Are ADD and ADHD real diseases?

I was just wondering because in 7th grade my parents brought me to a psychietrist (spelling) because I was making bad grades. Basicly I wasn't turning in my homework at all and was making 100's for tests so I was making overall 70's. Well the psychietrist told my parents that I had a problem and needed heavy medication. Ofcoarse my parents are good people so they said thank you for your time and just left. Now I am a junior in high school and make high 80's and low 90's. So now I believe that those diseases aren't real and are just a cause of bad parenting and nothing hereditary. I have even taken ADHD pills and all they did was make me irritable and angry.