First let's use the example of addiction. It’s not a physical, organic thing. The addiction is a consequence of learned experience and repetitions of patterns. So is alcoholism in the genes?
The answer is no. In the science of epigenetics it’s been found that it’s the perception of your environment that controls your genes. You’re not a victim of your genes because you’re the one who can change your environment—or, more importantly, change your perception of your environment—and thus change your response to it.
Let me tell you some fundamentals of how the mind works so this will be more clear to you. The cells of your body are merely following instructions given by the nervous system, by the brain. The nervous system does the interpretation. You can easily see this when you see two people reacting to the same stimulus with very different reactions, one positive and one negative. As your perception changes, you change the message that your nervous system communicates to the cells of your body. Your mind controls your biology. That’s what the placebo effect is about; the mind believes the pill will work and so it does.