Tuesday, 19 June 2018

"Greater ADHD symptom severity was associated with higher odds for feeling less happy"

Of course correlation does not necessarily equal causation, but the *correlative* results published by Andrew Stickley and colleagues [1] observing that: "Greater ADHD [attention-deficit hyperactivity disordersymptom severity was associated with higher odds for feeling less happy" were worthy of some blogging attention.

Drawing on data derived from the 2007 Adult Psychiatric Morbidity Survey based here in Blighty, researchers tackled quite an important question: how do ADHD signs and symptoms potentially impact on happiness?

So: "Information was collected on ADHD symptoms using the Adult ADHD Self-Report Scale (ASRS) Screener, while happiness was assessed with a single (3-point) measure." Including data for over 7000 people - adults aged 18 years and over - researchers observed that important negative relationship between ADHD symptoms and happiness. Alongside, they also noted that various other variables might also play a role in such a [correlative] relationship: "Mood instability (percentage mediated 37.1%), anxiety disorder (35.6%) and depression (29.9%) were all important mediators of the association between ADHD and happiness."

I'm a great believer that we need more of this kind of research asking relatively simple questions about whether someone is happy or not across various different labels and combinations of labels. I reiterate the whole 'correlation does not necessarily equal causation' mantra and the fact that happiness is not a 'setting' switched to the on position every moment of someones life. One also has to be slightly careful about extrapolating the Stickley results to diagnosed ADHD, and the various issues that come with such a diagnosis (including enhanced risk of comorbidity or 'symptoms' of other diagnostic labels).

But it strikes me as 'logical' that the manifestation of certain types of behaviour - hyperactivity, inattentiveness, impulsivity - might not be all that great for a person when it comes to perceived happiness at certain points in life. I say this in the context that a diagnosis of ADHD has already been *linked* to quite a few adverse life events (see here) including some enhanced risk for something like suicidality (see here). One has to wonder therefore, what role happiness might play in the context of such extremes of behaviour, and whether intervention 'for ADHD' (whatever form this might take) might have some important effects on subjective and objective markers of happiness alongside the manifestation of signs and symptoms...


[1] Stickley A. et al. Attention-deficit/hyperactivity disorder symptoms and happiness among adults in the general population. Psychiatry Res. 2018 May 5;265:317-323.


Monday, 18 June 2018

Selective mutism and autism

The findings reported by Hanna Steffenburg and colleagues [1] make for potentially important reading reporting: "In this study of a clinical group of children who were diagnosed with SM [selective mutismand assessed at a center for neurodevelopmental disorders, 63% also met criteria for ASD [autism spectrum disorder]."

Selective mutism (SM) refers to an anxiety disorder typically manifesting during early childhood that affects the use of spoken language in certain social situations such as at school. 'Literally being unable to speak' is a phrase that follows SM in certain contexts, where speech and language skills are not typically affected when and where family or close friends are around. It's not surprising that there is 'overlap' between SM and autism given the characterisation of SM in terms of being "nervous, uneasy or socially awkward" and "stiff, tense or poorly co-ordinated" (minus any sweeping generalisations). And just before you question it, 'poorly-coordinated' is perhaps an under-rated aspect for many people diagnosed as being on the autism spectrum (see here).

Steffenburg and colleagues - including the notable ESSENCE-related name of Christopher Gillberg - sought to examine the possible 'overlap' of SM and autism on the basis that various diagnoses/labels can occur alongside SM; quite a few of them also recognised in relation to autism (see here). Approaching 100 children/young adults diagnosed with selective mutism were assessed at the premier 'autism spectrum conditions' clinic in Gothenberg, Sweden. The clinical assessment undertaken of course covered the diagnosis of autism but also various cognitive functions too.

Almost two-thirds of those with SM who were assessed also met criteria for an autism spectrum disorder (ASD). Added to that: "A further 20% (n=19) had autistic features that were “subclinical”, but, nevertheless, sufficiently marked to have an impact on everyday life." Only 17% were described as having no ASD symptoms. Those are pretty interesting percentages.

