My parents know that I 'was' into drugs, the only thing they don't know about is that I've taken heroin. I've had a bit of personal shit going on the last two years, I had to move back with the folks (I'm 34), started abusing benzos pretty bad and was walking about like a zombie for awhile. It all came out around about that time, I had a 'moment of despair'.
Now they are always watching.
Friends know because they were always taking with me. Girlfriend knows, she doesn't abuse anything.
I'm not open to strangers at all, or work colleagues. There has to be a 'nudge nudge, wink wink' conversation before I open up, drugs are generally still too taboo in the UK.