vrijdag 26 februari 2010

Non genetic factors that have been proposed as causes of ADHD

Criticisms of the concept of ADHD as a disorder are often linked to suggestions that ADHD develops as a result of bad parenting or too much television or some other societal factor – What is the evidence for the influence of these factors on ADHD? –
Note: some of the causes here are likely to lead to more profound problems then pure ADHD, or a different cognitive profile. But they are often not distinguished in the diagnostic process and are likely to make up a subgroup of people diagnosed with ADHD .
We will split causes into two groups because causes not affecting the vast majority of children in society today are unlikely to have a significant effect on the incidence of ADHD ( we would not then find so high a genetic effect.)
If one parent has ADHD your risk of having ADHD is increased 500%. It is more inheritable then height, any personality factor or any psychiatric disorder and is linked to inheritance of a cluster of genes. For example studies in a number of countries comparing fraternal twins (50% same genes) with identical twins (100% same genes) both being brought up together (so that environment should be similar) Found that if is 0.8 to 0.97.

Because of the high heritability, as already said it is not possible that any of these play a significant causal role in ADHD. Could they perhaps play a tiny role – We will look at the evidence for each…


Blaming parents for their kids has always been a satisfying neighbourly activity. (So... I am bitter!). Freud elevated such gossip to intellectual respectability, paving the way for some great twentieth century injustices ‘Schizophrenogenic’ mothers were responsible for their children’s development of schizophrenia (Lidz);’ refrigerator mothers’ for the development of autism (Bettelheim). These theories are now completely discredited.
This school of thought has applied itself to ADHD, but is thankfully now dwindled to the fringes of mental health care in many countries. To be fair, theory has moved with the times, replacing the misogyny of Bettelheim and Lidz with a more PC misanthropy; parents not mothers alone are now held jointly responsible for their children’s’ mental disorders.
Is there any factual basis for a causal link between poor parenting and ADHD?
Bettelheim confused cause and effect, for example many parents of autistic children to avoid eye contact with the child if they know the child will be upset by it. That is the parental lack of eye contact is in response to the children’s autism and not the other way around.
Similar causal relationships between the child’s ADHD and parenting have been demonstrated i.e. CHILDREN’S’ ADHD SYMPTOMS TRIGGER APPARENTLY POORER PARENTING BEHAVIOURS not the other way around e.g., Barkley and Cunningham (1979) found that negative parenting behaviours spontaneously improved after children with ADHD were placed on medication.
Poor parenting must have some consequences for the child?
Some studies found weak evidence for ADHD developing with some parenting styles, but failed to control for parental ADHD. (That is if the parenting behaviours are associated with parental ADHD, the child’s ADHD is likely to be hereditary) An example is Carlson, Jacobvitz and Sroufe (1995) who found that intrusive, insensitive mothers were more likely to have insecurely attached kids with inattention and hyperactivity symptoms
Some research suggests that children who showed greater persistence of ADHD symptoms from preschool to early childhood are more likely to have parents with poorer parenting skills. THUS PARENTING SKILLS PLAY LITTLE PART IN THE DEVELOPMENT OF ADHD BUT BETTERQUALITY PARENTING MAY BRING BETTER OUTCOMES FOR CHILDREN WITH ADHD.
Following from that -Do parents of children with ADHD have to be better parents then parents of other children?
Seems like it: a study of Posner’s found that infants with the DRD4 7 rpt allele (highly associated with the personality trait of sensation seeking and ADHD) developed less sensation seeking behaviour as toddlers when better quality parental interactions were assessed by researchers when the children were infants. The children without the allele developed normally irrespective of ratings of parental quality. None of the parents were assessed as poor IN OTHER WORDS ONE OF THE GENES ASSOCIATED WITH ADHD SEEMS TO HYPERSENSITIVE TO VERY GOOD PARENTING SKILLS.
Are Parents with ADHD especially bad parents for children with ADHD?
No. A lot of attention has focused on factors such as lack of structure and inconsistency in ADHD parents, but it seems there are compensatory factors.
See (Thompson & Sonuga-Barke, 2008) who found THAT PARENTAL RESPONSE TO CHILDREN WITH ADHD ARE MORE AFFECTIONATE AND POSITIVE WHEN THE MOTHER ALSO HAS HIGH ADHD SYMPTOMS (so that maternal ADHD seems to protect against the negative effect of the child’s ADHD on parenting behaviours described above
Conclusion: There is no evidence that poor parenting causes ADHD symptoms. However it is tough for parents of children with ADHD: Research shows that not only is it harder for parents to avoid responding more negatively to children with ADHD, but children with the DRD4 7 rpt allele , weakly associated with ADHD seem to be abnormally positively responsive to greater parenting quality . Disruptive and aggressive behaviour and conduct disorders are somewhat linked to parenting and conflict at home- and it may be that children with ADHD are more vulnerable to these additional problems.
Children who have been sexually abused AND develop PTSD (post traumatic stress disorder) can exhibit greater activity and impulsivity (children who have been sexually abused and do not develop PTSD tend to show more depressive symptoms). So extreme trauma can (but not in every case) lead to impulsivity and higher levels of activity.
Since 1979 US attorney general has warned that smoking during pregnancy can harm the foetus and retard growth. It has became s associated with a range of child development anomalies, including low birth weight (LBW), reductions in growth, learning and/ or cognitive problems and increased motor One route is
Maternal smoking-in pregnancy can cause LBW in addition to other effects of nicotine toxicity. Studies that have controlled for LBW in order to look at nicotine toxicity may have underestimated problems caused by maternal smoking. The Link to ADHD is not clearly established as many studies have concentrated on the effect on conduct problems rather than ADHD. However prenatal nicotine found to be among the strongest correlates in Massachusetts General Hospital study of pre and prenatal correlates of ADHD. A weakness of this study was that it did not control for maternal ADHD. If parents with ADHD are more likely to smoke then correlation may be only apparent, that is the association id due to genetics rather than smoking However ADHD does not seem to predict smoking, those with comorbid ADHD and CD are most likely to smoke.
This suggests a further study weakness in that researchers did not screen for maternal ADHD and CD, which will make a mother more likely to smoke and separately from the direct effects of smoking more likely to pass both disorders to her child.

