Estimates vary, but it is believed that up to 80 per cent of those with ADHD also have a learning disability. In the LD population, it is estimated that 30 to 40 per cent also have ADHD, so clearly the conditions are highly related. One of the main links between these two diagnoses is the fact that attentional deficits themselves can be one of the underlying information processing difficulties that gives rise to academic problems. In other words, problems with attention can be so pronounced as to interfere with the acquisition of reading, writing, or mathematical skills.
Similar to LD, Attention Deficit/Hyperactivity Disorder cannot be readily diagnosed through medical technologies, despite the fact that the disorder is due to brain dysfunction. However, even though attention and concentration are clearly a cognitive skill, and can certainly be measured, they are in fact a multifaceted set of cognitive skills in their own right.
Furthermore, the seat of attention/concentration abilities resides in the forward most part of the brain known as the “frontal lobes”. The frontal lobes are complex and functions relating to them are extremely difficult to measure. The reason for this difficulty is that the frontal lobes play an integrative role, coordinating and synthesizing inputs and information which is being received by other areas of the brain. Through the attentional processes, the frontal lobes are responsible for sifting out irrelevant information such as distractions in the environment. The frontal lobes are also the part of the brain responsible for adaptation to one’s environment. When we are involved in routine behaviours and skills, the frontal lobes are not highly activated in general. Most cognitive/academic testing is therefore weak at testing the frontal lobes because: (1) Both the clinical interview and testing generally occur in a quiet, distraction-free environment; (2) Testing protocols are generally highly structured, reducing demand on the frontal lobes which would otherwise have to create the “structure”.
There are some tests which are specifically geared towards AD/HD and many of these are well validated. However, in the experience of some clinicians, many of these tests often seem to produce “false positives” and/or be more effective with children than adults, perhaps in part because over the years adults learn to manage their attentional difficulties, especially in quieter, more structured environments.
Most often, the diagnosis of ADHD is made clinically, particularly in adult populations. “Clinically” means the examiner considers the full history of the client, considers the client’s behaviours and presenting symptoms, considers observations throughout testing (perhaps with greater emphasis than test scores themselves), and uses subjective client questionnaires. Additionally, input may be sought from significant others, friends and even co-workers and/or employers. Other possible explanations for the attentional and/or hyperactivity symptoms are then considered and ruled out before arriving at a diagnosis of AD/HD.
By Dr. J. Douglas Salmon Jr.
From “The Role of Cognitive Assessments in the Workplace“ in Benchmarking: A Guide to Hiring and Managing Persons with Learning Disabilities, 2005, Adult Learning Disabilities Employment Resources, Toronto, ON.