Three Main Types of ADD
Nearly every definition of attention deficit disorder identifies three main types of ADD: predominantly inattentive, predominantly hyperactive-impulsive, and both inattentive and hyperactive-impulsive.
Inattentiveness is identified by characteristics such as:
- Easy distractibility (particularly by stimuli which are unrelated to a task being performed).
- Difficulty with focusing on details and particulars.
- High frequency of mistakes which can be attributed to carelessness.
- Chronic forgetfulness.
- Inability to complete or follow through with tasks.
Hyperactivity-impulsivity is often associated with traits like:
- Being excessively fidgety.
- An inability to sit still for long periods of time.
- Difficulty with quiet, individual and non-active tasks.
- General impatience.
- Lack of behavioral and emotional inhibition.
A Diagnostic Definition of Attention Deficit Disorder
The DSM-IV outlines a total of 18 criteria for diagnosing ADD. (Although most lay people and indeed many professionals refer to the disorder as ADD, it is in fact officially known as ADHD, but this is not universally accepted).
There are nine criteria which identify the predominantly inattentive type (1A) and nine separate criteria for the predominantly hyperactive-impulsive type (1B). To be diagnosed with the disorder, a patient must demonstrate either at least six of the nine criteria for inattentiveness or six of the criteria for hyperactivity-impulsivity. If the patient demonstrates at least six of the criteria from both subtypes, then they are identified as having both inattentive and hyperactive-impulsive types.
Using these diagnostic criteria, it is possible to formulate a definition of attention deficit disorder which identifies it as the state of meeting the necessary requirements to be diagnosed with the condition. Put differently, attention deficit disorder can be defined as the collection of symptoms which are used for diagnosing an individual.
(It is important to point out that there are also criteria which require the symptoms to be present for a certain period of time and to significantly impair the individual, and they must not be caused by other mental health conditions).
Defining Attention Deficit Disorder as a Cognitive Impairment Syndrome
Most definitions of ADD classify it as a neurobehavioral disorder. This makes sense, as all of the diagnostic criteria used for identifying ADD are observable behaviors which are presumably caused by certain neurological configurations.
Yale clinician Dr. Thomas E. Brown has used his experience researching and treating ADD to develop a new model for attention deficit disorder. This is based on understanding ADD as "developmentally impaired executive function." Brown identifies six clusters of interrelated cognitive functions which are typically found to be impaired in individuals who are diagnosed with ADD: activation, focus, effort, emotion, memory and action. These capacities work together to perform executive functions such as regulating, directing and sustaining attention.
Brown refers to the impairment of these functions as ADD syndrome, rather than attention deficit hyperactivity disorder. This is because when some of these functions are chronically impaired in an individual, it can reliably be expected that impairments in the other capacities will also be found. Another reason is that all of these functions tend to respond in a similar way to treatment, suggesting that they result from the same underlying cause. His model of impaired executive function suggests that the label "attention deficiency hyperactivity disorder" may be misleading and might possibly mask certain aspects of the condition.
Problems with Defining Attention Deficit Disorder
Despite the growing consensus within the clinical psychology community that the current standard of diagnosis can effectively identify individuals who stand to benefit from treatments for ADD, there is no universally accepted definition of attention deficit disorder. Perhaps the main reason for this is our present lack of knowledge about how the brain works. While new technologies and methods for studying the central nervous system have been rapidly increasing in sophistication throughout the last several decades, there remains much that is unknown about exactly how the brain functions. This is particularly true at the higher cognitive levels.
It may not be until scientists come to a better understanding of how cognitive systems work that we will have a precise and commonly accepted definition of attention deficit disorder. Current research strongly suggests that one of the main causes of ADD is a heritable deficiency in how the neurotransmitters dopamine and norepinephrine are produced and released.
If this is indeed the case and the relevant details are discovered, attention deficit disorder may come to be defined as the mutation of a particular gene which is associated with dopamine or norepinephrine and causes the symptoms we now identify with ADD. Until then, perhaps the best definition of attention deficit disorder is the more uncertain and imprecise one which is based on the commonly accepted diagnostic criteria.
Sternberg, Robert J. Cognitive Psychology: Fourth Edition. Thomson Wadsworth, 2006.
Brown, Thomas E. Attention Deficit Disorder: The Unfocused Mind in Children and Adults. Yale University Press, 2005.