Answering this question gets a little old after awhile. Part of the problem, of course, is that there are now, and have been in the past, those who use attention deficit hyperactivity disorder in one way or another to further their own selfish ends. Some of those people come from the ADHD is real side, and some of those people come from the ADHD is fake side. Of course, there are many self-serving types in between as well.
To answer the question whether ADHD is real or not, one needs to consider numerous factors. First and foremost is the fact that the current scientific understanding of how the brain functions, brain biology, and mental health has grown exponentially in just the last 30 years. That being said, our comprehension of how the brain works is staggeringly low. Even the scientific techniques we currently use to study the brain are crude. In many cases the science behind much brain research starts out with a laughably simple assumption that may or may not be true.
Consider, for example, PET scans. A PET scan is a way of measuring how the brain works. In many recent ADHD studies, PET scans have been used to show that adults with ADHD and children with ADHD have brains that function differently from brains in subjects without ADHD. That is biological proof that ADHD is real, right?
Unfortunately, the whole concept of the PET scan is based upon an unproven assumption.
PET scans don’t actually show how the brain works. They don’t measure which parts of the brain are working, nor do they give any insight into the complex inner relationships between various regions of the brain. What PET scans measure is how much glucose is being used by the different parts of the brain. The assumption is that since glucose is the body’s energy source, the tissues in the brain using the most glucose must be working the hardest. The next assumption is that if any particular brain tissue is working hard, then it must be doing something at that moment. Thus, the areas in a PET scan that glow brightly are the regions of the brain being most heavily used during that time.
These assumptions have been backed up a bit via the other main source of brain research, which is far more crude. Much of what we know about the brain comes from studying brain injuries and brain damage. If a person has an accident that destroys a certain area of the brain, and then can no longer speak, one can draw the conclusion that the damaged region is responsible for speech. PET scans show the same areas glowing brightly when a person is talking. That hardly counts as proof, but it does mean that the current assumptions under which we use PET scans are at least reasonably good ones.
So, is ADD real?
Even PET scans are inconclusive. While ADHD brain scans have consistently shown different activity in brains of subjects with attention deficit disorder, they also show a wide variety among people without any diagnosed conditions. One could make the claim that a PET scan of a Type-A person would look differently than a scan of lazy person. That opens a whole can of worms.
For now, what we can say definitively about whether ADHD exists is that there is a large sub-population of people who have similar issues and that these issues tend to respond in similar ways to specific treatments. That in and of itself is good enough for a start. After that, as seems to always be the case, more ADHD research is needed.