There have also been “unbelievers” who have fed on these difficulties to create controversy, misgivings, and fear. Nonetheless, by 1998 the scientific response to all of this controversy had created a body of research on ADHD that led the American Medical Association to call ADHD “one of the best-researched disorders in medicine, and the overall data on its validity is far more compelling than for many medical conditions.”11
Perhaps the most compelling of this data came from the research that demonstrated the clear genetic basis of ADHD. The strongest data comes from the ten twin studies that reported heritability between 0.6 and 0.9 (1.0 means a solely genetic pattern of transmission) across various sets of diagnostic criteria.12 Adoption and family studies (see review by Faraone and Biederman13) support the concept that there is little contribution from the environment. ADHD usually runs in families. Stressors and bad parenting can make the manifestations and impairments worse but they do not cause ADHD.
The evidence that ADHD is a brain-based developmental disorder has far-flung implications. Just as no other genetically based developmental disorder disappears with age, neither does ADHD. However it’s manifestations and the individual’s compensation to the disorder may change throughout the lifespan.14 The basic features, impairments, and treatments are very similar for both children and adults. People do not “outgrow” ADHD just as no one outgrows any other genetic disorder or any other developmental disorder. All people develop better abilities to pay attention and control impulses as they grow older. Most patients will benefit from lifelong medication even if they have “learned to cope with ADHD” because life stresses increase rather than diminish with age.
Our understanding of attention deficit hyperactivity disorder (ADHD) has progressed more in the past 10 years than in all the years since it was first described in 1902. We now have studies using magnetic resonance imaging (MRI), positron emission tomography (PET), and (SPECT) which provide us with some understanding of the functional anatomy of the human brain. Neuropsychiatric research has provided new insights into basic mental functions and processes. Until recently all research into ADHD was done on hyperactive boys leaving us in a complete void regarding girls, adults and those with problems with inattention. The ADHD picture has been enlarged by new studies giving us a more comprehensive understanding of the far ranging effects of this disorder.
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