The stimulants can, especially in the early days, affect your mood. A good MD will work carefully to start very slowly and ramp up, with the idea to give you the lowest possible effective dose.

For example:
my MD started me on the lowest dose of ritalin once a day for a week

then twice a day for a week

then once that was ok I was given a longer acting version called Concerta that I took once a day.

it took six months to ramp me up to my current dose. there were times he felt it was time to go up and I wasn't ready. there were times when I felt it was time and he wanted me to wait. I had some side effects that went away if I went down a dose level, and then as I adapted, I'd move back up again. My dr. was very experienced and warned me about what to expect--a period of feeling invincible for a few months that would fade (true), and a feeling in the evenings of "rebound" as medicine faded (true). He was my rock when I started on this and still is It brings tears to my eyes how he helped me change my life. Now I only see him every three months for 30 mins and I'm given an unusual amount of latitude: I'm given various doses and allowed to manage it myself--choosing lower doses when I want to drink real coffee (my full dose does NOT work with caffeine) or when I can't get a full night's sleep. I'm told this is highly unusual given the meds are a controlled substance and a sign of the faith my MD has that I'm not a drug seeker. (he's right. I saw "requiem for a dream" and let's say he'll never have to worry...)

I was lucky. I can afford the best doctors. the right medicine worked, the first time. This is not true of everyone.

I cannot emphasize enough how important it is that anyone who thinks they have ADHD to go to an MD who specializes in this stuff. Family doctors do NOT count. your basic Ph.D therapist doesn't count.

start with science, go slow and built outwards. FWIW my therapist says he will only work with 4 MD's in SF because his take is that they're all pill pushers. My MD is one of the only MDs in SF allowed to provide telephone prescriptions for Concerta. The pharmacy he sends me to never has shortages. This is also not consistently true, even in SF.

It's no joke. Amphetamines can screw you up. Take this stuff seriously, please and find a good doctor for a proper evaluation.

edit to add: you know I have ADHD: I didn't answer your question. haha!

the short answer is that yes, in the beginning your mood may be "up" and you may feel down on the rebound while you are adjusting. But as you stay with it, things even out and become VERY predictable. If you have ADHD you will recognize the terror I used to have about making sure my brain was ON a the right time--all sorts of weird rituals to wake it up for an important meeting, etc. On the meds, I have confidence my brain will be at its level best so my anxiety and its attendant grouchiness just went away. PS: coaching and therapy (two different things) helped this a lot and if you're late diagnosed as I was, you will need them. I recommend reading "driven to distraction" before you start meds, because that "invincible" feeling the first few months is the best time to start changing habits. you will dip in motivation after that, but never as bad as without and having those systems in place to fall back on will save you.