What is Attention Deficit/Hyperactivity Disorders (ADD, ADHD) and what causes it?

What is it? difficulties associated with it?
Explanations / Theories?- causes.
the lectures and reading provided is a guide and indication, you should conduct your own literature research. read through information provided such as criteria which shows what you need to do for a first, like insight into some current issues and providing strengths and limitations in different kinds of evidence. back up points with literature.