Conclusion: Small but robust effect has survived in the most well controlled studies. No real research into the exact nature of the effect of smoking on development. Is it the same as ADHD with a non smoking mother?

Several studies have found that outdoor related activities reduced ADHD symptoms e.g. (Kuo & Taylor, 2004)); other research suggests that we all benefit from exposure to nature. Older people live longer if there is a park nearby; all other factors being the same, students do better in a cognitive test if their dorms overlook a garden. Louv extended this argument to suggest that all children suffer from a ‘nature deficit disorder’ (rather a lot!)Causing among other things attentional problems, and thus by extension ADHD. But as far as I know no studies used a group of control children to see if nature also produced positive benefits for children without ADHD. Other research suggests that we all benefit from exposure to nature
Conclusion Lack of exposure to nature is not a trigger for development of ADHD .Increased exposure to nature probably has beneficial effects for children with ADHD (not all children with ADHD, see photo), but we have reason to think this applies to all children.
Very common experiences that could affect almost all twin studies, thus not ruled out by strong genetic correlation
Dietary factors are usually considered to be more or less ubiquitous in the western world and therefore to lie in the second class of factors. I have followed that convention here, but have some reservations, see my remarks on omega 3.
High sugar intake does not explain ADHD symptoms. (Wolraich, Wilson, & White, 1985). But antibiotic sugar interactions in a small number of children are under investigation
Feingold theory that allergic reactions to chemicals in food could affect behaviour. Early studies did not bear this out-. But more recent studies have suggested a subset of children may be at slight risk, the design of some of these studies has been criticized.
As yet very limited evidence of other dietary intolerances in a sub group of people with ADHD that my worsen ADHD symptoms; gluten, dairy, citrus fruits.

