Mechanism of Addiction

Mechanism of Addiction

October 16, 2015

In previous article, I described the cause of addiction and how the stress and emotional issues can increase the vulnerability to addiction. In this article, I will describe how biology and evolution are involved in addiction.
It’s no doubt we human are the amazing creation of Mother Nature adapted and evolved through millions of years of evolution. But, have you ever wonder, we human despite being the result of millions of years of evolution and having made everything for our benefits, why we are still vulnerable to addiction which only affects us, prevent our growth and development and why the mechanisms that leads us to addiction still within us. I hope the following articles will help you better understand these things.
Programmed to Survive:
Well to understand this we have to start from root level and go back to our past, as a living creature main purpose of our body (and all living beings) is to survive and prevent our species from getting extinct with the help of reproduction. The act of searching water for drinking, the act of searching and feeding oneself food, the struggling and fighting for mating and other activities related to our survival are the things, that assures the survival of ourselves and of our species as a whole. So, in order to make these activities motivating and appealing our body has developed a pleasure center in our brain, whose job is to promote and reward those activities that supports or increases the chances of our survival.
Neuron
In the figure, right one is a nerve cell and left one represents a junction between two nerve cells which is called synapses. Our brain communicates through neuro-chemical signals. There are numbers of neurotransmitter which helps in communication, but dopamine is the neurotransmitter which is commonly associated with pleasure and reward. The pre-synaptic neuron contains vesicles containing dopamine whereas dopamine receptors are present in post-synaptic neuron. When we do something pleasurable, dopamine is released from vesicles, they move through dopamine transporter and bind with dopamine receptors, and stimulate the receptors, hence we feel satisfied or pleased. After stimulating the receptors, the dopamine again returns back to the vesicles for future use. This is how pleasure circuit works.
Enjoying the High With Dopamine:
Affect of cocaine in neuron
Now, what the drugs and alcohol do is, they hijack the pleasure center. The chemicals from drugs or alcohol enters the brain, stimulate the pleasure center causing release of dopamine and it even blocks the dopamine transporter, which prevents the dopamine from returning back to vesicles as shown in figure in the right side. Since our brain don’t have the mechanisms to remove these chemicals from blocking dopamine transporter on its own, so it rely on liver to break them up through metabolic process but metabolic process is much slower compared to the normal neurotransmission process, which takes place within a fractions of second. This causes dopamine level to rise in the synapses region and dopamine binds with receptors for longer time than usual. This causes prolonged sensation of pleasure which rarely occurs during normal activities related to survival. This makes sense when addict of strong drugs like cocaine explains experiencing multiple orgasms throughout a whole body when using drug.
But gambling, overeating, unhealthy sexual activity, exercise etc doesn’t include intake of any external substance so you may ask, why they are still addictive. Well, there is another explanation for this; Food and sex are the important things needed for survival, so it is obvious inorder to make them more appealing, dopamine should be released. Gambling involves skills of taking risk for higher benefit or reducing or eliminating risk, such skills used to be helpful for our great great grand parents in the jungle in order to avoid risk while hunting prey, encountering predator or facing threat to survival. Exercise and hot spicy food on the other hand don’t produce any comfort but they release endorphin in our body to deal with pain and stress caused by them and which eventually releases dopamine.
But difference between now and past is; in past while our ancestors used to live in forest, food was scarce, it wasn’t easy to find novel sexual partner, you wouldn’t have to get involved in risky activity frequently but now things have changed there is a huge supply of food, you can have sex with new person everyday or at least can fool your mind through nude videos, gambling is not a problem you can gamble at local casinos or in online gambling sites 24/7. Not only this, today in just a moment of time, one can find foods, nude videos or sexual opportunities, gambling activities in such a massive amount which our great ancestors would not even used to find in their entire lifetime. So, since our biological pleasure system is not made for this type of overload situation, which then gets hyper as a result. Hence, our mind gets fooled, and releases large amount of dopamine continuously as long as we get involved.
This is how the mechanism developed in our system through millions years of evolution in order to help us survive, can pose a great threat in the today’s society if we just keep on following our natural instincts.
(Picture Credit: The Addicted Brain by Michael Kuhar)
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