Saturday, 17 November 2018

"Children are getting weaker, study finds"

The title of this post - "Children are getting weaker, study finds" - comes from one of the media headlines covering the study findings presented by Gavin Sandercock & Daniel Cohen [1]. In their study, the authors detail results derived from the Chelmsford Children's Fitness and Activity Survey, an initiative that has been monitoring the fitness of local children (local to Chelmsford) for about 20 years. Their results for the most recent cohort (2014) compared with previous study cohorts (2008, 1998) make for worrying reading: children are getting weaker alongside "a decrease in self-reported physical activity concurrent with the accelerated declines in fitness from 2008 to 2014."

So: "We measured; height, weight, standing broad-jump, handgrip, sit-ups and bent-arm hang in 10-year-old boys and girls from Chelmsford, England in: 2014 (n = 306), 2008 (n = 304) and 1998 (n = 310)." Researchers also asked about recent physical activity among their cohort using the Physical Activity Questionnaire for Children/Adolescents (PAQ-C), a self-report questionnaire. The collected results were analysed and among other analyses, authors "compared percentage change per year 1998–2008 with 2008–2014" across the variables being studied.

As per the headline, the results were worrying: "Pairwise comparisons showed muscular fitness of both sexes was significantly lower in 2014 than in 1998." They also observed that self-reported physical activity was lower in the later cohort. Obviously, I need to stress that this was self-reported physical activity information, so not exactly objective actigraphic data for example. Out of the several results reported relating to specific aspects of fitness across the cohorts, the issue of handgrip strength stuck out for me in light of some still emerging research suggesting that handgrip strength might have "prognostic value for mortality" according to some studies. Without wishing to make connection when none might exist, I do wonder whether such data might one day eventually tally with some other quite worrying statistics on longevity recently published?

Another detail discussed by Sandercock & Cohen is their finding that "Ten-year-olds in 2014 were taller and heavier than in 2008 and 1998 but there were no differences in BMI [body mass index]." They authors talk about this more in their media interviews: "As today's ten-year-olds are taller and heavier than the children measured six and 16 years ago we expect them to be stronger and more powerful, but this was not the case." Worrying. And it also appears that the declines in strength were increasing more rapidly in the later cohort than compared with the earlier ones, as the authors mention that from 1998 to 2008, strength (group strength) fell by just over half a percent per year, whereas from 2008 to 2014 this decline increased to 1.6% per year.

So what does this all mean for the health and well being of the next generation, and what can be done to reverse such trends? Well, health in childhood is often a good indicator of what health will look like in adulthood. I say this not only from a physiological point of view but also bearing in mind that habits bred in childhood tend to persist into adulthood. Low levels of physical activity probably also follow that pattern.

The possible reasons to account for the cohort disparities? Minus any sweeping generalisations I don't think it would be out of place to mention that things have changed quite a bit when it comes to hobbies and pastimes for at least some parts of the paediatric population. More time spent playing video games or on the Internet have perhaps replaced previous scenarios when kids would meet (in person), play out, run around, climb trees, play football and the like. I don't say that to demonise such digital pastimes (see here) but rather to point out a shifting pattern in activities that also have been noted in other relevant studies [2]. It's perhaps also worthwhile pointing out that opportunities for physical activity have also perhaps changed as a function of the environment we now live in. Why else would schools have had to implement strategies such as the daily mile for example?

Possible solutions? When I first tweeted about the publication of the Sandercock & Cohen article I added in the idea that physical activity specifically along the lines of strength and conditioning could perhaps be added to the learning curriculum. So, alongside maths and English (here in Blighty), there is also a focus on physical education too. Yes, I know physical ed(ucation) is part of the school agenda, but I actually meant something like getting kids into a gym and doing something akin to circuit training at least a few times a week. I know this is ambitious and I know that not every kid is going to be able to do this. But surely in these days of adaption and flexibility in teaching and learning, there are also ways to make such exercise open to all. And you never know, start children young with the mindset that exercise is fun and good for physical (and mental) health, and it might just serve them for a lifetime...

