It was an intersting program, and it really showed a completely different lifestyle.  I'd like to think in the same situation I wouldn't fall into drug use, but you never know do you?
I got the impression a lot of the addicts were trying to escape depression or their poorer lifestyle though Crystal Meth.  But it's such an addactive drug it gets them into a worse position, which is really saddening  :(
Indeed :   the phenomena of 'self medicating' is all too common, if the individual(s) concerned do not seek an official intervention for a building mental health health issue, be it reactive or indigenous.  I have an old mate that used to work for Manchester Mental Health / Social services, and he confirmed that in addition to the above - there were people with genetically hard wired addictive personalities, who would then get sucked right into a lifestyle that originally 
may have begun due to self medicating.  Without taking any moral stance on the issue, he noted that some would get addicted to almost anything , whereas others could do a bit of what they fancied and leave it alone at will.  The phenomena embracing anything from coffee, sex, spending and of course B.K.P ! 
We 
do have free will however - and ( speaking as the partially dammed ) the first step to redemption / a healthier lifestyle - is still being willing to take total responsibility for one's life and actions, or accept that ( beyond pubescent experimentation and freedoms )  our every adult decision dictates our eventual fates.