Developmental Delay & ADHD

Posted by on July 31st, 2012 | No Comments

Dr. Philip Shaw and his research team at the National Institutes of Health studied 234 children with ADHD and compared them with 231 normally developing children. The researchers scanned each of their brains up to 4 times from age 10 to 17. Their research is published in the journal Biological Psychiatry and mirrors similar research previously performed.

Shaw is particularly interested in surface area of the cerebral cortex — the folded gray tissue that makes up the outermost part of the brain and how it develops during childhood. The researchers’ scans showed that frontal cortex development was delayed in frontal brain regions in the group of children with ADHD. The frontal cortex plays a key role for controlling impulsivity and attention.

The researchers found that in normally developing children, the right prefrontal cortex reached half of its peak area at a mean age of 12.7 years. But the children with ADHD children didn’t reach that mark until 14.6 years; a delay of almost 2 years.

“As other components of cortical development are also delayed, this suggests there is a global delay in ADHD in brain regions important for the control of action and attention,” Philip Shaw, of the National Institute of Mental Health, said in a statement.

Shaw’s findings might encourage scientists to search for the root of this delay and a possible  genetic link that controls the timing of brain development.

The research also begs other questions; if ADHD is simply a developmental delay, then why do approximately 65% to 75% of all children carry it into adulthood? Either, it’s not solely a developmental delay or the developmental delay affects long-term brain function. The possibility exists too that it is not a developmental delay at all, but a different brain structure.  In the meantime, what is one to do? We suggest strengthening the brain you have. Maximize your capacity. Optimize your life: www.playattention.com.

More information: The article is “Development of Cortical Surface Area and Gyrification in Attention-Deficit/Hyperactivity Disorder” by Philip Shaw, Meaghan Malek, Bethany Watson, Wendy Sharp, Alan Evans, and Deanna Greenstein ( doi: 10.1016/j.biopsych.2012.01.031 ). The article appears in Biological Psychiatry, Volume 72, Issue 3 (August 1, 2012).

Print Friendly Print Get a PDF version of this webpage PDF

Are Some Teens Prewired for Addiction?

Posted by on May 14th, 2012 | No Comments

Researchers gain new insight on the ADHD connection

Robert Whelan and Hugh Garavan of the University of  Vermont  and  a  cohort of international researchers produced the largest imaging study of the human brain ever conducted. The researchers scanned the brains of 1,896 14-year-olds and discovered a number of previously unknown networks that go a long way to understanding addiction.

Their report published in the journal Nature Neuroscience (online April 29, 2012) helps answer whether particular brain patterns are caused by drug use or established before drug use. Professors Whelan and Garavan found that certain networks in some teenagers cause a higher risk for experimentation with drugs and alcohol – simply because their brains are wired differently making the teens more impulsive.

“The differences in these networks seem to precede drug use,” says Garavan, Whelan’s colleague in UVM’s psychiatry department, who also served as the principal investigator of the Irish component of a large European research project, called IMAGEN.  IMAGEN is a new study funded by the European Union that is conducting a systematic neural, genetic and behavioral assessment of teenagers in Ireland,England,France, an d Germany.

The significance of their work is the discovery that different brain networks appear to be involved in the impulsivity problems of substance abuse among teenagers than those with ADHD. Up to now, substance abuse was thought to be the same impulse control network associated with ADHD.

“The behavior might look the same but there may be different brain regions contributing to that behavior,” says Dr. Robert Whelan.

The researchers focused on the orbitofrontal cortex, a network commonly associated with impulse control. Diminished activity in this network can be associated with experimentation with all the vices: marijuana, alcohol, cigarettes and other illegal drugs in early adolescence. While sexual experimentation was not included in this study, research in this area would also be insightful.

“These networks are not working as well for some kids as for others,” says Whelan, making them more impulsive.

A teenager exposed to peer pressure regarding smoking a joint or drinking alcohol, provided parental  boundaries and structure have been set, would refuse the offer while the teenager with lesser orbitofrontal control would likely say, “Yeah, gimme, gimme, gimme!” says Garavan, “and this other kid is saying, ‘no, I’m not going to do that.’”

The researchers used a brain imaging technique called functional magnetic resonance imaging (fMRI). fMRI uses blood flow to indicate brain neural activation and network use. A complex computer algorithm assesses the blood flow and depicts the part of the brain being used by lighting it up on a computer monitor simulation. Whelan says that the researchers have distinguished seven different networks associated with impulse control.  The networks appear to be different among substance abusers and ADHD. Therefore, it is possible that the risk of ADHD is not necessarily a full-blown risk for drug use as some recent studies suggest.