Authors also mention how: "The level of cognitive function was average in more than half of the study group but more than one-third of the study group had a borderline IQ or an ID [intellectual disability]." They use such a finding in the context of the ESSENCE term - Early Symptomatic Syndromes Eliciting Neurodevelopmental Clinical Examinations - where overlapping diagnoses/labels is the rule not the exception.

The implications? Well, screen and keep a continual eye open for autism in cases of SM seems to be an important first implication. That also includes keeping in mind those 'subclinical' signs and symptoms, which could be relevant to discussions about the broader autism phenotype (BAP) (see here) and also that curious DSM-5 diagnostic category known as social communication disorder (SCD) (see here). The focus on 'anxiety' in relation to SM might also be important given the pretty well-established connection between autism and anxiety (see here for example) following in the footsteps of some often forgotten autism research history (take a bow Mildred Creak and colleagues for including the term "acute, excessive and seemingly illogical anxiety"). I'm also minded to mention that given the pretty high rate of autism described in SM by Steffenburg and other researchers, further investigations perhaps need to be directed towards shared biology/genetics as well as shared behavioural presentation? Y'know, along the lines of whether 'comorbidity' might be something more 'core' (see here)?


[1] Steffenburg H. et al. Children with autism spectrum disorders and selective mutism. Neuropsychiatr Dis Treat. 2018 May 7;14:1163-1169.


Saturday, 16 June 2018

ALSPAC says... "Social communication impairments had the strongest association with a depression diagnosis at age 18 years"

ALSPAC mentioned in the title of this post refers to The Avon Longitudinal Study of Parents and Children, one of the premier research initiatives here in Blighty, that has provided all-manner of interesting and important research associations. With autism in mind, ALSPAC has opined on various different research questions (see here and see here for examples) including the issue of a possible 'real' increase in the numbers of children presenting with autistic traits (see here).

On this particular research occasion, ALSPAC was the source data for the findings reported by Dheeraj Rai and colleagues [1] who set out to "compare trajectories of depressive symptoms from ages 10 to 18 years for children with or without ASD [autism spectrum disorder] and autistic traits, to assess associations between ASD and autistic traits and an International Statistical Classification of Diseases, 10th Revision (ICD-10) depression diagnosis at age 18 years, and to explore the importance of genetic confounding and bullying." I might add that some of this authorship group are making some real research waves when it comes to investigations using population registries with autism in mind (see here).

The starting point this time around was the notion that a diagnosis of autism is in no way protective when it comes to a diagnosis of depression and/or the expression of depressive signs and symptoms. Again, it's a topic that has cropped up before on this blog (see here) and is perhaps one of the longer term associations that have been made down the years. The idea that depression or depressive symptoms *might* be something much more than just 'comorbid' in the context of at least 'some' autism is something else that has been banded around the peer-reviewed research literature before (see here) but the evidence base is not particularly big or strong in this area at the moment.

There were a few different research questions asked by Rai et al, including looking at children "with or without ASD or high scores on autistic trait measures" and any relationship(s) with depression and depressive traits. They report findings for over 6000 children ("maximum sample with complete data") where questionnaire items on bullying were also included ("Relational and overt bullying was assessed as separate yes or no items at ages 8, 10, and 13 years using the modified Bullying and Friendship Interview Schedule") alongside various other potentially confounding variables.

Results: "children with ASD and those with higher scores on all autistic trait measures had more depressive symptoms at age 10 years than the general population, and these remained elevated in an upward trajectory until age 18 years." I don't think there's anything too novel in such findings, aside from the observation that depression / depressive symptoms may start quite early on in childhood. I can remember when I started out in autism research a couple of decades ago hearing about depression being typically linked to the onset of adulthood in the context of autism. This current data suggests otherwise.