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[1] Sandercock GRH. & Cohen DD. Temporal trends in muscular fitness of English 10-year-olds 1998–2014: An allometric approach. Journal of Science and Medicine in Sport. 2018. Aug 1.

[2] Walsh JJ. et al. Associations between 24 hour movement behaviours and global cognition in US children: a cross-sectional observational study. The Lancet Child & Adolescent Health. 2018. Set 26.

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Friday, 16 November 2018

"Children with DDs [developmental disabilities] had higher chronic school absenteeism"

The findings reported by Lindsey Black & Benjamin Zablotsky [1] were not unexpected. Utilising data derived from the 2014–2016 National Health Interview Survey (NHIS) based in the United States, researchers concluded that: "In this nationally representative sample of children aged 5–17 years, children with ADHD [attention-deficit hyperactivity disorder], autism spectrum disorder, and intellectual disability were more likely to have had chronic school absenteeism compared with children who did not have these conditions even after controlling for demographic and selected physical health conditions." The reason I say that such findings were not unexpected is because such observations add to other independent literature on this topic (see here) suggesting that school isn't always a great environment for children with such diagnoses and attendance figures perhaps reflect that.

This isn't the first time that the NHIS has cropped up on this blog (see here and see here). On those previous occasions, the NHIS has provided important evidence that the rates of various developmental disabilities are continuing to increase (autism, developmental delay) whilst some diagnoses are a little more static (intellectual disability) in line with other data (see here). This time around, researchers looked at what role developmental disabilities (DDs) might play in the finding that "14% of all public school students are chronically absent from school, missing 15 or more days per year" in the United States.

Based on the NHIS methodology that involved sampling households with said households completing "a brief questionnaire to collect selected demographics and broad health measures", researchers first ascertained whether "the parent had ever been told by a doctor or health professional
that the child had attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder, intellectual disability, or other developmental delay." They also asked about school absenteeism using the question: "During the past 12 months, about how many days did (sample child) miss school because of illness or injury?" Findings were collated and analysed.

Results: covering nearly 27,000 children, of which about 1 in 10 were diagnosed with ADHD and 2.5% reported to be diagnosed with an autism spectrum disorder (ASD), a few important results emerged. Those diagnosed with an intellectual disability (sometimes called a learning disability here in Blighty) "had the highest prevalence of chronic school absenteeism (14.0%)." Chronic school absenteeism by the way, was defined as 15 or more days missing from school throughout the school year. The percentage rates for school absenteeism for autism, developmental delay and ADHD were 9%, 7.2% and 5.2% respectively. Compared against data from children without any reported developmental disability diagnosis, those with DDs were quite a bit more likely to be chronically missing from school even when adjusted for various other co-occurring physical health conditions such as "asthma, allergies, and headaches" or for other demographic differences ("age, sex, race and ethnicity, poverty status, family structure (categorized as two parent, single parent, or other), and geographical region of residence").

Even taking into account possible research caveats such as the fact that "data are based on a parent or guardian report" the Black/Zablotsky findings represent some important data. 'Every school day counts' is an oft-heard about phrase in educational circles, drawing attention to the idea that not only is educational attendance a legal requirement in many countries, but also that as chronic absenteeism creeps in, so educational chances and opportunities start to slip by and where this can potentially lead (see here). This is bad for the kids, bad for the teachers (who often have to 'go over' missed work) and not particularly great for the rest of the class either.

