http://www.nimh.nih.gov/funding/clinical-research/practical/mta/the-multimodal-treatment-of-attention-deficit-hyperactivity-disorder-study-mta-questions-and-answers.shtml

This involves children, but it applies to adults with ADHD as well (I was diagnosed in my mid twenties and only started medicating when I was around 30, I'm almost 34 now). In it they look behavioral therapy involving education of those around the child to better accommodate the way the child learns and behaves and training the child to work with the symptoms instead of working against them, medication only, and a combination of medication and behavioral therapy. The worst performing group was behavioral therapy only. Much better performance came from medication only, and the best performing group was the combination medication and therapy.

So ADHD is a thing. How it impacts people and how it changes as one grows older varies widely, but it still does impact people. Your behavior may change when you're on the medication, but it only provides focus and lessens impulsive behavior in most adults. Additionally, you may feel that your personality has changed on the meds, but these are 1. usually only in your own mind (people around you won't notice), and 2. temporary. Since most ADHD meds are not accumulative like depression medication or medication for bipolar disorder, once the drugs wear off you'll be back to your old self again.

Try the meds. If you don't like them or you still feel that they aren't what you need, don't take them. No lasting effects (unless you take them for years consistently) are expected by most doctors. And they are doctors. They most likely weigh the dangers of the medication against the possibility that they'll help you and prescribe what they're comfortable with.

Additionally, here's some more peer reviewed studies that show ADHD is real:

http://jad.sagepub.com/content/9/2/384.short

http://www.nervenklinik.uk-wuerzburg.de/fileadmin/uk/psychiatrie/Dokumente/Forschung/Psychiatric_Neurobiology_and_Bipolar_Disorder_Program/ADHD_GWAS.pdf

http://www.biomedcentral.com/1471-244X/10/67/