Nyspunjabiji,
No one is a drug addict per se.. or an alcholic, or a gambler, or a womaniser, these are all states of minds that We hide to when our real life is either objectionable to us, repulses us. These are all forms of escapism and your son is addicted to these feelings of escapism. The key here is to find out why he feels the need to escape from his life, there are many reasons for this, some that I can think of
Frustration with religion, you say you are a very religious Sikh family, this is not quite the same as a very enlightened family, would you say the primary focus is on tradition and rituals, rather than understanding and enlightenment? If so, your son may be frustrated at being made to do things he does not understand, in my opinion, some education about his background might be an idea, a family day out at an exhibition of Sikh art, or getting a film on Sikh history, awaken in him his background, give him some Sikh hereos to admire, maybe encourage him to read books, all for no other reason than to get him to realise that the men and women that died before him, died for a reason, they had a purpose in life that was bigger than getting stoned or drunk, I can guarantee that he his not enjoying what he is doing, his mind is lost, but very slowly use our history, the meaning of why we are here to at least try and open his mind a bit.
Maturity, at this age, he wants to be treated like a man, he wants to be a man, but it is an 18 year olds vision of what is a man, and at that age, men do what they want to do, and they rebel, so how much of this is natural rebellion, and what can you do about it, it depends on how you treat him, treat him like a loser, he will get worse, he will try and be the best loser he can be, so this is a dangerous road, remember, the objective is to try and get your son back on an even keel, not get him to what you want him to do, I would praise everything he does that is good, and try overlook the bad, in the hope that the bad lessens and lessens, there is no magic button to press to get rid of the bad, you just have to work on the good, sure he will let you down, sure he will mess up, but if you can be patient with him, and if he can be gracious, and realise that your love for him is allowing you to overlook certain facets of his life while he 'sorts himself out', then keep pushing our Culture, our history, praise him, give him lowly responsibilities, and very very slowly give him back his soul, ask him to read and understand and even try and live Mool Mantra, explain to him that fear is bourne out of wrong, and if one does no wrong, then one will not feel fear, in time he will come to peace with drink and drugs, maybe he will loose interest all together, but more than anything he now needs you and your husband as his best friends, two people he can be completely honest with, and you have to be strong and slowly wean him off this lifestyle by trying to fill his life with alternatives, but you cannot afford the luxury of a big shouting session if he fails, more than anything his success cannot be motivated by fear anymore than his addiction can,
If you encourage him to leave, than you risk encouraging him in this lifestyle, my advice would be to attempt to treat him as an adult with a serious problem with living, and to try and encourage that living again, educate him, love him, and if you can keep it up for a year or so, hopefully he will see what wonderful parents you are, and his love and respect for that may swing him round,
I was all the things and worse that your son is, I also left home, in hindsight, at the time, I did it because I was fed up being treated like a child, (even though I acted as one most of the time), I ended up going quite far down the road, but my parents were fantastic throughout, even though I know I hurt and upset them sometimes, as they get older now, I feel a huge desire to ensure their older years are as peaceful and happy as possible, for they gave up a lot, and suffered ridicule, for always sticking by me and my brother, even when we were vile people,
I would also say, please recognise the difference between a normal teenager doing (what is today) normal teenage things that just need reigning in a bit, and possible long term addictive behaviour, please do not try and crack a small nut with a sledgehammer, make deals, set rules, allow setbacks, concentrate and push forward the concept of your family and what it means to all of you, be forgiving, be firm, try and stay clear of theatricals, set your objectives as a family, enlist his help,
Hope that helps