Next: "Social communication impairments had the strongest association with a depression diagnosis at age 18 years. Findings were robust to adjustment for a range of confounders, including maternal depression and anxiety and the child’s polygenic risk for autism." This is important. What it suggests is that there may something 'more than just comorbid' about depression or depressive symptoms appearing alongside autism or at least in connection to certain autistic traits. I know some people have already taken exception to this possibility alongside the use of the word 'impairment' by the authors. But much like other research on an important bedfellow to depression - anxiety - one may have to entertain the possibility that there may be some enhanced 'predisposition' to something like depression alongside the presentation of autistic traits (see here and see here) perhaps mediated by factors such as rumination and perseveration for example [2]. This doesn't mean that depression is solely a product of autistic traits; merely that certain traits may potentially form an important vulnerability factor. I'm similarly minded to bring in other work from the ALSPAC initiative [3] (including Rai and colleagues as authors) where related findings were mentioned: "Social communication impairments are an important autistic trait in relation to suicidality." This on the basis that depression and suicidality show an important association.

Also: "We found evidence of a substantial role of bullying in contributing to and explaining a higher risk of depression in individuals with ASD and autistic symptoms." Bullying in the context of autism is another long-standing topic (see here). Bullying covers a lot of ground in terms of behaviour and also source (see here). The authors opine that: "Previous work has shown strong links between the experience of bullying and later depression... although confounding could have a role, the association is considered to be at least partially causal." It's also important to note that social-communication 'issues' were reported to be potentially predictive of being bullied according to the authors. The model that then appears hints that the appearance of depression *might* be linked to "reduced self-esteem or social isolation after the bullying" accepting that causality is not established and also not accounting for other variables: "other relevant characteristics, including comorbidities with neurodevelopmental conditions (eg, attention-deficit/hyperactivity disorder) and classroom placement could be important in this association within or outside the context of bullying." That last point is important in the context that autism rarely exists in some sort of diagnostic vacuum (see here).

There are a few caveats attached to the Rai findings that need to be kept in mind outside of any 'correlation does not necessarily equal causation' sentiments. So: "atypical presentations of depression are common in ASD, and our study has the potential for outcome measurement error because we used scales... that have not been adapted for autism." Indeed. I've previously talked about how bipolar disorder for example, might not follow a typical pattern when present in the context of autism (see here). I daresay that this could also hold for other types/forms of depression too. I'm also minded to reiterate that depression, as well as being a heterogeneous condition, also seemingly has many pathways to it. Some of those pathways will include psychological and social variables such as bullying and perhaps even more extremes of 'trauma'; where a diagnosis of PTSD is for example, no stranger to autism (see here). 'Happiness' and perceived quality of life (see here) are also likely to exert an important effect too.

Other pathways to depression seem to be more biologically defined as per depression in the context of physical ailments (see here) that may have a *link* to some autism (see here) or following the use of seemingly common medicines according to recent news reports (see here). I'll also mention that things like physical activity and exercise *seem* to show an important relationship with depression (see here). This could also be pertinent to the data suggesting that physical activity levels are typically not optimal where and when autism is diagnosed (see here). Other factors (fatigue, sleep, etc) also need to be mentioned in the context of depression. In short, there are lots and lots of potential variables to consider [4].

Outside of the important messages from the Rai findings on how depression is over-represented in relation to autism and how social factors like bullying seem to be linked  to it and thus are subsequently 'modifiable', there is another important point to consider: depression is typically treatable. Minus any medical or clinical advice being given or intended, the first step in managing/treating depression is identifying it. Perhaps the Rai findings might serve as a further call to action for preferential screening in the context of autism...


[1] Rai D. et al. Association of Autistic Traits With Depression From Childhood to Age 18 Years. JAMA Psychiatry. 2018 Jun 13.

[2] Patel S. et al. Association between anger rumination and autism symptom severity, depression symptoms, aggression, and general dysregulation in adolescents with autism spectrum disorder. Autism. 2017 Feb;21(2):181-189.

[3] Culpin I. et al. Autistic Traits and Suicidal Thoughts, Plans, and Self-Harm in Late Adolescence: Population-Based Cohort Study. J Am Acad Child Adolesc Psychiatry. 2018 May;57(5):313-320.e6.

