There's probably over diagnosis, but since ADHD medications are safe at low doses, there's not much downside with over diagnosis. On the other hand, there's 2-8% of the general population that has ADHD, and those individuals gain significant benefits from medication.
If you're unsure if ADHD really exists, it may be useful to read the genetic studies that show ADHD correlation with specific SNPs, and decide for yourself [1]. Personally, I find the evidence satisfactory.
That said, I personally believe that ADHD type symptoms could be caused by several different disorders. ADHD is kind of like bipolar disorder - it covers a lot of areas and is sort of a fallback category when other diagnosis don't fit.
If you're unsure if ADHD really exists, it may be useful to read the genetic studies that show ADHD correlation with specific SNPs, and decide for yourself [1]. Personally, I find the evidence satisfactory.
That said, I personally believe that ADHD type symptoms could be caused by several different disorders. ADHD is kind of like bipolar disorder - it covers a lot of areas and is sort of a fallback category when other diagnosis don't fit.
http://www.ncbi.nlm.nih.gov/pubmed/?term=ADHD,SNP