Im sure eventually whatever pills the Germans were taking back then were bad for you but I would imagine smoking huge doses of not so pure street meth is quite a bit different than something created in a lab.
That being said if anyone uses drugs to avoid sleeping for many days straight I would imagine it's quite horrible for your mental health
So…not that different.
Considering the soldiers were already extremely high risk for lead poisoning, might have been low on the list of concerns.