[4] Köhler CA. et al. Mapping risk factors for depression across the lifespan: An umbrella review of evidence from meta-analyses and Mendelian randomization studies. J Psychiatr Res. 2018 May 25;103:189-207.


Friday, 15 June 2018

'What really grinds my gears': a "slight uptick' in the estimated prevalence of autism

For those who watch the sometimes 'cutting' TV show called Family Guy, the first part of the title of today's post - "what really grinds my gears" - will make sense. For those who don't, it represents a TV segment offered to one of the main characters of the series, Peter Griffin, during which he aired increasingly bizarre opinions of things that 'irk' him. At the close, he revealed that just about everything 'grinds his gears'.

Whilst I'm not typically a person that is easily irked (much of my early years irking has dissipated as a result of age and my hobby), I was a little put out by the opening sentence included in the news piece published by Bridget Kuehn [1] talking about the most recent autism estimated prevalence figures published by the US CDC [2] (see here for my take). To quote: "A slight uptick in US cases of autism spectrum disorders (ASDs) was detected in 2014 compared with the years between 2010 and 2012, according to a new CDC report."

It was the use of the word 'slight' that furrowed my brow. And how a 15% increase in the estimated autism prevalence rate in the US over 2 years - translating as a move from an estimated 1 in 66 8-years olds being diagnosed to 1 in 59 8-years olds being diagnosed - is somehow inferred to be less important than it actually was. Words matter.

I know prevalence (and incidence) rates (estimated or actual) when it comes to autism can invoke some often heated discussions. Such debates perhaps tie into wider views held about autism, and whether you're of the opinion that autism has always been with us, or autism is a relatively new 'condition'; whether autism is primarily explained by genetics or whether non-genetic environmental factors play a significant role; whether you view autism as a serious public health issue or are more inclined towards the idea of an 'autistic identity'. I'm sure there are other polar opinions to add, but the end result is that [peer-reviewed] data can sometimes become a secondary consideration when it comes to such views and opinions.

Personally, I go with the data. I go with the data that suggest that autism prevalence is still increasing, and not just in the United States (see here and see here for examples). I go with the associated idea that explanations such as 'increasing awareness' and 'diagnostic substitution' probably play some role in the increase, but don't provide a wholly intellectually satisfying explanation for the increasing numbers (see here and see here). I go with the idea that alongside increasing numbers of cases of autism being diagnosed, so more needs to be done in terms of the provision of educational and social support being offered for an often complicated clinical pictures (see here). I also go with the idea that research questions need to be asked (and answered) about what factors could be driving the remarkable increase in autism over the past couple of decades without fear or favour.

I also go with the idea that there needs to be a bit more urgency in the response to such figures. I'm not talking about the use of 'inflammatory' language or soundbites which are bound to make some people nervous or angry. Merely that behind the CDC statistics there are real children and there are families and other loved ones. And they deserve a lot more and a lot better than society is currently providing (see here)...


[1] Kuehn B. Uptick in Autism. JAMA. 2018 Jun 12;319(22):2264.

[2] Baio J. et al. Prevalence of Autism Spectrum Disorder Among Children Aged 8 Years — Autism and Developmental Disabilities Monitoring Network, 11 Sites, United States, 2014. Morbidity and Mortality Weekly Report (MMWR). 2018; 67(6): 1-23.


Thursday, 14 June 2018

"Theme 3: Inadequate Provision for Post-diagnostic Support" for autism

The qualitative findings reported by Laura Crane and colleagues [1] on the topic of autism diagnosis here in Blighty provide some useful information that *could* help make the diagnostic process easier and more 'user-friendly'. The findings also highlight some important gaps in the current mechanisms being utilised...

