I'm generally trusting of pharma studies. But a bout with Zyrtec has convinced me that psychological effects aren't always well studied, even for common drugs.
I'm convinced that prolonged use of Zyrtec makes me angrier for example. I've experimented with my allergies, and when I'm off Zyrtec, I'm sniffling and sneezing all the time... But generally happier and healthier from a mental perspective.
Every medication you take, especially with prolonged use, should be considered an experiment IMO. Even if the studies are show safety and efficacy... there are plenty of other side effects that could diminish quality of life.
Allegra doesn't have this problem for me, so I just switched to that.
Fatigue is a common side effect of Zyrtec (and other antihistamines). From purely anecdotal evidence, I think most people have to experiment with allergy medication to find one that works best for them. I know that I'm dysfunctional when taking Zyrtec but Claritin doesn't bother me at all.
I definitely had to experiment as well - I bounced around between Claritin and Allegra for a couple of years. I did try Zyrtec and experienced significant fatigue with it, which led me to stop using it pretty quickly.
Earlier this year I discovered Xyzal (expensive, but does have generic versions, too), which appears to be a close relative to Zyrtec. Interestingly though, they recommend taking it at bedtime rather that in the morning, the idea being you'll get a better night's sleep from not being congested AND you'll sleep through the worst part of the fatigue from it. This has worked out well for me - my allergies have bothered me less this year than they have in the last ten years or so, and I sleep better at night (I've had problems with insomnia off and on for ~20 years).
RE: the OP, I'm in my mid 40s and have always had some issues with following through and not procrastinating, and my sister was recently diagnosed with ADHD, so it's probably something I should at least discuss with my doctor at my next physical.
Don't they prescribe Adderall for ADHD? It's a mix of amphetamine salts. Same with Dexedrine. Same with Zenzedi.
Other stuff like Ritalin is also potent stimulant - like probably all ADHD medications - with withrawal symptoms ie. suicidal thoughts, depression and other mental and mood changes etc. It's serious shit.
Pure FUD.
ADHD meds, taken in prescribed doses, have been proven in studies to not have negative impacts on either your cardiovascular system or your brain.