In training years ago, I learned that the street drug, Ecstasy, which was not very addictive, had a very long lasting, (years), affect on the individuals pleasure tolerance.

Simple things, like getting a new car, comedy on tv, sex, would no longer produce a pleasure response from the individual. Only that same drug can reproduce those feelings.

Since it was very popular, yet disappeared from the streets, my guess is the experiment was completed & Millennials were the test group.

So it would suggest that many who experienced this drug, and it being mostly gone from the availability, that there are many people still who have yet to get back in touch with their real emotions and feelings without the drug? You said it takes years, do we have a time frame?