By Dorta Associates | January 31, 2019 at 02:01 PM EST | No Comments
An important study was just published in Nature Genetics. The researchers obtained large samples with over 20,000 either clinically diagnosed or self-identified patients with ADHD whose genes we could compare to 35,000 non-diagnosed individuals. In these large gene data sets, the study used state of the art genetic modeling to map 12 key gene locations related to ADHD. These locations are generally consistent with other smaller studies which is important since it supports the generalizability of the gene loci with varied samples.
They identified 12 gene loci (for about 22% of the gene heritability in ADHD) and a clustering of genes on chromosome 1. The study firmly supports the polygenetic model of ADHD (multiple risk genes have to be present to have the disorder).
The genes mapped are known to be related to varied self-regulation processes and neurodevelopmental factors including dopamine levels in the brain, neuronal migration, synapse formation and language development.
The study also supports that ADHD symptoms are an extreme expression of normal behaviors. The highly heritable genes mapped have adapted with evolution to be resistant to mutation and loss of function. This supports that ADHD is a disorder where its the abnormal "quantity" of expression of a behavior to a situational demand that is the problem.
The identified genes are also related to adverse health outcomes including smoking, depression, obesity, diabetes, and a range of other impulse related problems.
The study also linked ADHD with difficulties in school including completing less formal schooling.
By Dorta Associates | January 12, 2019 at 12:44 PM EST | No Comments
Many people ask if ADHD is over-diagnosed in children.I get comments from parents like, “So many children in my kid’s school are taking medication for ADHD, what’s going on.” The scientific answer is tricky.
We first have to clarify what over-diagnosis is.In scientific terms, it is a false positive, or diagnosing a child with ADHD who in fact doesn’t have the condition.Another error that can occur is a false negative or failing to diagnosis ADHD in a child who actually does suffer from the condition.Since we do not have a 100% accurate test for the ADHD diagnosis (by the way few conditions in medicine have such tests), we rely on expert diagnosis using varied methods.Yes, this method is imperfect.We are constantly doing research to improve diagnostic accuracy, but don’t be misled to think that ADHD is not a real condition.The science behind the validity of the diagnosis is excellent.
It is also important to understand that ADHD is a common childhood condition and studies across different countries find a prevalence rate of somewhere between 3 to 7 percent of children suffer from this condition.A world-wide systematic study found the rate at 5%.Boys have a higher rate of this condition than girls.
What we have also discovered that characteristics such as age, race, gender, and where you live affect prevalence rate.If your child is older, Caucasian, male, and you live in an urban setting, he is more likely to get a diagnosis and be in that 3 to 7 percent group.
We have also discovered that over-diagnosis, or false positive errors, are more likely to occur when the diagnosis is based on a single office visit with a doctor who does not use a multi-model assessment procedure (this also leads to a higher false negative rate by the way).It is important to realize that the actual problem is that there is more mis-diagnosis overall.
One study found that only 59% of children diagnosed in single office visit mainly by pediatricians were diagnosed correctly (this includes false positive and false negatives).This was established by having a second doctor who rigorously followed practice guidelines of multimodal assessment to confirm the initial diagnosis.In an even more carefully done study, the over-diagnosis rate or false positive was 17% in cases reviewed, but not all these children were actually treated with medication.
Diagnostic errors can therefor lead to two problems.The first is inappropriate treatment such as giving a child medication when he/she does not need it, but also a failure to treat, which is not giving medication to a child who needs it.Interestingly, while errors are high in some settings as discussed above, treatment with medication is not over the expected prevalence rates.The medication rate for ADHD was 6% as reported in 2011 for school aged children in the US.This is in line with prevalence rates, but of concern is that this number is far higher in some communities and has crept up over the years overall.Interestingly, treatment rates in Europe are lower even though their prevalence rates are similar to ours (an example of how “culture” can affect treatment decision-making).We also know in the US that Caucasian boys are treated more than females and other races with medication.Studies show that Caucasian boys are twice more likely to get medication treatment than African-American boys.Thus, there is a percentage of children in these other groups who are not being treated (who may benefit from medication treatment). Many factors including access to care affect treatment rates.
The “big” result here is that the initial diagnosis of ADHD has to be done carefully.The doctor should follow research-based practice guidelines that use multi-modal assessment procedures.It is also important that all children with ADHD get screened for learning disabilities since a child with ADHD is at far greater risk for these conditions as well.
By Dorta Associates | November 27, 2018 at 12:42 PM EST | No Comments
Parents ask me this question frequently, but to answer it accurately a brief review of genetics helps. Most people believe that a trait like eye color or a disease that is “genetic” is passed down directly from parent to child (if you have the gene you have the problem).This form of heritability is referred to as a dominant transmission.Dyslexia, and for that matter the vast majority of the developmental problems children have, dominant transmission is exceedingly rare.It is more like eye color (where at least eight genes are involved in determining your child’s eye color).There are rare families where dyslexia has been shown to have a more dominant-like sort of transmission, but rare is the key word.
Dyslexia from a genetic model is often referred to a multifactorial or polygenetic mode of transmission again in the vast majority of families.This means that for children to have dyslexia multiple gene anomalies (i.e., glitches) have to be present.It is also important to understand that gene glitches produce a liability (a risk) for the reading problem that can be affected positively or negatively by the child’s environment (the big one there is quality of early reading instruction).
Thus, a child with a significant liability for dyslexia (multiple genes with glitches) who receives poor quality reading instruction is most likely to develop dyslexia.
Studies involving twins are an important method in genetic heritability research.Remember that identical twins (called monozygotic twins) have 100% overlap in gene copies were as fraternal twins (called dyzogotic twins) share 50% overlap in gene copies.By studying twins who have grown up together and apart we can determine the heritability of dyslexia.In several large studies researchers find that reading disorder is about 60-70% heritable and environmental factors account for about 30% of the expression of the disorder (about 10% of the heritability is unknown).Heritability also increases a lot in children of higher socioeconomic backgrounds and decreases in children who come from poverty or from less educated parents (for example in twins of well-educated parents the heritability is about 70% and from less well educated parents about 50%).
Lastly, there are several genes that have been identified in dyslexia.The names and location of these genes are less important as to an understanding of what they all seem to do.The majority of genes identified in dyslexia affect something called neuronal migration.This is a process where genes direct the formation and location of synapses across the brain.What researchers have found is that this process is misdirected and less well organized.In uncommon cases, clumps of brain matter don’t form at all.
There are some important take homes for parents.Yes dyslexia is “genetic” and if you have one child with dyslexia, your other children are likely at higher risk.So in those children keep an eye out for early reading problems and intervene early.Remember the research shows that in most children the quality of reading instruction is just as important as the genes, including those you passed down for his/her beautiful eyes.