Was Holmes written as a drug user in A Study In Scarlet?

Question

In The Sign of the Four, Holmes is a drug user:

Sherlock Holmes took his bottle from the corner of the mantelpiece, and his hypodermic syringe from its neat morroco case. With his long, white, nervous fingers he adjusted the delicate needle and rolled back his left shirt-cuff. For some little time his eyes rested thoughtfully upon the sinewy forearm and wrist, all dotted and scarred with innumerable puncture-marks. Finally, he thrust the sharp point home, pressed down the tiny piston, and sank back into the velvet-lined armchair with a long sigh of satisfaction.

We don't see any evidence of this addiction in A Study in Scarlet, but we do see this line:

On these occasions I have noticed such a dreamy, vacant expression in his eyes, that I might have suspected him of being addicted to the use of some narcotic, had not the temperance and cleanliness of his whole life forbidden such a notion.

This exactly describes what is happening, in-universe - he is taking drugs on those occasions. But Watson is saying that he does not see him taking the drugs, although they had been together 'many weeks'.

So - was Doyle actually writing him as taking drugs then, and Watson somehow failed to notice, or was he not (out of universe) taking them and that was a later decision?

Answer 1

Let's clarify: Holmes was taking a 7% solution of cocaine, which is a stimulant. Watson is saying that Holmes would never take a narcotic, which is a depressant. At the time, cocaine was not considered any harder of a drug than alcohol; it wasn't the deadly drug we see it as now. Coca-Cola actually had the coca leaf in it originally.

If you recast the first quote as "Holmes getting steadily drunk at a pub on shots of fine whisky" and the second as "Holmes shooting meth," you have more of a modern equivalent. So yes, Holmes was abusing a mind-altering chemical, but Conan Doyle wasn't intending to present him as a gutter-crawling junkie.

Answer 2

For the last comment of @Mithrandir, A Study in Scarlet does not include such a line.

As for that, the beginning of ASiS shows that Holmes regularly received visitors, and that Lestrade came by frequently.

Presently, however, I found that he had many acquaintances, and those in the most different classes of society. There was one little sallow rat-faced, dark-eyed fellow who was introduced to me as Mr. Lestrade, and who came three or four times in a single week.

This shows us that Holmes was solving cases at that time.

In A Sign of the Four, we see that he was going through... a lull, it could be said.

"My mind," he said, "rebels at stagnation. Give me problems, give me work, give me the most abstruse cryptogram or the most intricate analysis, and I am in my own proper atmosphere. I can dispense then with artificial stimulants. But I abhor the dull routine of existence. I crave for mental exaltation. That is why I have chosen my own particular profession,—or rather created it, for I am the only one in the world."

The only reason he took Cocaine was because he was bored. The time during ASiS, I believe, which was spent during the 'expression of extreme vacancy', was actually him thinking on some cases he had acquired, instead of Cocaine or Morphine.