Drugs and vices in general seem to create a wider range of possible happinesses for you. Meaning, consuming alcohol for example, allows you to reach higher levels of happiness and lower levels of sadness.
You can imagine the above chart as a sort of stochastic oscillator, where the stock price is your happiness, and adding vices increases the volatility of the stock price (happiness).
Note: If you are very enlightened, then you can reach the higher levels of happiness without a vice. This post is for the person of “average enlightenment”.
I believe that on mean average, at any given point in time, use of vices and non-use of vices result in the same amount of happiness. I believe, slightly higher happiness with the use of vices. 
Of course, we know vices are bad, and create unhappiness. When I was young, I naively believed it was simple as: use of vices causes you to be addicted and take over your life. However, there are two more subtle damaging effects.
1. It hurts your ability to enjoy non-vices.
Drugs can in fact, feel better than anything else. That is why they’re so damaging.
If you become a chronic drug user, even if your body returns to pre-drug-use levels of seratonin production etc., you still have experienced higher highs than what is naturally possible.  In comparison, the world can feel “gray”.
2. Your lower lows will pass a breaking point.
So, if on average, vices make my life better, why would I not do them?
As you increase your upper and lower bound happiness, your lower bound happiness will eventually pass a breaking point. The breaking point event is so specific to each person that it’s hard to describe.
The most pertinent analogy is a gambler (unsurprisingly, also a vice). We have a fictional gambler, who starts with $1000. She’s betting on a coin flip, and she’s using the Martingale betting system. That means if she bets $1000 and loses, she’ll bet $2000 the next time. If she loses on the next flip, she doubles her bet again, etc.
She has an equal chance to hit +$100,000 and to hit -$100,000. The problem is, she may go bankrupt at -$80,000. Once she is bankrupt, the game is over. There is no equivalent game-ending event for her hitting +$80,000 besides her own discipline. Of course, laws enforcing bankruptcy are stronger than self-discipline, especially under the influence of the excitement of gambling.
Making heavy-use of vices is gambling with your happiness in the same way. You will hit your bankruptcy-like event.
 I understand that this is a contentious opinion. That is just the experience of my life. I absolutely understand if you disagree.
 I’m talking about measuring simple seratonin levels of happiness. There are deeper levels of happiness, like love for family, self-actualization and contentment. They do not apply for the purposes of this essay, although they are the more noble types of happiness.
 This post may be alarming to people who know me. I’m not in any danger of over-use of vices. This is a post I’ve thought about for a long time, but I’ve refrained from posting for fear of that reaction.