Caffeine is a stimulant drug used all over the world. First-line stimulants used for ADHD are in a similar class. They work quickly and the side effects are quickly apparent. Stopping them isn't a risk to your health. Overdosing to the point of severe injury is difficult.

Over-the-counter pain medications are more far more dangerous in all categories: allergies, overdose, effects of long-term use, etc.

Correlation does not equal causation.

Stimulants are one of the safest medications used. There is plenty of data to support this.