The paper is open-access but basically set out to examine "the views and experiences of ten autistic adults, ten parents of children on the autism spectrum, and ten professionals involved in autism diagnosis, all based in the United Kingdom (UK)." You'll note that the participant numbers for each individual category weren't huge so one has to be slightly cautious about how representative the results are to the wider autism spectrum. Indeed, although not a fan of the term 'functioning' in relation to autism, I note that only two of the children were diagnosed with a learning (intellectual) disability and over half were diagnosed with Asperger syndrome. Alongside the report that of the 10 adults interviewed, nine were diagnosed with Asperger syndrome and several were educated to degree level or above (4/10), and you might reasonably conclude that this was a study weighted towards the more 'able end of the autism spectrum'. I say that again minus the use of the 'functioning' label but understanding that there are 'parts' of the autism spectrum still very much under-represented in this and other research areas (see here)...

No mind, the authors discuss the themes that emerged during telephone interviews with regards to "three important stages of the diagnostic pathway: (1) accessing a diagnostic service; (2) the diagnostic process; and (3) post-diagnostic support." The results are revealing...

I've zoomed in on one of the themes that emerged from the study: "Theme 3: Inadequate Provision for Post-diagnostic Support." I did this because this is the part of the diagnostic machinery that probably has the longest-term effects and has been covered before on this blog (see here). It's not that I don't for example, accept the importance of "vague and inconsistent routes available for accessing an autism diagnosis" or "professionals’ tendency to focus on negatives, not positives". Merely that post-diagnosis, many children and adults are seemingly left to fend for themselves and/or take up further battles in order to get the help and support they require. This, set in a time of increasing need and continuing finite resources (see here).

Within theme 3 around post-diagnostic services and support, we hear some familiar stories. So: "Getting the diagnosis is only the start of the journey and as far as the paediatrician was concerned, that was the end of the journey" and "[you need someone] to support you and direct you…this is where the system fails" are just two of the examples included in the Crane paper. In other words, tick boxes for getting assessments and diagnoses are ticked, but then 'don't let the door hit you on the way out' sentiments seemingly follow. That's not to blame assessment teams or diagnosing clinicians who do a sterling job often under pressure (see here), merely to point out how the system is current set out.

Another phrase included by the authors adds to the 'inadequate provision' sentiments expressed: "When services were made available to support autistic people and their families, these tend not to be offered until crisis point was reached." It seems that one has to be literally be at the end of ones tether before anything like the resources needed are given out, and even then, in a reactive sense. And thereafter: "when support was provided (and was felt to be useful), financial constraints sometimes meant that services were withdrawn". Such issues were seemingly spread across both child and adult experiences, as the call for "a solid, government-backed organisation that could help rather than these sort of variegated charities that are all struggling financially" went out. What a good idea: a national post-diagnosis autism agency...

I'm also going to highlight the 'lack of emotional support' picked up in the Crane paper. The adults diagnosed with autism certainly "found their involvement in the assessment process both emotional and challenging" because sometimes the very probing questions used as part of the assessment process brought up things that some people were probably trying very hard to forget. I personally think that this is an under-appreciated side of post-diagnosis in the context of autism, where the diagnosis of post-traumatic stress disorder (PTSD) is perhaps 'under-used' (see here) in light of the effects of past traumas (I use the word 'trauma' minus the psychobabble connotations).

Crane et al also provide a dose of reality in terms of what parents go through too before, during and after the diagnostic process for their children. So: "I was literally on my knees anyway…it’s so tiring having boys with Aspergers" and "I felt quite on my own. No-one in my family really understood, I didn’t have any friends that had had similar experiences." Such reports are just as important as the other reports included in their study; illustrating how having a child diagnosed with autism can be a roller coaster of emotions, and the strong requirement for "whole family support needs" including things like respite care (see here). I say all this set against a backdrop, particularly on social media, where parents are sometimes/often castigated for speaking their truth and their reality about raising children on the autism spectrum, seemingly because their narrative doesn't fit the agenda of others. Yes, the views of people with autism / autistic people count, but so do the views of those who raise them too (see here). And social media 'discussions' for example, about 'informed consent' before posting pictures and reciting specific child-rearing events, whilst important, cannot just be solely applied to parents of autistic children either...

