It seems that you have a few different things going on with your question. This said, I did not edit the question so as to examine the multiple issues as a whole (to insure the real message and concern is not lost).
ADHD (or Attention-Deficit/Hyperactivity Disorder) has been misunderstood for a long time. The DSM (or Diagnostic and Statistical Manual of Mental Disorders) identifies ADHD in three different ways: 1) ADHD-PI (Predominantly Inattentive); 2) ADHD, Predominantly Hyperactive-Impulsive Type; and 3) ADHD, Combined Type (where both PI and Impulsive Type exist comorbidly).
A paper on this subject will do multiple things. First, it will define all three types of ADHD. Second, it will discuss what ADHD looks like in a child. Lastly, it will discuss the effect of ADHD on a child. This section of the essay can be divided into numerous sections. First, the essay will define the medical effects of ADHD on a child. Second, the paper can define the effects of ADHD on a family. Lastly, the paper can define the effect of ADHD on the diagnosed child (this can include both private and public spheres of life).
Essentially, I do not think that your subject is too general. Instead, I think that you may not have a good idea of what the essay needs to discuss in order to define the topic well. Try constructing an outline which lays out what you wish to write about. If the outline begins to get too long, you may wish to narrow the material. Luckily, you can define the types of ADHD and discuss what ADHD looks like in your introduction. You can save the remainder for the body of the essay.