Just as the placebo effect causes spontaneous healing, the nocebo effect shows how the power of your beliefs can interfere with healing, induce illness, cause you to injure yourself, and fulfill your doctor's prognosis that you only have so many days to live.
Nocebo means "I will harm". It is the flip side of how your mind heals you via the placebo effect. Just as you get positive results from your deeply held affirming subconscious beliefs, you get negative outcomes from your deeply held negative beliefs.
Keep in mind that your subconscious mind is not purposely trying to hurt you. Placebo and nocebo are just terms people use to describe what we perceive as positive and negative outcomes. The job of the unconscious is to carry out your programming. Since it does not actually think and reason like your conscious mind does, it does not realize that one of your beliefs is any better than any other. Think of it like your computer. It will carry out all instructions your software gives it, including the newly downloaded software that tells itself to destroy itself with a virus.
Your unconsious mind is still doing its job of pleasing you by creating reality from your beliefs. It is doing its job of making you right. Unfortunately, when considering the power of the nocebo effect, those ways are not usually what you consciously desire.
For example, if you believe a medication will have side effects, you will probably experience them, just like participants in research studies do when they are receiving a placebo, or sugar pill. Why would you believe so strongly what you were told, that you would generate side effects from nothing ? Because an authority figure told you so, or your belief system is that pharmaceutical drugs are bad. You may have read about side effects on the label, heard it from your doctor, or you witnessed someone else suffering from them. Of course, the potential for side effects in actual pharmaceuticals is very real. They do alter how your body functions. Your belief system or programming is just one factor in determining whether or not you suffer from them, and how badly. (wiki image license)
This negative power of your beliefs may also explain why people faithfully develop the generational family illness even when they are adopted with no blood ties. When there are blood ties, your doctor may have reinforced this belief for you by putting you in a high risk category and scheduling you for regular testing so that when the inevitable happens you can treat it quickly. Again, genetic vulnerabilities are very real, but according to the study of epigenetics, so is the fact that how you take care of your mind and body is a far better indicator of when and if you contract those scary diseases. Could it be possible that the real reason you all get that disease also be that you were all exposed to the same toxins, or all have similar lifestyles and beliefs?
The nocebo effect is not limited to your beliefs about wellness and healing. Deeply held beliefs about deserving, self-worth, abilities, money, and all areas of your life play a part. For example, why would your subconscious mind help you open doors to wealth if you really believe that rich people are bad or money is evil?
Unfortunately, because the subconscious mind is primarily concerned with safety and survival, it is constantly on the look out for danger, or negatives. So when it comes to the power of suggestion, negatives may carry even more weight than positives. Combine those beliefs with a healthy dose of fear and you create a powerful synergy that throws you into a state of stress that causes your subconscious to take action. A perfect example of this is people who believe in voodoo being scared to literal physical death when they know they have been put under a voodoo spell.
A few random negative thoughts are not going to convince your subconscious to act and make you ill, but deeply held beliefs and repetitive negative thinking patterns accompanied by emotion just might. Listening to your self talk and identifying your core beliefs is the first step to shift from nocebo to putting the power of your healing mind to work for you.