The Evidence is generally considered to show that dietary shortage of omega 3 ubiquitous in many parts of western world.Theoretical considerations suggest some children may be genetically less good at conversion of precursor molecules therefore genetically more susceptible to effects of modern diet
Dietary fatty acids play a preventive role against a number of disorders such as cardiovascular disease, and since they help form the neuronal membrane they may affect mood and behaviour. Theoretical case is good. Speculation therefore that a DFA deficiency is involved in schizophrenia, LDs and ADHD
I have been rather sceptical about this for a number of reasons the ‘Durham’ studies were much publicised in Brussels but we were mislead about the quality of the evidence. Also there does not seem to be much variation in ADHD rates with variation in national diets e.g. the Cretan diet is said to be the healthiest diet in the world, a so ‘super Mediterranean’ diet. Lots of olive oil (30% daily calories), fish, low red meat, low sugar, lots of vegetables, especially green ones, low alcohol. Consequently low rates of heart disease, of some cancers, of Parkinson’s and Alzheimer’s etc- yet the Cretan ADHD rate seems to be at least as high as anywhere else in Europe. - 8.8 % in boys, 4.4 % for girls (Skounti, Mpitzaraki, Vamvoukas, & Galanakis, 2006)
Evidence: Some early studies found children with ADHD had lower serum free fatty acid levels. (Bekaroglu, Aslan, Gedik, & Deger, 1996) Studies into supplementation of diet of children with ADHD have had mixed results; some even finding a negative effect. Other studies have found that supplementation with a full array of fatty acids did lead to significant improvements in ADHD symptoms. (Richardson & Puri, 2002)A study comparing diet of adolescents with and without ADHD found that despite the ADHD kids consuming similar levels of DHAs, blood levels of the omega 3s were much lower. (Colter, Cutler, & Meckling, 2008) Supporting suggestions of differences in metabolic handling of fatty acids in ADHD. Similar results had previously been obtained in Taiwan.
Lower levels of fatty acids are also found in adults with ADHD, but were not found to be related to symptom severity.
Summary: There is evidence of lower blood levels of fatty acids in people with ADHD compared with normals eating a similar diet. This suggests a problem with metabolism for least some people with ADHD. Evidence of the benefits of dietary supplementation in righting this problem, has been very mixed but is growing.
Research by Dr Konofal in France has found low levels of Iron in the blood of many children with ADHD, with the lowest blood levels being linked to most marked ADHD symptoms. Again (as in the case of omega 3) there was nothing abnormal about the children’s diet. This suggests dietary supplementation could help a subgroup of children with ADHD.

Takes me back, Mum used to take me to the doctors complaining about my low activity level in the fifties and sixties. He would say my iron was a bit low; start iron supplementation and then again the following year because Iron was still a bit low and so on. If anything I became more inactive possibly because I was stuck to the fridge, in a magnetic sort of way.

Studies show that effects of media on children are governed more by the content of programmes watched, rather than by number hours of TV watching. In fact hours of educational TV watching is linked positively to school achievement. Hours of watching violent TV and video programmes is linked to aggression (not ADHD) with by far the most effect carried by children with other signs of vulnerability for developing aggressive behaviour. Many children are able to watch violent TV with no effects on aggressive behaviour. These facts together suggest a genotype environment interaction.
A few studies however have suggested a link between TV and attention (Christakis, Zimmerman, DiGuiseppe, & McCarty, 2004) Linked the No of hours spent watching TV between 1 to 3 years to attention problems at 7 years.3 hrs TV a day between 1 and 3 years old leading to a 30% increased risk- Compared with kids watching no TV.But study had some big weaknesses- did not control for maternal ADHD or attentional problems already developed at 1-3 years. Latter especially, is in my experience very likely to increase the parental temptation to encourage the child to watch more TV.
One study did find a clear link between type of TV watched and temporary attentional symptoms in 4 to 5 year old normal children. The children watched 30 minutes TV, one group watching Power Rangers, which was fast paced and believed to require frequent attentional shifts, the others an educational program . The children were watched at free play afterwards and the group who had watched fast television showed more activity changes.
Conclusion: whilst there is a clear link between watching violent TV and aggressive behaviour for some more vulnerable children (with and without ADHD). The link between TV watching and core ADHD symptoms is as yet unclear. There may be small effects linked to the pacing and content of the programme.
Note: A factor that increases the chance of having ADHD by 30% is a very small affect. Say the chance of one person taken at random in the general population having ADHD in the general population is 5 %( or 1 in 20) then if you have some factor that increases your risk by 30%. Your chance of having ADHD is now increased to 6.5%.

Increases the chance of a whole lot of developmental risk factors including ADHD. LBW h as a lot of causes – prematurely birth., growth problems in the womb Further Advances in post natal care since the sixties onward have increased the survival rates of children with low birth rate (1500g >2500g and moderately low birth rate) And now children with birth weights less than 1500 grams can survive. (Very low birth rate)
Since 1980 rates of cerebral palsy and other disabilities stayed constant among children with LBW (about 1 in 12) whilst survival rates increased. Total rate of disabilities in developing countries therefore increased. In addition may be other neurological problems such as spatial, motor and verbal deficits, behavioural problems and hyperactivity
Low birth weight increases risk of ADHD. 16% of children with extremely low birth weight(less than a thousand grams) have ADHD compared with 5 % of controls but may have been largely explained by low birth weight developmental delay.
In conclusion very low birthrate may lead to a doubling or in combination with other risk factors of the chance of developing ADHD. Through this is often combined with lowered IQ and general, neuorocognitive problems the risk for ADHD does seem to be specific
Heavy drinking in pregnancy may lead to fetal alcohol spectrum disorders. Although FAS leads to severe cognitive and behavioural problems association with ADHD is not clear. Because even category 1 FAS which includes physical abnormalities is often not diagnosed (5 categories of severity), it’s very possible that some cases of FAS are misdiagnosed as ADHD.

