There is no specific addiction gene but there are genetic variations that can confidently predict a tendency for addiction. Is a tendency for addiction an emotional behavior?

If you remain here for much time, you'll notice that I often mention ratios. Often with an accompanying, "And I don't know what that ratio is in individual instances or as a generality." The influence ratios of genetics, environment and nurture are a frequent topic of debate. I am not one to completely dismiss any of them. People generally have no issue with genetic influence until it touches a 3rd rail issue like intelligence. Another ratio appears; how many are looking at the technical merits of the issue and how many don't like a possible resultant conclusion. History shows that the idea has led to some awful things and "where does this lead/what is the objective" is an influencer with me. There is too much that is unknown for me to argue the amount of influence under various situations.

Recently an eye surgeon discussing a spot on my wife's eye said that if she was white, she would be more concerned about it being cancer but because she is highly melanated it is more likely to be melanosis than malignant. More likely was not the only decision point and she had a biopsy. Melanosis.

As a retired test engineer my bias is toward the idea that testing does tell you something although I can tell you about things with more precision than people.