lends support for the
theoretical mechanism proposed by Flouri, Midouhas and Joshi (2014), and with regards to ADHD this could mean that children who are in a
socioeconomically disadvantaged family where the mother has experienced mental health problems could be particularly at risk for ADHD. Alternately, SES may be a confounder in the relationship between maternal and child mental health problems.
Boe et al. (2013) also examine the role of emotional well-being of parents and parenting practices in the association between SES and child mental
health. The authors explore Conger and Elder’s Family Process Model (Conger and Elder, 1994), which puts forward the theory that parenting is a key
mechanism through which the SES-child wellbeing relationship operates. There is supporting evidence for this mechanism described above, and the association has been established using measures of income for SES (Benner and Kim, 2010, Parke et al., 2004, Mistry et al., 2002). Boe et al. (2013) expand on this by using multiple measures of SES, in particular maternal education, as it has been suggested that mothers of higher educational level will have more knowledge about child rearing and thus have more supportive parenting
strategies than lesser educated mothers (Morawska, Winter and Sanders, 2009, Waylen and Stewart-Brown, 2010). The authors hypothesise that because of this education may have a direct effect on child mental health and income an indirect effect through parental well-being. This hypothesis was supported by their analysis. Additionally, the authors found that the effect of maternal education operated through negative discipline (factors related to child punishment). This however may be an oversimplified conclusion, as paternal education was found to be associated with child externalising problems but not mediated by any measured parenting factor (Boe et al., 2013).
The above studies examine parent mental health and well-being mainly in a cross-sectional manner or during the lifetime of the study child. Van Batenburg-Eddes et al. (2013) bring consideration of timing to the forefront in their examination of parental depression and anxiety during pregnancy and attention problems in children at age three or four. Although the authors found an association between maternal symptoms of anxiety or depression in
pregnancy and subsequent attention problems, they found that this was no longer significant when they adjusted for mental health problems after birth. They also found similar associations between maternal and paternal mental
health problems during pregnancy, suggesting that intrauterine effects are not the cause of this association (Batenburg-Eddes et al., 2013). If the timing of exposure to parental mental health problems during pregnancy is not key to the development of ADHD, research that investigates exposures during childhood is well positioned to further explore these mechanisms.
Mechanisms of links between SES and child development: home learning environment
Mulligan et al. (2013) explored the home environment in terms of enrichment, learning materials and opportunities, family factors, physical environment quality and other dimensions, and found that children under the age of ten who had a poor quality home environment or fewer opportunities for learning at home were rated as having more hyperactive and inattentive
symptoms by their teachers. SES was measured in this study as the type of occupation held by the parent and was found to have a relatively low
contribution to ADHD symptoms. This may reflect the choice of SES measure. Schmiedeler, Niklas and Schneider (2013) also examined the home environment with regard to development of ADHD, with their definition and measure of home environment encompassing the provision of intellectual stimulation for the child, measured by parent report of what was present in the home and what activities parents engaged in with their child (e.g. reading
books). The authors also considered family SES, and hypothesise that because parents of higher SES are more likely to engage in development-enhancing activities with their children than their lower SES counterparts, the link between low SES and ADHD could be explained by these parenting practices. They found that both low SES and poor home learning environment were associated with increased symptoms of ADHD in a sample of 924 children (although the SES-ADHD association was not statistically significant at p<0.05), and that home learning environment mediated the association between SES and ADHD (which was statistically significant at p<0.05). The authors used a measure of occupational prestige for SES and utilised a community sample (Schmiedeler, Niklas and Schneider, 2013).
2.3 Research exploring associations between SES and ADHD