There are seemingly lots of things that can be done to improve the diagnostic and post-diagnostic experiences related to autism on the basis of the Crane findings. One would hope that policy - (peer-reviewed) evidence-based policy - would be listening and wanting to change things for the good of all concerned: those on the autism spectrum, their parents and other loved ones and the professionals who do a remarkable job with all-too finite resources. I fear however, that the reality is yet again going to be tied into one solitary question; a question that crops up time and time again: how much is it all going to cost?


[1] Crane L. et al. Autism Diagnosis in the United Kingdom: Perspectives of Autistic Adults, Parents and Professionals. J Autism Developmental Disorders. 2018. June 12.


Wednesday, 13 June 2018

"Gluten-free prescribing is in a state of flux"

Consider this off-core-topic post an extension of previous other off-topic chatter on this blog talking about the prescription of gluten-free foods here in Blighty (see here). On that previous blogging occasion, I discussed a 'head-to-head' debate on whether the prescription of gluten-free foods for conditions such as coeliac disease was still 'relevant' in an age when supermarkets have shelves loaded with gluten-free products as part of a societal fascination with 'going gluten-free'. Whether there may be other models - such as the use of a voucher scheme - that could save time and money yet still ensure that the important use of a gluten-free diet in relation to coeliac disease is maintained and supported.

Well, the recent findings reported by Alex Walker and colleagues [1] add to this debate, and their look at "long-term national trends in gluten-free prescribing, and practice and Clinical Commissioning Group (CCG) level monthly variation in the rate of gluten-free prescribing (per 1000 patients) over time." CCGs by the way, are groups here in England "responsible for the planning and commissioning of health care services for their local area."

Walker et al relied on a retrospective cohort study design that analysed prescribing and spending data from various sources, and covered various geographical areas of England in relation to gluten-free prescribing. Alongside, other potentially pertinent data were included in the statistical mix, for example: "Index of Multiple Deprivation (IMD) score; patients with a long-term health condition (%); patients over 65 (%) and whether each practice is a ‘dispensing practice’ with an in-house pharmacy service (yes or no)."

Results: including data from over 7600 medical practices, authors reported that between July 2012 and June 2013, some 1.8 million prescriptions for gluten-free products were dispensed costing around £25.4 million. Fast forward to the period July 2016 - June 2017 and fewer prescriptions were made: "1.3 million gluten-free prescriptions nationally... with a total expenditure of £18.7 million." This, bearing in mind, that rates of diagnosed coeliac disease are seemingly only going in one direction - up [2].

Researchers also reported that there was "substantial variation in prescribing rates among practices" which was captured by some other reporting on the Walker paper as per bylines such as: "Prescribing of gluten-free products in England differs largely and “without good reason”, researchers have concluded." Indeed Walker and colleagues concluded that much of the geographical discrepancy in the gluten-free prescribing rates was "driven at the CCG level, where there is also a great deal of variation." For some CCGs, the decision was to provide gluten-free prescriptions; for others, there seems to be "a partial or complete withdrawal of prescriptions." A bit of a postcode lottery if you like.

As to those other variables included in the analysis, a few other important details emerged. So: "practices in the most deprived areas had a significantly lower rate of gluten-free prescribing than those in less deprived areas." Further: "We also found that percentage of patients over 65 is strongly associated with gluten-free prescribing, which is unsurprising given that coeliac disease prevalence increases with age." That first finding in relation to deprivation *might* be linked to things like an under-diagnosis of something like coeliac disease in those areas. But it could point to other factors potentially coming into play as well...

At the time of writing / publishing this post, we are still living in the age of austerity here in Blighty. Government in particular, [still] wants to 'balance the books' yet is still expecting national services such as health to provide for the population they serve. Set within that context, and also how health budgets are having to deal with more people with more complex needs, it's probably not surprising that for some geographical areas, 'low hanging fruit' such as gluten-free prescriptions are seen as fair game when it comes to balancing the books. It shouldn't, but there you go.

