I have ADD and i used to take ritalin and then switched to dexedrine, but now I'm off stimulants because I think they are the devil.
I remember in elementary school not being able to sleep at night because of the ritalin, I lost a lot of weight, and it had a really negative effect on my personality. I have a personal theory about people who take stumulants for ADD that I share with some of my friends. In college, all the people that take meds for ADD (ie. are addicted to stimulants) seem to be on a much lower level mentally than people who dont, I think it makes it difficult for people to show their true personalities - its appears that these people have a false sense of motivation and happiness. Ive heard that stimulants actually slow your brain down, making it easier for your brain to process and organize information, and I think this takes a toll on a person's ability to be an individual and their creativity. People who take add meds over a long period of time seem to have what I like to call "adderall psychosis" where their everyday lives are a means to an end, instead of them being able to enjoy themselves.
If you havent noticed I'm on a personal crusade against the use of stimulants (especially for children), they almost ruined my life thank god I got off them. If taking adderal, ritalin, dex, whatever is not absolutely necessary for you I would urge you to get off them. I still have ADD but have learned to suck up and deal with it. The only thing you can do to conquer ADD is to make a conscious effort to organize your time. Of course, meds are necessary in extreme cases but I think ADD is one disorder that is rediculously overmedicated in america. So many kids are walking zombies cause of this shit, and i was one of them and I think it had a permanent effect on my personality and brain development. I mean look at it, your giving so many kids uppers that dont need em because thats the thing to do, oh, kids having trouble in school give him drugs, sure it'll make you pay attention but your throwing a bunch of dangerous chemicals into an undeveloped mind.
Regarding the use of cannabis and uppers, over the long term i think this can be much more detremental than either of the two on their own, once in a while its not bad. Again this is from personal experience and my observations of other people who combine these drugs consistently/