Inner-Ear Disorders May Cause Hyperactivity
Inner-ear disorders are physical conditions that alter normal function in the innermost structures of the ear, which play an essential role in the ability to hear or maintain a sense of balance. Current evidence indicates that children diagnosed with behavioral problems develop serious inner-ear problems more often than their peers unaffected by behavioral problems. In a new study published in September 2013 in the journal Science, a multinational research team examined the potential connections between inner-ear disorders and childhood behavioral disorders. The members of this team concluded that inner-ear disorders may actually produce changes in brain function that contribute to children’s dysfunctional behaviors.
Inner-Ear Disorder Basics
The inner ear contains three vital structures, called the cochlea, auditory nerve and the vestibular system. Proper function inside the cochlea and auditory nerve gives you the ability to hear, while proper function inside the vestibular system gives you the ability to maintain your balance when you change the position of your head relative to your body and surroundings. A number of conditions or disorders can damage a person’s hearing or balance by altering function inside the inner ear, including such things as viruses, traumatic head injuries, high-decibel noise, migraine headaches, toxin exposure and an ailment called Meniere’s disease. In addition, some people develop hearing problems as part of the aging process. However, most severe inner-ear disorders have a genetic basis and pass from generation to generation.
Childhood Behavioral Disorder Basics
The three most prominent childhood behavioral disorders are oppositional defiant disorder, conduct disorder and attention-deficit/hyperactivity disorder (ADHD). Mental health professionals sometimes refer to these conditions together as externalizing disorders; in addition, oppositional defiant disorder and conduct disorder belong to a larger group of conditions called “disruptive, impulse-control and conduct disorders.” Children with oppositional defiant disorder have an unusually prominent tendency to do such things as argue with adults, exhibit strong resentment or anger, purposefully antagonize others or refuse to follow rules. Teens and younger children with conduct disorder act in unusually impulsive ways and participate in such relatively extreme conduct-related behaviors as flagrant rule breaking, aggressive actions toward others, arson or other forms of property destruction, animal cruelty, bullying, truancy or the use of weapons. Children with ADHD may exhibit unusual degrees of hyperactive and impulsive behavior, exhibit an unusual inability to maintain attention, or exhibit combined symptoms of hyperactivity/impulsivity and inattention.
Over the years, many researchers have noted that teenagers and younger children affected by behavioral problems tend to experience an unusually high rate of severe inner-ear disorders. However, no one knew what might explain this situation. In the study published in Science, a team of American and German researchers used laboratory experiments with mice to explore the underlying factors that could link inner-ear disorders to childhood behavioral problems. They decided to perform these experiments after noting that mice with severe hearing and balance problems frequently exhibit abnormally high levels of hyperactive behavior.
After examining the affected mice, the researchers concluded that the animals’ hearing- and balance-related problems stemmed from a mutation in a single gene that helps control normal function in the inner ear. This same gene performs the same function in humans. Through a series of additional experiments, the researchers established that the gene mutation found in mice triggered the onset of hyperactivity by changing the normal function of a part of the brain responsible for providing voluntary control over body movement. In short, the genetic changes involved in severe inner-ear disorders also contribute to poor body control and hyperactivity.
Since inner ear function in humans is controlled by the same gene that controls this function in mice, it’s highly possible that the same inner-ear disorders that lead to hyperactivity in mice also lead to hyperactivity in human beings. If this is true, then the presence of a severe inner-ear disorder in a child may directly contribute to the onset of behavioral problems by increasing that child’s normal level of hyperactivity. According to the authors of the study published in Science, future researchers may eventually develop medications that can ease inner-ear-related hyperactivity (and therefore decrease the impact of childhood behavioral problems) by reversing the brain effects of the genetic mutations that lead to inner-ear disorders. The study’s authors also believe that future research may uncover a connection between other forms of sensory impairment and increased chances of developing some sort of significant mental health problem.