Confusing a possible cause with the only or most important cause

What fallacy is this?

I see a lot of arguments that basically go:

A can cause B
B is present
A is present
Therefore A caused B

Basically this seems to be a confusion of probabilistic or quantitative causality with absolute causality or qualitative.

For example,

Lead poisoning can contribute to violent behavior
Many inner city chldren have dangerous levels of lead in their blood
Therefore violent crime in the inner city can be solved by curing the lead problem

or

A sedentary lifestyle contributes to obesity.
People have become more dsedntary in teh last few decades.
Therefore the risie in Obesity can be fixed by people getting more exercise.

or

Stress can weaken you immune system
People with weak immune systems are more likely to get colds.
I was recently under streess that must be why I got a cold.

In all cases , the relative contributions of the named cause to teh problem is not considered compared to possible other known causes, nor is considerations made for the magnitude of the effect possibly due to unknown causes.

This is a VERY common fallacy and should have its own name, but doesn't (that I know of). This falls under the cognitive bias known as black and white thinking . It is a form of simplistic thinking that implies something is either a cause, or it is not. It overlooks the important fact that, especially when referring to human behavior, causes are very complex and multi-dimensional—referred to in science as casual or contributing factors . The form looks like this:

X is a contributing factor to Y
X and Y are present
Therefore, to remove Y, remove X

The line between a fallacy and a reasonable argument has to do with the absolute term used in argument. Let's take one of your examples:

Lead poisoning can contribute to violent behavior
Many inner city children have dangerous levels of lead in their blood
Therefore violent crime in the inner city can be solved by curing the lead problem

The fallacy is due to the word "solved". If we change this word to something such as "mitigated" or better yet, rephrase the statement to something more probabilistic such as

Therefore, curing the lead problem might reduce violent crime in the inner city.

We could avoid the fallacy.

I will put this one my list when naming new fallacies #newfallacy.

In all the above examples, the fallacy, as some critical thinking call it is oversimplified cause fallacy .

I just want to add the fact that in the examples, the presence of A and B or X and Y does not imply by default causation. Does lead really cause violent behavior? Or just can cause, as in the example.The first premises in all the examples, look to me, like hypotheses (if they are derived from some scientific theory). It is a matter of empirical inquiry to establish if they correspond to reality. If it is the case that research supports the first premises, the person making these claims is still guilty of committing this fallacy because of the reasons Mr. Bennett presented.