Sometimes, when one has an addiction, finding something else to be a "positive addiction" is the thing that will keep you on the straight and narrow. And it has to be something you're passionate enough about tha it makes being an addict much, much less desirable.  It's an addictive personality thing. That's what I think Sherlock is talking about. 

I agree.
Well, Janine and he may have shared a bed, but there was no sex.

I don't know about heroin but if you don't tell people that you're high a lot of them won't notice (I had a very wild youth...) It is not like alcohol which one would smell. If you are already labelled as "strange" people just think it is your "strangeness".
Maybe Sherlock took just as much that he still would "work".

I've heard him say that he does, trying to look sort of otherworldly.
 

Well he's certainly succeeded with the other worldly thing.  I actually found myself thinking the other day that he looks rather like an elf.  (A Tolkien elf of course)

Lily wrote:

Sherlock's remark in HLV really confused me: 'Your best friend is a sociopath who solves crimes as an alternative to getting high.'

I found the whole interaction which that was a part of confusing - Sherlock was trying hard to get John to believe that he is attracted to sociopaths in general and subconsciously knew Mary was a sociopath, which is more than I can believe the subconscious capable of (more in the Sherlock / John / Mary dynamic thread on that point).

I believe Sherlock was in the drug den to try and fool Magnussen - he was too focused to be doing heroin seriously, and the house John found him in seemed to be a 'shooting gallery' for smack heads, not people doing cocaine.

BBC Sherlock seems to me to like excitement, I doubt he'd want to quiet his mind down.  If he was doing drugs I think he too would go for cocaine.

I think the heroin has been brought in as an updated reference to canon (Moftiss do love updating canon) rather than to tell us anything particular about Sherlock.  I'll be surprised if we see much more on this point in show - Moffat has said a couple of times he regards people doing drugs as 'twats'.

True, but in canon he hadn't partaken of the drugs, hence the opportunity for varying Interpretations of the significance of Sherlock doing (probably) heroin in HLV.

BTW, how did the drug become heroin? It was opium in the canon and opium was also on CAM's list. 

I know, or at least I think I know, that opium isn't very popular these days so heroin would be a more obvious choice in an updated version but it's never suggested anywhere that it's heroin and not opium. 

Isn't taking heroin also considerably more dangerous? Quite a risk for a case. 

Criosdan wrote:

Opium and heroin are related. It is an opioid.

Raven: Thanks for the information. Although, I have several experiences with drugs, heroin is none of them. (By the way, I'm a bit curious who would be really surprised if they knew. When your're different, all kinds of gossip appears...)

Swan: One can smoke it, inhalate it like cocaine.

Actually, that's true-- and I've seen people do it--(never did it myself, wasn't completely without sense) people would put coke and heroin in ciggarettes and smoke it. When opium is smoked, it smells lovely-- like perfume. I've actually done that ( in the 80's) it was lovley, and I never did it again. People have also been known to mix it with Hashish. 

Real junkies will shoot places , like between their toes, usually when they've ruined their veins, or want to avoid being obvious. 

Yech. Nasty, but effective.

Criosdan wrote:

Opium and heroin are related. It is an opioid.

Thanks, I did know that. But even drugs from the same chemical class can have quite different effects on the body, also much dependent on the dosage and the efficacy. I'm not an expert but as far as I remember, both of them are GABA agonists, much like benzodiazepines, but what makes them so dangerous is of course the effect on the dopamine system. I suspected that heroin might be a stronger dopamine agonist than opium, but on reflection it might just be the way it's taken and the dosage. Opium is mostly smoked and heroin mostly injected, so the effect of heroin would be stronger. 
 

I don't know much about drugs. I didn't know you can smoke heroin, for example. It makes more sense that he might do that than shooting. I missed the spoon thing and CAM thought it was opium, that's why I was confused. But heroin seems to be a more up to date version, true.