My classmate says stimulant meds eventually started doing the opposite of what they used to

My classmate was telling me about his experience with ADHD medication and it honestly sounded frustrating. When he first started taking methylphenidate, it seemed like everything improved. Better focus, better grades, more motivation, improved emotional control, and a general feeling that life was finally becoming manageable.

The strange part is that he wasn’t taking unusually high amounts or chasing a buzz. He stayed within normal prescribed ranges and for quite a long time things worked exactly as intended. Then, little by little, the benefits started fading.

What bothers him now is that the medication no longer feels neutral when it doesn’t work. Instead, it seems to push him in the opposite direction. He describes feeling mentally slower, emotionally flat, foggy, tired, and less motivated than before. The same thing that once helped him feel engaged now seems to leave him disconnected and zombie-like.

He’s even tried stepping away from it for extended periods, hoping the original effects would come back. But whenever he revisits it, he often finds himself running into the same disappointing reaction almost immediately.

Has anyone else known someone whose stimulant medication seemed to “turn” on them over time like this? Did they ever figure out whether it was tolerance, changing life circumstances, stress, sleep, or something else entirely that made the experience so different from the beginning?