ADHD and Ritalin treatment: This is a well-known controversy about the frequency of the use of the drug Ritalin for treatment of behavior disorders such as Attention Deficit Hyperactivity Disorder (ADHD). There is a strong tendency for doctors to diagnose a child as ADHD, when in fact there may be other behavioral problems, or even nothing wrong with the child beyond merely normal childhood or teenage behavior. Because it is a behavioral disorder, ADHD is inherently difficult to diagnose. Part of the problem is that parents and teachers have been pressing for the particular drug, even before any attempt at medical diagnosis is made.
Irritable Bowel Syndrome (IBS): The attention to IBS, particularly in the USA, has led to it being frequently the diagnosis for chronic digestive disorders. Certainly, there is a lot of IBS in the population, but this tendency has meant other causes of chronic digestive problems such as Celiac disease and Crohn's disease to get overlooked.
Middle ear infection (acute otitis media) in children: Middle ear infection is often over-diagnosed in infants and young children. There are various causes of redness of the ear membranes other than otitis media, but there is a tendency of doctors to diagnose otitis media and start a course of antibiotics, sometimes needlessly.
Sinusitis: It is common for sinusitis to be over-diagnosed. Some studies have shown that many of those diagnosed with the condition do not have it at all. Various other conditions such as common cold, flu, and asthma can lead to some level of sinus passage inflammation, that does not necessarily warrant a full diagnosis as sinusitis.
Lyme disease: Some sources claim that Lyme disease is now becoming over-diagnosed rather than under-diagnosed, because it is now more well-known than in the past, but is a diagnosis that is difficult to confirm because of non-specific symptoms and a lack of definitive tests.
Alzheimer's disease: As the most well-known cause of mental deterioration in older people, Alzheimer's disease is over-diagnosed and various other alternatives are overlooked.