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.