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When I talked about marijuana yesterday I failed to properly address one of the key arguments people have against it: it’s a gateway drug.

Honestly, I think that this is another case of us mixing up correlation and causation.

A little definition:

Correlation: X and Y happen at the same time, but they are not connected. They could also happen at different times.

Causation: X and Y happen at the same time, and they are connected. X causes Y to happen. In most cases, Y could not happen without X.

It is easy to get these two confused because what one observes–X and Y happening at the same time–occurs in both cases. I feel like this is what is happening with marijuana. When you talk to heavy drug users, and drug addicts you will find that the majority of them have used marijuana at some point in their lives. Without any further evidence, this could lead to the erroneous conclusion that smoking marijuana caused these people to decide to try harder drugs, which they then became addicted to. This isn’t evidence. Scientifically, we could not use this small set to argue marijuana is a “gateway” drug.

What we would need to do is take a large sample of people and find out who has tried marijuana. A recent poll suggest 38%. We could then use this same sample and see how many of these people became drug addicts. I’m having trouble finding a statistic for this, but one I found says that currently 9% (that number includes those who are currently using marijuana) of the US population uses (not even addicted to illegal drugs, even just using them occasionally)   If we believed that marijuana was a gateway drug then almost all of the people who have tried marijuana should have become drug addicts, and the a large proportion of them would probably be using drugs now. This is certainly not the case. All you have to do to confirm this is to think of the people you know: how many have used marijuana? Are they all addicted to harder drugs now?

What is the case is that marijuana is a common ‘first’ drug (after alcohol). 62% of drug users used marijuana first. This makes a lot of sense for someone who wants to try drugs. After alcohol, marijuana is the most readily available drug.

Basically, the evidence does not suggest that marijuana use leads to harder drugs and drug addiction. IF you are still reading this and disagree with me then think about this. More than half of American adults are current drinkers (my marijuana statistic just talked about trying marijuana at some point). I can’t find a statistic for it, but I will bet a lot of money on the fact that the majority of drug addicts have “used” alcohol at some point in there lives. Probably more than have used marijuana. Given this, couldn’t we say that alcohol is the gateway drug?