Margaret V. Austin, Ph.D., edited by C. E. Zupanick, Psy.D.
Discoveries & Controversies in ADHD Research
Scientists conduct research to continuously increase and update our knowledge and understanding of physical and mental disorders. This research enables clinicians to rely on science to provide the most current and effective methods of evaluation, diagnosis, and treatment. As research proceeds, new controversies emerge. Future research will be needed to resolve these controversies. In this chapter, we will examine some the recent trends in research. Later, we discuss the various controversies surrounding ADHD.
ADHD: New and Exciting Brain Research
As we discussed in the first section, ADHD is a brain disorder. ADHD is usually first noticed during childhood. However, it may continue to pose challenges throughout a person's life. We also discussed several key symptoms of ADHD, including attention problems, impulsivity, hyperactivity, and problematic behaviors. Much of the research focuses on the identification of people with ADHD, and how they differ from people without ADHD.
The prevailing view is that ADHD is a brain disorder; present from a very early age. Nonetheless, identifying the early signs of ADHD remains challenging. This is because most children are first identified during late elementary or early middle school. This late identification limits the possibility of conducting meaningful research with very young children who have ADHD. In other words, we often don't know which children have the disorder until problematic behaviors become more evident. For this reason, most research on ADHD has been conducted with school-aged children. Therefore, a great deal more is known about this particular age group.
According to Lavigne et al. (1996), approximately 2% of pre-school children exhibit symptoms of ADHD. DuPaul et al. (2006) found ADHD symptoms are predictive of future academic and social skills problems. Although many people outgrow ADHD symptoms, such as hyperactivity, restlessness often remains, along with mood problems, lack of motivation, and an inability to sustain focus. Research strives to understand the exact origins of ADHD. This research is considered vital to expanding our understanding of ADHD.
Brain Differences in People With ADHD
Researchers have spent a great deal of time looking for differences in the brains of people with ADHD, compared to people without ADHD. They have found several areas of differences. The following is a summary of what we know so far.
One fascinating topic in ADHD research is that of biological markers. Biological markers help to identify the chemical and genetic differences in people with a disease or disorder. Scientists have demonstrated that ADHD is genetically heritable; meaning, it is passed down from one generation to the next. Therefore, it makes sense to wonder, what are the biological differences (specifically brain differences) between people with, and without ADHD?
Several research studies have found that differences in certain brain structures predict the severity of ADHD symptoms. One such brain structure is the amygdala. The amygdala is associated with memory, emotion, and aggression. A smaller amygdala was associated with more severe ADHD symptoms. Researchers have also found poor neural connections between the amygdala and the pre-frontal cortex. The pre-frontal cortex influences planning, sequencing, and strategic behaviors. Scientists speculate that this might account for problems with impulsivity; a primary ADHD symptom.
Researchers have studied both brain structures, and brain activity, in individuals with ADHD. These studies found that people with ADHD have brains that are about 4% smaller than average. The two brain areas most affected by the size reduction are the prefrontal cortex, and the anterior temporal areas. These smaller brain areas might account for several ADHD symptoms. The pre-frontal cortex is associated with self-awareness and the ability to self-regulate emotion and behavior. These are challenging areas for many people with ADHD. Damage to the pre-frontal region can cause increased impulsivity, anger, and hyperactive behavior. The anterior temporal areas of the brain affect hearing and language skills. This includes the ability to interpret language and non-language sounds; and, to understand verbal communication. Decreased brain size in this region could also influence memory and learning. Once again, these are skills that seem attenuated in people with ADHD.