[HONEST_ANNIE]

Illegality increases harmful effects.

Methamphetamines were used legally long time before they became illegal. Paul Erdős was probably the most famous (amphetamine and methylphenidate) user. Using meth when studying was also common.

Methamphetamine derivatives have reentered the society in the form Adderall and other drugs.

[MadWombat]

> Methamphetamines were used legally long time before they became illegal

Methamphetamine was invented in 20th century. So "long time" is a few decades max.

[MagnumOpus]

Nitpick: Invented in the 19th century. Mass manufactured for OTC self-administration from 1921 onward. At least in Germany, available OTC for the next 70ish years. Became prescription-only in 1988, became banned from prescribing in 2008 -- i.e. it's been legal a lot longer than it's been illegal.