POPs are persistent organic pollutants including DDT, PCBs, dioxins very many having been released into the environment in the twentieth century with little knowledge of their effects on the nervous system. All are lipophilic (stored in human fat) and persistent in the environment.
PCBs have been of particular concern; despite now being banned they are ubiquitous in the environment; not biodegradable found in whale blubber, the arctic seal and human placenta... not biodegradable and have caused cognitive problems in the children of woman exposed to high levels in industrial accidents (among other things).
The big question is what does lower grade background exposure such as the 2 to 10 ppb do to human populations? Known to affect cognitive development of the foetus, theoretically thought likely to interact with hormone and dopamine systems. A number of studies have found that higher background levels of PCBs in children’s tissue links to increased motor and cognitive problems and executive level functioning problems, with breast feeding showing some protective effects. (Vreugdenhil, Mulder, & Emmen, 2004) PCP exposure does not correlate with hyperactivity but to problems with executive functioning
High levels of Pre and post natal heavy metal exposure is known to - lead to multiple motor sensory and cognitive impairments that is clearly different from ADHD.
What about lower levels of heavy metals such as lead, can they lead to ADHD like behaviours?
We have increasingly more info about the dangers of low levels of lead.
The WHO safe level was lowered from 25 Mg/dcl WHO to 10mcg/ dcl in 1991 Recent call to lower safe threshold to 5 mcg/dcl. (Chiodio, Jacobson, & Jacobson, 2004) Found an association with attention problems at levels as low as this. Average blood lead level kids in the US is 2-3mcg/dcl Can interfere with synapse formation and affect impulse control among other things.
Therefore quite low level exposures to lead (1 to 10mcg) correlate with lowered IQ and attention problems and could account for a percentage of children diagnosed with ADHD.
‘Acceptable’ levels of mercury like lead have dropped as research has shown more about the risks.Neurodevelopmental effects of mercury most notable on motor and visuospatial problems rather than attention but US national Academy of sciences estimated that 60,000 children at risk of affects of mercury exposure prenatally per year

Replaced lead in petrol- but little known about its effects

The prophet Kryon has said that Indigo children (‘who are often misdiagnosed with ADHD’) represent a leap in human evolution and are here to show humanity the way to a higher vibratory plane.
Whilst I could kiss Kryon for his positive a view of us, the prophet presents no evidence ... and such views are potentially harmful to children with ADHD

you might also be interested in

ADHD- A social construct?

Chiodio, L., Jacobson, S., & Jacobson, J. (2004). Neurodevolopmental effects of postnatal lead exposures at very low lead levels. Neurotoxology and Teratology , 359-364.
Christakis, D., Zimmerman, F., DiGuiseppe, D., & McCarty, C. (2004). Early television exposure and subsequent attentional problems in children. Pediatrics. , 917-918.
Dankearts, M., & Sonuga-Barke, E. e. (2010). The quality of life in children withaAttention defecit/ hyperactivity disorder; a systematic review. European Journal of Child & Adolescant Psychiatry , 83-105.
Kuo, F. E., & Taylor, A. (2004). A potential natural treatment for attention defecit/hyperactity disorder: Evidence from a national study. American Journal of Public Health , 1580-1586.
Richardson, A., & Puri, B. K. (2002). A randomized double-blind, placebo controlled study of the effects of supplementation with highly unsaturated fatty acids on ADHD-related symptoms in children with specific learning disabilities. Progress in Neuro-pyschopharmacology and Biological psychiatry , 2234-239.
Skounti, M. P., Mpitzaraki, K., Vamvoukas, M., & Galanakis, E. (2006). Attention-defecit / hyperactivity disorder in schoolchildren in Crete. Acta Paedeatrica , 658-663.
Thompson, M. J., & Sonuga-Barke, E. (2008). Do maternal attention defecit/hyperactivity symptoms excaberate or ameliorate the negative effects of child attention-defecit /hyperactivity disorder symptoms on parenting? . Development and Pyschopathology , 121-137.

1 opmerking:

generic viagra online zei

Thanks for making aware the people about ADHD. i like it so much keep posting and updating the blog.

Smith ALan