Bearing in mind all that, the next question should really be 'why?' Why are children with DDs more prone to school absenteeism and what can be done to remedy the situation? Well I don't doubt that it's going to be complicated and so doesn't need any sweeping generalisations from me or anyone else. I'm first drawn to mention that whilst Black & Zablotsky controlled for various physical health conditions that might affect school attendance, they probably did not control for all of them (including bouts of illness due to infections for example) and so one needs to look more closely to see if these exerted any effect on their results (see here for another example). My second preference for further study would be to see whether education is actually meeting the child's individual requirements as another area associated with chronic absenteeism. Y'know, the idea that school can be a source of significant stress and strain for children (see here); even in those educational environments that have a more specialised ethos (see here). Finally, and again minus any sweeping generalisations, more research is needed on family circumstances and child's school absenteeism. I know it's a little uncomfortable to mention but irrespective of a child's diagnostic status or not, some parents are not always 'on message' when it comes to the 'every school day counts' idea. Coupled with a child who might not be particularly interested in school, and well, it's not difficult to see how this could play out with regards to the onset and perpetuation of chronic absenteeism. I would add that this is not a universal 'blame the parents' observation.

There are no easy fixes to this issue. But identifying potentially vulnerable groups, asking appropriate questions and providing targeted support, would seem to me to be a step in the right direction.

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[1] Black LI. &  Zablotsky B. Chronic School Absenteeism Among Children With Selected Developmental Disabilities: National Health Interview Survey, 2014–2016. National Health Statistics Reports. 2018; 118.

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Thursday, 15 November 2018

Big data does... the extreme male brain theory of autism and the Empathizing–Systemizing theory

"Two long-standing psychological theories – the empathising-systemising theory of sex differences and the extreme male brain theory of autism – have been confirmed by our new study, the largest of its kind to date."

That was the opening sentence to a write-up (see here) of a recent research paper published by David Greenberg and colleagues [1] which sought to "test 10 predictions from the Empathizing–Systemizing (E-S) theory of sex differences and the Extreme Male Brain (EMB) theory of autism." The 'big data' words included in the title of this post refer to the collection of data from hundreds of thousands of people as part of a TV documentary that aired here in Blighty called 'Are you autistic?' whose data were included for study. This follows a similar format from some of the co-authors on the Greenberg paper on previous research occasions (see here).

Minus any charges of plagiarism, a few descriptors might be useful. First: "The first theory, known as the empathising-systemising theory of typical sex differences, posits that, on average, females will score higher on tests of empathy than males, and that, on average, males will score higher on tests of systemising than females." Second: "The second theory, known as the extreme male brain theory of autism, extends the empathising-systemising theory. It posits that autistic people will, on average, show a shift towards “masculinised” scores on measures of empathy and systemising." Researchers also talked about something called a 'd score': "the difference between each person’s score on the systemising and empathy tests" in their research, alongside mention of the words 'brain type'.

As part of the interactivity of that TV documentary, some 670,000 people "who indicated they were males or females" completed various measures: "the Autism Spectrum Quotient-10 (AQ-10)... the Empathy Quotient (EQ)..., Systemizing Quotient-Revised (SQ-R)..., and the Sensory Perception Quotient (SPQ)" via an on-line questionnaire portal. About 36,000 people who took part "indicated that they had been diagnosed with an “Autism Spectrum Condition”." Data from responses to the questionnaires were crunched pertinent to those 10 predictions from both theories (said predictions concerned sex differences based on responses to the questionnaires, those various 'brain types' and how responses might look with reference to the presentation of autistic traits). For good measure, researchers also describe carrying out an 'independent replication' of their findings on a separate cohort of adults ("14,354 participants (226 autistic individuals, and 14,119 controls)"). Although there were some minor differences from the larger main trial, to all intents and purposes the same procedures were employed "for calculating brain types and performing statistical analysis."

Results: well "all 10 predictions from the E-S and EMB theories" were confirmed. So for example, men taking part in the study "had a shift towards a high d score" suggestive of being more likely to be systemisers than empathisers, whilst "typical females had a shift towards a low d score" (i.e. more likely to empathetic than systemiser). The previous STEM (science, technology, engineering, and mathematics) findings [2] were also supported, in that: "STEM professionals on average scored significantly higher on the AQ" suggesting a link between the choice of STEM career and autistic traits. And for those reporting a diagnosis of autism or autism spectrum disorder (ASD): "autistic people, regardless of their sex, had a shift towards an even higher d score than typical males" (systemisers) but "were not more likely to work in STEM occupations, compared with controls."

