The exact causes of adult ADD are unknown. ADD was once looked upon as a discipline and behavioral problem resulting from bad parenting. Some suggested it was caused by high sugar intake, food additives, excessive TV viewing, and family problems. However, none of these explanations is supported by scientific evidence.
Most scientists agree that ADD (whether in adults or children) is a biologically based disorder of the nervous system. Brain imaging research using a technique called magnetic resonance imaging (MRI) has shown that differences exist between the brains of children with the condition and those without, but the exact mechanism of brain function causing the symptoms is unknown. Scientists caution that MRIs used in studies are research tools and cannot be used to diagnose ADD in a specific person.
Recently published research suggests that ADD tends to run in families. In these studies, children with the condition have, on average, at least one close relative with ADD. Over the years, other theories have suggested that other factors -- such as exposure to lead in the environment, premature birth, birth trauma, and brain injury -- may lead to the development of ADD.
At times, everyone has trouble sitting still, problems with managing time, or difficulty completing a task. The behavior of people with adult ADD, however, goes beyond occasional fidgeting, disorganization, and procrastination. For them, performing tasks can be so hard that it interferes with their ability to function at work, home, school, and in social settings.
A diagnostic manual compiled by the American Psychiatric Association identifies three types of ADD:
A person with inattentive adult ADD has trouble focusing on activities, organizing and finishing tasks, and following instructions.
Hyperactive and impulsive adults feel restless, are constantly "on the go," and try to perform multiple tasks at once. They are often perceived as not thinking before they act or speak.
Individuals with the combined form of adult ADD show symptoms of both inattention and hyperactivity-impulsivity.