"an association between maternal experience of childhood abuse and risk for ADHD in offspring"

As per the title of this post - "an association between maternal experience of childhood abuse and risk for ADHD [attention-deficit hyperactivity disorder] in offspring" - this is another entry about some uncomfortable but potentially important research [1]. Indeed, the findings reported by Andrea Roberts and colleagues continue a theme from this research group (see here and see here) on how maternal exposure to various forms of abuse both in childhood and adulthood *might* have some important repercussions for offspring psychological and developmental health and well being.

The authors begin with the premise that: "Children whose mothers experienced childhood abuse are more likely to suffer various neurodevelopmental deficits" based on quite a lot of their own previous findings [2]. Such abuse - which comes in many different forms - is, they observe, likely to impact various psychological and biological functions; some of those functions *could* also have an inter-generational effect.

So: "We examined the association of maternal experience of childhood abuse with ADHD in offspring, assessed by maternal report of diagnosis and validated with the ADHD Rating Scale-IV in a subsample, in the Nurses' Health Study II (n = 49,497 mothers, N offspring cases = 7,607, N offspring controls = 102,151)." The Nurses' Health Study II seems to be a favourite resource for these researchers, and continues to contribute to many areas of health science and research (see here). Alongside looking at maternal experience of abuse and ADHD diagnosis in offspring, researchers also looked for the presence of various other 'adverse circumstances' that might be important to any enhanced risk of offspring ADHD being diagnosed. This included exposure to tobacco smoking (see here) which has some pretty strong 'observational' evidence on a possible effect.

Results: "Exposure to abuse was associated with greater prevalence of ADHD in offspring." Although important, the nature of the relationship between abuse exposure and offspring ADHD was not exclusive, i.e. ADHD was present in both offspring of mums exposed to abuse and those not exposed to abuse. The percentage difference between abuse exposure vs. no exposure was statistically significant however, and importantly, remained significant even after adjustment for those other adverse circumstances mentioned previously. Ergo, maternal exposure to childhood abuse *might* have an important impact on offspring enhanced risk of a diagnosis of ADHD.

Although requiring further study, these are important findings. A case is made for further inspection of how such a relationship comes about covering important areas such as the effects of childhood abuse on maternal state and behaviour(s) [3] and indeed, whether adverse pregnancy factors such as tobacco smoking may also actually be related to such previous experiences of abuse [4]. I daresay that things are going to be complicated and not straight-forward when it comes to any relationship(s) and so no sweeping generalisations are required from me or anyone else.

The possibility of an 'inter-generational' aspect to the experience of childhood abuse and subsequent offspring ADHD risk is important. It provides evidence that the expression of some childhood developmental disorders may not necessarily be 'hard-wired' in a genetic sense (assuming that is, that exposure to childhood abuse is not able to 'modify' the structure/functioning of the genome [5] for example). It provides evidence for the idea that adverse life experiences may be able to manifest as physical issues (being careful how I use the term 'biopsychosocial' for example). It also might suggest that alongside the continuously important stress on preventing any form of childhood abuse, there may interventions that could eventually be put in place to 'undo' any biological effects that it causes to offspring... Eventually.

I do want to end by reiterating that whilst the experience of childhood abuse may be *associated* with a heightened risk of offspring ADHD, such a relationship does need to be treated with some caution. I'm particularly keen to 'nip in the bud' any idea that every diagnosis of ADHD is somehow an intergenerational product of abuse: it's not.

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[1] Roberts AL. et al. Association of Maternal Exposure to Childhood Abuse With Elevated Risk for Attention Deficit Hyperactivity Disorder in Offspring. Am J Epidemiol. 2018 May 14.

[2] Roberts AL. et al. Maternal exposure to intimate partner abuse before birth is associated with autism spectrum disorder in offspring. Autism. 2016 Jan;20(1):26-36.

[3] Chronis AM. et al. Maternal depression and early positive parenting predict future conduct problems in young children with attention-deficit/hyperactivity disorder. Dev Psychol. 2007 Jan;43(1):70-82.

[4] Pear VA. et al. The Role of Maternal Adverse Childhood Experiences and Race in Intergenerational High-Risk Smoking Behaviors. Nicotine Tob Res. 2017 May 1;19(5):623-630.

[5] Cecil CA. et al. Epigenetic signatures of childhood abuse and neglect: Implications for psychiatric vulnerability. J Psychiatr Res. 2016 Dec;83:184-194.

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