There is a lot to take in from the Greenberg research and related commentary. The study has a number of things going for it insofar as the huge participant size and the use of an independent replication set to confirm findings. These factors should not be underestimated. The limitations? Well, self-report is still one of them, and the fact that at least one of the questionnaires used is probably picking up a lot more than just 'autistic traits' (see here). I'm also inclined to point out once again that the *correlation* between autistic traits and STEM career choice did not seemingly extend to those with autism being "more likely to work in STEM occupations, compared with controls." Going back to that 'what is being tested' issue, the AQ for example, might also be picking up something linked to "loneliness, social anxiety, depression, and anxiety" [3] or even something approaching the schizophrenia spectrum (see here) or personality disorder (see here). Indeed, one might have to entertain the idea that the definition 'autistic traits' may not tell the whole story in this study.

I have to admit to being still a little sceptical of big psychological theories such as the EMB or the E-S theory of sex differences. The reason? Whilst attractive in their compartmentalising nature, real life is often far from being so clear-cut and linear. The fact also that an important part of the evidence behind such theories remains a little 'fluffy' (see here for example) cannot be readily brushed under the scientific carpet. As for the use of the term 'brain types', well, I can see what the authors were getting at, but I'm not convinced such terminology is particularly useful. 'Brain types' kinda sits in the same category as 'neurotypical' (see here). I was also drawn to the fact that the authors have to explicitly say that their results don't mean that "autistic people lack empathy" and that "autistic people are not hyper-male in general." It kinda tells you how some of the history behind these theories shows that they have not exactly been received with open arms by many.

But even with all that, the Greenberg results cannot be just discounted, and more research on this topic is indicated.

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[1] Greenberg DM. et al. Testing the Empathizing-Systemizing theory of sex differences and the Extreme Male Brain theory of autism in half a million people. Proc Natl Acad Sci U S A. 2018 Nov 12. pii: 201811032.

[2] Ruzich E. et al. Sex and STEM Occupation Predict Autism-Spectrum Quotient (AQ) Scores in Half a Million People. PLoS One. 2015 Oct 21;10(10):e0141229.

[3] Reed P. et al. Loneliness and Social Anxiety Mediate the Relationship between Autism Quotient and Quality of Life in University Students. Journal of Developmental and Physical Disabilities. 2016; 28: 723-733.

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Wednesday, 14 November 2018

Vitamin D supplementation and autism: more work needed on the biochemistry of vitamin D metabolism

The findings reported by Conor Kerley and colleagues [1] provide the brief blogging fodder today. Researchers, who are no stranger to the research area that is vitamin D and autism (see here), decided to conduct a 'post-hoc analysis' of data from two controlled trials where vitamin D supplementation was experimentally tested for children with autism and children with asthma. They were specifically looking at the "serum response to vitamin D supplementation" rather that the amount of vitamin D supplemented as potentially being important to the clinical results obtained. They concluded that "children with ASD [autism spectrum disorder] had a lower increase in 25(OH)D levels with supplementation." Further: "Potential mechanisms include altered absorption/metabolism as well as well genetic factors."

Bearing in mind the relatively small participant group numbers used and comparisons between kids with autism and kids with asthma without any other 'asymptomatic' group involvement, I was really rather interested in the Kerley findings. This was a research group who previously concluded that vitamin D supplementation did little for their cohort of autistic children under experimental conditions [2]. Now they're perhaps suggesting that there may have been valid biological reasons behind such results with respect to the biochemistry/metabolism behind vitamin D with such issues potentially affecting how much vitamin D supplementation is required to suitably raise vitamin D levels.

