> That is, if it isn't 1:1 in correlation, then it is reasonable that you can prevent suicides by limiting access to guns.

The problem here is you're assuming that there's a singular dominant causal factor. You don't need a one-to-one relationship for either a weak or strong causal relationship.

On the other hand, what I'm claiming is that there are causal relationships between gun suicides and drug overdoses. That solving one will help solve another if we look at the causes from a standpoint beyond the first order viewpoint. We need to ask why people are depressed and what in society is causing that. I'm sure you'll recognize that this issue is likely rather complex. I think you'll agree that getting to the root of this issue will save more lives overall (some people will for sure just choose an alternative method of suicide -- such as drugs -- though you are also likely to save a few that are acting in the moment and getting a gun -- which is why waiting periods can be helpful. But either way, they are still depressed, which is a problem we need to solve).

From the studies I'm seeing, limit access to the means of suicide, and you reduce suicides. Do you eliminate them? No, but a reduction is still a reduction.

Note most of the studies I saw were not about guns, but pesticides. I see no reason to think they would not apply similarly. Would be nice to see studies in them.

Now, should we /also/ try and tackle more issues down the chain? Yes. Not sure why this has to be a "pick one" scenario.