I do stand by the idea that if things are seemingly 'on the downward slide' in terms of gluten-free prescribing patterns, there may be other models to look at that could help (i.e. that voucher scheme idea). Patients and their relevant organisations need to have a voice in this process to ensure that gluten-free diets are maintained and health does not unduly suffer. Food, for people with coeliac disease - gluten-free food - is medicine, and one should never forget that and the absolute requirement to provide such medical provision.

To close, and entirely unrelated to today's post, I see Belgium have some historical and/or statistical advantage when it comes to the World Cup starting soon...


[1] Walker AJ. et al. Trends, geographical variation and factors associated with prescribing of gluten-free foods in English primary care: a cross-sectional study. BMJ Open. 2018 Apr 16;8(3):e021312.

[2] Holmes GKT. & Muirhead A. Epidemiology of coeliac disease in a single centre in Southern Derbyshire 1958-2014. BMJ Open Gastroenterol. 2017 Apr 1;4(1):e000137.


Tuesday, 12 June 2018

Early lead (Pb) exposure and risk of ADHD: yet more 'nothing good comes from exposure to lead'

Lead (Pb) is a metal that has cropped up more than once on this blog (see here and see here and see here) in relation to early exposure and it's *possible* links to various childhood behaviour(s). As per part of the title of this post - 'nothing good comes from exposure to lead' - there really does seem to be very little good to say about exposure to lead (see here) given an apparent lack of any (advantageous) biological role when it comes to the human body. In short, we should be doing everything we can to ensure that exposure levels for everyone, particularly the very youngest, are kept to an absolute minimum...

The study results published by Yuelong Ji and colleagues [1] add to a pretty large peer-reviewed research literature observing a possible connection between biological lead levels "in early childhood" and risk of childhood psychopathology. They concluded that: "Elevated early childhood blood lead levels increased the risk of ADHD [attention-deficit hyperactivity disorder]."

The source material for the Ji study was the Boston Birth Cohort (a research initiative that has cropped up before on this blog) and specifically the examination of blood lead levels in conjunction with "physician-diagnosed ADHD" in some 1500 infants: "299 ADHD, 1180 neurotypical." Various other co-variates were also included in the statistical mix and sex/gender was analysed as an independent variable. And before you mention it, yes, as per my other musings on the word 'neurotypical' in the context of autism (see here), I'd prefer another term to denote not-ADHD such as er, 'not-ADHD'.

Results: approaching 1 in 10 of the cohort had elevated blood lead levels defined as a value between 5-10 µg/dL. This is quite worrying, particularly as various agencies have started to reduce the cut-offs/definition of a 'safe' level of lead in recent years (see here). For the 8.9% of the cohort with such blood lead levels, authors noted that this was "associated with a 66% increased risk of ADHD." Boys also seemed to be particularly vulnerable to the effects of elevated blood lead levels in relation to ADHD: "Among boys, the association was significantly stronger."

What else?  Well, bearing in mind the observational methodology employed in the Ji study, authors noted that the relationship between blood lead levels and ADHD also seemed to be mediated by other factors. So, the "risk of ADHD in boys was reduced by one-half if the mother had adequate high-density lipoprotein levels or low stress" where high-density lipoprotein (HDL) typically refers to the 'good type of cholesterol' (bearing in mind that biology is rarely so black-and-white) and 'low stress' refers to stress during pregnancy. In effect, whilst early lead exposure (or blood lead levels) may be important when it comes to risk of ADHD, other factors also seem to play a role; some potentially protective, others not so much (see here for example). This is something that has been noted in other studies looking at other heavy metals and neurodevelopmental outcomes (see here).

In conclusion, still nothing good comes from (early) exposure to lead...


[1] Ji Y. et al. A Prospective Birth Cohort Study on Early Childhood Lead Levels and Attention Deficit Hyperactivity Disorder: New Insight on Sex Differences. J Pediatr. 2018 May 8. pii: S0022-3476(18)30488-8.