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ADHD and Its Neurobiological Origin

ADHDAttention deficit hyperactivity disorder (ADHD) is a growing problem in the United States.[1] The American Psychological Association (APA) first added the condition to its diagnostic manual, the Diagnostic and Statistical Manual (DSM), in the late 1980s.1 The latest edition of the DSM states that approximately five percent of American children have ADHD; however, research indicates that the number is actually much higher.1 In fact, one study found that approximately 11 percent of youth between the ages of four and 17 suffer from ADHD.1 Over the past few decades, the rate of diagnosis has risen significantly, increasing at an average of three percent per year from 1997 to 2006 and five percent per year from 2007 to 2011.1

There are many potential reasons for the rise in diagnosis.1 It could be that awareness and understanding of the disorder has led medical professionals and educators to recognize the symptoms in more children.1 It could be that the modern way of life—complete with increased sedentariness, an unhealthy diet high in sugar, a decreased time period for recess and other physical education in school, and an increase in video games and other media—is to blame.1 Others believe that medical professionals over-diagnose the condition, when some are simply exhibiting normal, age-appropriate behavior.1

However, while the average age of diagnosis is seven-years-old, ADHD does not only affect children. In fact, it often persists through adolescence and adulthood.1 Approximately 60 percent of children diagnosed with ADHD as children will continue to have symptoms as an adults.1 Only twenty percent of adults with ADHD have been diagnosed, and only a quarter of those diagnosed receive treatment.1

ADHD limits a person’s ability to succeed academically, socially, and professionally.1 If a person does not learn to adequately handle the symptoms—through medication, behavior modification, or other treatment methods—they may not learn how to overcome the problems associated with the disorder.1

Although some of the underlying neurobiological causes of ADHD have been discovered, a team from the French National Center for Scientific Research (CNRS), University of Strasbourg, and French Institute of Health and Medical Research (INSERM) have recently discovered a potential neurobiological origin of ADHD.1 Experiments with mice found that hyperstimulation of a cerebral structure, the superior colliculus, causes the same behavior problems seen in people with ADHD.1 Researchers report that they have found an accumulation of the neurotransmitter noradrenaline in this area, which proves that this chemical mediator has a role in attention disorders, too.1

For the study, researchers experimented on genetically altered mice with duplicated neuron projections between the superior colliculus and the retina.1 They compared the behaviors of different strains of genetically engineered mice and a control group in various behavioral tasks that required colliculus activity.1 The genetically modified mice had visual hyperstimulation and excess noradrenaline in the superior colliculus.1 Noradrenaline, also known as norepinephrine, acts as both a hormone and a neurotransmitter, and it is associated with the fight-or-flight reaction in the body.1 It also affects the mind’s ability to concentrate.1 Therefore, an imbalance is associated with behavioral changes, including those characteristic of ADHD.1

This study broadens the understanding of the causes of ADHD, possibly allowing for a wider treatment approach for the disorder.1



[1] Friedman, J. (2014). The Neurobiological Origin of ADHD. Psych Central. Retrieved on May 16, 2014, from http://psychcentral.com/lib/the-neurobiological-origin-of-adhd/00019390

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