Of course this is not necessarily a new finding. Science has already started to look at the genetics/biology of vitamin D metabolism in relation to autism (see here and see here) and continues to do so [3]. It also converges with the idea that a deficiency/insufficiency of vitamin D is an important clinical finding but does not necessarily mean that a universal dose of vitamin D supplementation will 'fix anything' (see here for another example in another label).

"Clinical and research work relating to vitamin D is ASD should measure 25(OHO)D response to supplementation to assess therapeutic doses." I can't argue with such sentiments on the basis of the results observed. Working back from sayings such as 'the dose makes the poison', it appears that for some on the autism spectrum, that dose may not be the same as everyone else...

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[1] Kerley CP. et al. Blunted serum 25(OH)D response to vitamin D3 supplementation in children with autism. Nutr Neurosci. 2018 Oct 10:1-6.

[2] Kerley CP. et al. Lack of effect of vitamin D3 supplementation in autism: a 20-week, placebo-controlled RCT. Arch Dis Child. 2017 Nov;102(11):1030-1036.

[3] Biswas S. et al. Fok-I, Bsm-I, and Taq-I Variants of Vitamin D Receptor Polymorphism in the Development of Autism Spectrum Disorder: A Literature Review. Cureus. 2018 Aug 29;10(8):e3228.

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Tuesday, 13 November 2018

SEED says... risk of overweight/obesity in autism is heightened

SEED - The Study to Explore Early Development - provides yet more discussion fodder today as I bring the findings reported by Susan Levy and colleagues [1] to the blogging table. This time around the focus was on the risk of being overweight and/or obese in relation to a diagnosis of autism and the conclusion that: "Prevention of excess weight gain in children with ASD [autism spectrum disorder], especially those with severe symptoms, and in children with developmental delays/disorders represents an important target for intervention" on the basis of results observed.

It's not exactly a new thing to observe that those diagnosed with autism are perhaps at a greater risk of being overweight and/or obese (see here). There are a multitude of possible reasons behind such statistics covering everything from research showing those on the autism spectrum to typically be more sedentary than peers (see here) (bearing in mind the idea that 'you can't outrun a bad diet'), to a heightened risk of receiving medicines that list weight issues as a side-effect (see here) to a possible role for over-represented comorbidity (see here) with regard to weight issues. The net results however is the same: being diagnosed with an autism spectrum disorder places someone at a heightened risk of being overweight or obese.

Levy et al compared three groups of young children - "2-5 years of age" - classified by a diagnosis of autism spectrum disorder (ASD) or developmental delay/disorder or classed as a general population controls (i.e. asymptomatic). Importantly they describe how height and weight were "measured during a clinical visit" thus removing the reliance on 'at home' or routine records measurements [2] and the risk of bias that they can sometimes bring. Researchers also gathered background information on various co-occurring conditions/diagnoses.

Results: "The odds of overweight/obesity were 1.57 times... higher in children with ASD than general population controls and 1.38 times... higher in children with developmental delays/disorders than general population controls." One needs to be bear in mind the quite young age of participants when putting that last sentence into some context. Also: "Among children with ASD, those with severe ASD symptoms were 1.7 times... more likely to be classified as overweight/obese compared with children with mild ASD symptoms."

There's little more to say about such findings other than autism or autistic traits, yet again, seems to place someone as a quite significant disadvantage when it comes to their physical health and wellbeing. Now, the important question: what can be done about it?

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[1] Levy SE. et al. Relationship of Weight Outcomes, Co-Occurring Conditions, and Severity of Autism Spectrum Disorder in the Study to Explore Early Development. The Journal of Pediatrics. 2018. 9 Oct.

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Monday, 12 November 2018

Quality of life and autism continued

"In this study it was found that psychiatric comorbidity, sleeping difficulty, intellectual disability, maladaptive behavior, adaptive functioning, autism symptomatology, main daytime activity and residence were associated with QoL [quality of life], independent of respondent type."

