I know that in the canon of the books, Sherlock Holmes used drugs. I also know that in ASiP Sherlock had a suspicious reaction to the ‘fake’ drugs bust eluding to the fact that he has at some point used elicit drugs. In the pilot he even comes right out and says it. The cabbie asks if he likes drugs and Sherlock replies, “Not in awhile.”
All of this seems very contradictory to some of the other BBC Sherlock canon statements. Sherlock is all about his mind and using it to parse out the truth of a situation. In TGG he describes his mind as his “hard drive and that ordinary people fill their heads with all kinds of rubbish and that makes it hard to get at the stuff that’s really important.” He becomes extremely agitated with John insisting that he can’t believe Sherlock doesn’t know simple primary school knowledge and starts yelling that “All that matters to me is the work. Without that my brain rots.”
In THoB he is quite literally freaked out by seeing the hound. It makes him doubt himself and that is a very uncomfortable situation for Sherlock not to mention something he has never experienced before. He knows that he saw the beast, but logically he couldn’t have. He says, “I’ve always been able to trust my senses, the evidence of my own eyes, until last night.” He came right out and said that he has never experienced doubt of his senses before. That tells me that he has never used drugs due to how they effect the function of those very same senses.
Given this about BBC Sherlock, it seems to me that taking drugs that alter one’s perception would be almost offensive to a man like him. He relies on his abilities to observe everything around him. His brain automatically takes it all in and begins to categorize all that input. Anyone could understand that the use of drugs would be a way to shut that off for a little while, but going by how BBC Sherlock describes himself and the workings of his mind, I don't really see him choosing to willingly hamper his ability to perceive the world around him.
The only reference we see of his possible drug use in the series is the ‘fake’ drugs bust. From that point forward the only substance he seems to have difficulty with is tobacco. Given these contradictions within the series I am unsure whether or not to think that the BBC Sherlock actually uses, or has in the past, used drugs. Opinions?