“The take-home message is that impulsivity can be decomposed, broken down into different brain regions,” says Garavan, “and the functioning of one region is related to ADHD symptoms, while the functioning of other regions is related to drug use.”

Some caveats: fMRI imaging relies on complex computer algorithms and a certain amount of subjective analysis of the data presented. And while the research population was large (1896 teenagers), the researchers were actually measuring blood flow in the brain that is thought to be associated with neural activation in varying regions of the brain. In other words, given the limitations of nascent fMRI technology, this method is like using an Etch a Sketch to paint the Mona Lisa; it provides merely a rough outline due to its limitations.

So, is it a step in the right direction? Yes. Is it still a bit crude in detail of the actual neurobiology involved? Yes. Were parental or environmental factors examined? No.

My greatest concern with research like this is what one might do with the results albeit preliminary. Do we actually teach skills to adjust for impulsivity or do we simply offer another pill?

The fMRI is a crystal ball that cannot read the future of an individual. We still need to take control of our lives and shape our brains, not necessarily be just an end product of our genetics and conditioning.

Print Friendly Print Get a PDF version of this webpage PDF

Is ADHD Simply a Developmental Delay?

Posted by on December 8th, 2009 | Comments off

Attention-deficit hyperactivity disorder (ADHD) is conservatively estimated to affect anywhere between 5-7% of the world’s school-children. Is it possible that ADHD is the result of a brain that just develops slower than the brain of a child that doesn’t have ADHD?

Research has shown that the ADHD brain may develop differently than one without ADHD. However, no conclusive pathology (diseased or damaged location in the brain) exists; we don’t know what causes it.

What we do know: As a child’s brain develops, his experiences and environment help shape the connections in the brain. This development is also connected to genetic endowment. Thus, the brain develops dependent upon a complex interplay between nature (genetic endowment) and nurture (experience/environment). These connections form networks which help us process language, calculate math, feel, see, smell, think, and all else the brain is responsible to perform.

The part of the brain that is crucial to a child’s development is the cerebral cortex, the brain’s outer layer. The brain’s most complex functions like attention, consciousness, memory, and language are believed to be regulated in the cerebral cortex. As a child develops, gains experiences, and is subjected to his/her environment, the connections between the neurons (nerve cells in the brain) increase causing the cortex to thicken. The brain acts much like a muscle during adolescence; it’s a use it or lose it proposition. Connections which are frequently used are strengthened while unused connections are pruned away.

Researchers Philip Shaw, Judith Rapaport and others from the National Institute of Mental Health have proposed that ADHD may be the result of  lagging brain development resulting in an average 3 year delay. This theory is supported by earlier studies which found that children with ADHD have similar brain activity to slightly younger children without the condition.

Shaw and Rapaport used MRI (magnetic resonance imaging) to measure the brains of 447 children of different ages. They frequently noticed that the volume of the brain in the prefrontal cortex was thinner in ADHD children than other children of the same age. The cortex developed correctly over time, but the ADHD brain’s  development lagged behind about 3 years before it reached maturity. Among other things, the prefrontal cortex has the responsibility of governing attention, short-term memory,  and controlling inappropriate thoughts and actions. The researchers theorized that ADHD is a lack of control over these tasks, so it was logical to suggest that ADHD is a matter of developmental delay.

Significantly, Shaw and Rapaport found that the primary motor cortex developed faster in ADHD children. As its name implies, the motor cortex helps to plan and control movements. Shaw theorized that this might explain the restlessness, fidgeting and uncontrolled hyperactivity found in ADHD children.

This research raises more questions than it answers. Currently, the cause of the delay is unknown.  If ADHD is just a developmental delay, why do approximately 70% to 80% of children carry their ADHD traits into adulthood? This fact does not rule out Shaw’s conclusions, just that developmental delay may only be present in a minority of children labeled ADHD. Other children, the 70% to 80% previously mentioned, do carry their brain differences into adulthood.

Other research points to a set of genes responsible for the ADHD trait. If either genes and/or developmental delay are the cause, then what is one to do? The brain is an incredibly flexible organ. It is shaped by a variety of factors which means that parents, teachers, and other professionals can influence outcomes. Finding a program that addresses the needs of an ADHD child, helps shape behavior, and optimizes their potential is still the best practice.

Print Friendly Print Get a PDF version of this webpage PDF