So concluded the findings reported by Ane Knüppel and colleagues [1] continuing an important research theme looking at quality of life with autism in mind (see here and see here and see here). There's nothing specifically novel about the factors reported on as affecting quality of life (QoL) where a diagnosis of autism is mentioned (mental health issues, autism severity, comorbidity, activities, social inclusion) but the fact that authors drew on data from both self-reports and proxy-reports is important and perhaps provides an important dual perspective. Indeed as the authors noted: "Proxy-reported QoL is different from self-reported QoL and should be considered as an alternative source of information." Similar sentiments have been expressed recently (see here).

Having previously talked [2] about the properties of the specific instrument used to gauge QoL with autism in mind, the authors relied on responses on the INICO-FEAPS scale in their investigation. More than 1700 participants with autism completed the scale where: "For 165 individuals with ASD [autism spectrum disorder], self-reports only were available, and for 863 individuals with ASD, only parental proxy-reports were available." The scale itself is pretty comprehensive, consisting of "72 items divided into the following eight subdomains: self-determination, rights, emotional wellbeing, social inclusion, personal development, interpersonal relationships, material wellbeing, and physical wellbeing." A higher score on the INICO-FEAPS scale denotes a higher QoL 'level'. Various other measures were also included for study; some of them based on the setting of the study in Denmark and the fact that Scandinavian countries are particularly 'geared up' for collecting all-manner of details on the basis of various national registries held on the population.

Alongside the results suggesting that various factors seemed to be important to QoL, there were some details to consider. So: "Across all respondent groups, the lowest rated QoL domains were emotional wellbeing (range of means = 71.10–74.05) and interpersonal relationships (range of means = 65.07–71.88), and the highest rated QoL domains were rights (range of means = 83.79–86.21) and material wellbeing." Further, researchers also observed that being employed or in education also correlated with a higher QoL score "compared to individuals without any regular daytime activity" and "significant associations were found for all respondent groups, with lower levels of QoL among individuals living with their parents... and among individuals with ASD living outside the family home with support... compared to individuals living independently without support."

I was also interested in the idea discussed by the authors that: "treating psychiatric comorbidity, reducing maladaptive behavior, raising the level of independence, and offering individuals with ASD an opportunity to be involved in any job-related occupation or to receive education may raise the level of QoL." 'Treating psychiatric comorbidity' is already a research and clinical priority when it comes to autism (see here and see here). Yes, science needs to do a lot better in terms of establishing the 'hows-and-whys' of such comorbidity being over-represented alongside autism but there are some important themes starting to emerge (see here) including that looking at core autism symptoms as being potential risk factors for the appearance of such issues. And once again we can look to an important group of people for further clues as to how such psychiatric issues are indeed perhaps more 'core' than comorbidity (see here).

Although 'reducing maladaptive behaviour' potentially covers a lot of 'challenging' ground - "Behavior classified as self-destructive, breaking belongings, defiant, disruptive, hurtful to others and/or socially offensive" - I don't think anyone would seriously argue against the idea that such behaviours are neither good for the individual nor good for those around them. I'm minded to suggest that the reason(s) for such behaviour are likely to be complex (see here and see here), but one thing that could be useful would be to look at some of the research on particular 'profiles' being present and connected to autism and beyond (see here) as a starting point.

And then there is also the suggestion of a possible effect for society more generally, as in ensuring that education and employment opportunities are available to all and making 'an inclusive society' a priority...

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[1] Knüppel A. et al. Quality of life in adolescents and adults with autism spectrum disorder: Results from a nationwide Danish survey using self-reports and parental proxy-reports. Research in Developmental Disabilities. 2018; 83: 247-259.

[2] Knüppel A. et al. Psychometric properties of the INICO-FEAPS scale in a Danish sample with autism spectrum disorders. Research in Developmental Disabilities. 2018; 75: 11-21.

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Saturday, 10 November 2018

"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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