ADHD is one of the most controversial topics in modern medicine, and for good reason. If the medical community hasn't come to a conclusion about this, it's very unlikely we will, but for the sake of the argument I will say "sometimes."
ADHD is overdiagnosed and has contributed to the decline of the field of psychiatry in the eyes of the public. As an aspiring physician I have to say I'm not even considering psychiatry, and this is partly because of the corruption in the field. ADHD is the go-to disease when a doctor can't figure out what is wrong, or when they want to make a quick dollar. The symptoms of ADHD can be easily attributed to many other things, such as an unhealthy diet (high sugar can do terrible things to a child), an ineffective approach at teaching, or just plain old bad parenting, which we so often overlook. I believe ADHD should be diagnosed and treated only in severe cases after it has been proven that external factors are not to blame.