Trading is a stressful job. When in a trade, you can have difficulty sleeping soundly and enjoying your free time. And I believe a lot of inexperienced traders maybe tempted to turn to drugs in order to cope with the stress and anxiety----as a kind of temporary escapism from the anxiety.
Drug taking for this reason is a bad idea, and if you start dabbling with drugs then you should correct your lifestyle, or change jobs. I believe you can't be a good trader and take drugs because drugs alter your state of mind and thus your perception of the markets. Drugs cause euphoria and other chemical highs that may encourage stupid risk taking, which is deadly in the markets.
If you feel anxiety?
You should chart out a trading plan and ideology, and use stop losses. I often don't use stop losses, but if I'm anxious about a trade, I use them. They certainly help to reduce anxiety. If your timeframe is long, you might implement a stop loss after a profit is secured, so you can step back and let the instrument run, and then periodically move the stop loss.
The only intoxicant I find improving of my trading is red wine and brandy. Red wine makes you drowsy and you sleep better, and a finger of brandy before bed often encourages nice dreams. Red wine is also a depressive, and a depressed alcoholic should easily out-trade some drugged-up hoper.