Researchers have long searched for answers as to the underlying causes of the various ADHD symptoms. One possible answer that has been put forward is that of the low arousal theory. This theory maintains that people with ADHD have abnormally low arousal levels, which means that they seek external stimulation in order to keep themselves as aroused as possible.
In order to understand this, imagine for a minute that you are falling asleep in the middle of an important meeting or class. To keep yourself awake, you might feel the need to stand up and walk around, take a drink of water, or start a conversation with the person next to you. People with ADHD feel the same way when forced to sit still and concentrate on something that does not interest them. Their impulsive behavior is simply a reaction to the lack of stimulation and arousal that they feel.
There is some evidence that seems to support this claim. For example, Ronald D. Chervin, a Professor of Neurology at Michigan University found a strong relationship between hyperactive behavior and daytime sleepiness or nighttime sleep deprivation. In light of low arousal theory, his results make sense: arousal problems can lead to sleep problems. Although still only a theory, it does appear to answer several questions about ADHD.
Inattentiveness and Impulsiveness
When people first learn about ADHD, they may wonder why inattentiveness and impulsiveness are both symptoms of ADHD. How are these two characteristics connected? You can understand the answer to this question by explaining that if someone does not pay much attention to the environment, they may act impulsively because they have not thought things through enough. With the arousal theory in mind, however, there is another way to explain this. The inattentiveness may be due to the fact that there is not enough stimulation in the environment to hold their interest. Once people with ADHD experience the inattentiveness, they struggle to stay attentive by acting impulsively in order to increase their stimulation.
Focused or Unfocused?
Many parents of children with ADHD have pointed out a paradox in their children. They wonder how children with ADHD can focus so intently on television or video games (and adults with ADHD can focus intently on their interests), but they cannot focus on mundane chores or homework.
If you examine that behavior from the perspective of low arousal, the activities that people with ADHD find highly interesting are stimulating to them, and therefore their state of low arousal does not cause them to seek additional stimulation. Activities that are of low interest leave them feeling like they need more stimulation and they will either daydream due to lack of stimulation or act impulsively in order to stimulate themselves.
The Use of Stimulants
The low arousal theory also explains why stimulants, which usually increase spontaneous motor activity, are typically the medication of choice for people with ADHD who are already hyperactive. When people take stimulants, they have increased arousal, which means they are getting more stimulation from situations around them. Therefore, when people with ADHD take stimulants, they no longer have the need to act impulsively in order to add stimulation, and they can sit and focus more intently on whatever they are doing. In short, the stimulants give them the arousal they are seeking.
The theory of low arousal in ADHD children and adults provides an interesting perspective on what may be at the root of behaviors and behavior modifications that can sometimes seem perplexing.
Johnson, Addie and Robert W. Proctor. Attention: Theory and Practice.
Incredible Horizons. "Info on Understanding ADD\ADHD." https://www.incrediblehorizons.com/Understanding%20Add.htm
Science Stage. "Group: Low Arousal Theory." https://sciencestage.com/g/3912072/low-arousal-theory.html