association between SES and childhood ADHD specifically, with a focus on the role of family life.
A recent study in the UK explored the link between SES and incidence of ADHD. The authors utilised GP records through the Clinical Practice Research Datalink, which holds routine data for around 13.5 million individuals. The authors used the IMD of the GP surgery as their SES measure, and Read codes for ADHD diagnosis and treatments as their outcome. They found that those attending GP surgeries in the most deprived IMD quintile had a
significantly higher incidence rate of ADHD cases than the other four quintiles: 13.84 cases per 10,000. Similarly, those in the least deprived quintile had a significantly lower incidence rate than the other four quintiles (9.24 cases per 10,000) (Hire et al., 2015): a relative risk of ADHD of 1.50 (95% CI 1.38, 1.63) for those in the most deprived quintile compared with the least deprived. In order to establish whether practice-level IMD is a relevant measure of SES for individuals, the authors further reported that individual IMD data were available for 80% of patients with ADHD, and in 70% of instances, patients were either living in areas of equal or higher deprivation than their GP surgery IMD (Hire et al., 2015). This study provides initial evidence that there is indeed an
association between SES and incidence of ADHD in the UK.
A study by Larsson et al. (2013) examined in detail the association between family income in early childhood and ADHD in a cohort of 811,803 children, with low income considered by the authors as a marker of causal factors for ADHD. Utilising data from Swedish national registers, the authors used information from cousins and siblings of children with an ADHD diagnosis (or prescription for stimulants) in order to reduce confounding from genetic and shared environmental effects. They found that those in the lowest income quartile had a hazard ratio of 1.61 for ADHD as compared with the highest quartile, and the rising risk was incremental in line with lowering income quartiles (Larsson et al., 2013). One aspect that is apparent from the study is that many factors that are modelled in the causal pathway have relatively small effects on ADHD as an outcome. The authors found that the impact of low income on ADHD risk was similar in magnitude to that of low birth weight or
preterm birth: both universally acknowledged to be robust predictors of poor health throughout life (Hack, Klein and Taylor, 1995).
In line with the above, an earlier study examined the impact of low income and child health (measured by mother reports of physical symptoms and child’s general health status), and found that this association in the Avon Longitudinal Study of Parents and Children (ALSPAC)is almost completely eliminated when taking into account maternal behaviour and mental health (Burgess, Propper and Rigg, 2004). The authors also examined the timings and duration of these impacts, and found that persistent low income seems to be more detrimental for child outcomes than being of low income at one time point in the study. These findings drive the conversation back to the potential of there being a direct impact of low income on the aetiology of ADHD, and whether material resources are of crucial importance in this (Burgess, Propper and Rigg, 2004). From the above evidence it could be considered that this may be
because of the lack of resources to provide a stimulating environment for the child during early development.
I have briefly mentioned that the impact of parental ADHD (and thus low SES) on a child’s outcome of ADHD may be due to genetic selection. The impact of a parent having ADHD may however exert effects on the child’s outcome in other ways. One Canadian study explored parenting behaviour in a sample recruited from the local community of 80 mothers with differing levels of ADHD symptoms. Those mothers with higher levels of ADHD symptoms
reported having lower parenting self-esteem than the low ADHD symptom group, as well as reporting lax parenting and using more ineffective disciplinary styles (Banks et al., 2008). ADHD symptoms were also related to comorbid disorders: this is not surprising as a high percentage of children with ADHD will also have other mental health disorders such as conduct disorder (CD) or anxiety (Banks et al., 2008). Of these comorbidities, the authors found no link between ADHD and co-existing depression in their sample of mothers, which is of interest as I have discussed parent mental health as a potential causal process and findings have been reported linking maternal mental health and child ADHD. However this may be because a convenience, non-clinical sample was used by Banks et al., and as there is a low base-rate of problems in these samples, a much larger sample of mothers would be needed to detect whether ADHD and depression do co-occur.
Also exploring parenting and ADHD, Harvey et al. (2003) recruited a sample of parents with ADHD whose children were also diagnosed with ADHD, and examined different aspects of parenting. The authors found that mothers who reported inattentive symptoms were more likely to report lax parenting and also negative parent-child interactions (the latter especially if the mother
reported moderate levels of inattentive symptoms). For fathers, lax parenting was associated with inattention and impulsivity, and arguing during the parent- child interaction may be a risk factor for impulsive symptoms. During the course of the study a parent training programme was conducted: the authors found that after parent training the impulsivity-arguing association in fathers decreased, however the parent training had little effect on parent ADHD symptoms or the quality of the parent-child interactions. The authors also discussed the role that comorbid disorders may play in parental ADHD and the impacts these may have on parenting skills (Harvey et al., 2003).
Furthering the discussion on parental ADHD when the child also has ADHD symptoms, Psychogiou et al. (2008) take a different perspective from that considered above. The authors discuss the negative effects of child ADHD on parenting, acknowledging that parents who have a child with ADHD find their child’s behaviour to be both stressful and challenging, which leads to negative impacts on parenting. This cycle between parent and child influence on
parenting strategies is teased apart by the authors when exploring whether the mothers’ own ADHD symptoms may result in different parenting skills. They found that parenting of children with high levels of ADHD symptoms was more critical, directive, negative and less socially engaged than parenting of children with low ADHD symptoms. However when the mother and child both had high levels of ADHD symptoms, parental responses to the child were more positive and affectionate than when the mother did not also have ADHD symptoms. The authors also found that the negative impacts of child ADHD symptoms on parenting were much lower when mothers had high levels of ADHD symptoms, because of higher levels of positive parenting (rather than less negative
parenting) (Psychogiou et al., 2008).
Whilst Psychogiou et al. (2008) consider ADHD in mothers of children with ADHD, Romirowsky and Chronis-Tuscano (2013) consider the role of fathers’ ADHD symptoms on conduct problems in children with ADHD. The authors found a differential effect due to involvement: if a father had low
involvement in parenting, his ADHD symptoms were not related to child conduct problems. However, if the father reported being highly involved with parenting then his ADHD symptoms were positively related to the child’s conduct
problems. Also of interest was the interaction found with SES: low SES fathers were less likely to be highly involved with parenting than high SES fathers. The authors concluded that paternal involvement moderates the relationship
between paternal ADHD symptoms and conduct problems in the child with ADHD. This study highlights the complex interaction between how a parent’s own ADHD symptoms may relate to a child with ADHD; pathways include genetic effects, effects of parenting involvement, susceptibility to other mental health problems and parenting skills. It has also been discussed how across all of these factors the impact of low SES on a family increases the chances of negative outcomes for all involved (Romirowsky and Chronis-Tuscano, 2013).
2.4 ADHD and SES within an ecological framework