Tuesday, August 19, 2008

Intoxication, Addiction and the birth of Addiction

Foreward (written after the post): This article is very vague in what it tries to explain - the evolutionary insight into addiction. It actually relies on evolutionary theory.

This post is a little about what happens in the brain when we get intoxicated or addicted to a substance. I suppose this post will highlight a little about the neurobiology of the brain. I don’t consider everyone to be an addict in any way; but I believe people are more susceptible to be a victim of addiction in general. The only way to understand ‘why this is so’ is to understand the biochemistry of the brain, and a little evolutionary history about it. Before I move on, I just want to clarify the two terms – intoxication and addiction:

Intoxication is the state of being affected by psychoactive drugs. It may also refer to the effects of consuming poison or excess amounts of harmless substances. Since I am not talking about intoxicating substances which are lethal or cause instant death I am ruling out the second definition. Intoxication may result in relative euphoria, feeling of pleasantness, etc. These are common symptoms. However not everyone experiences the same symptoms the same way. For some the relative euphoria is a sign of panic, and hence they develop a hate toward these substances. However the general trend is that people rather enjoy the feeling. Addiction is the next level of intoxication. It is much more serious. It is the physical dependence on a psychoactive substance which, when suddenly stopped, causes what is known as withdrawal symptoms. Some common withdrawal symptoms are anger, lethargy, depression, anxiety, etc.

Brain Evolution
Sometimes our brain can be considered to be a huge response system. It responds to various stimuli. And to get these signals or messages across to various regions for processing, the brain relies on its intricate mesh of neurons and neural network. There are some signals that can trigger panic, or readiness to attack, etc. These particular signals are ‘wired’ for the primary reason of survival. We perceive panic or the readiness to attack through a phenomenon called emotion. Neurologically, this is how we would behave when there are certain levels of chemicals (neuro-transmitters) present, taking a particular emotional phenomenon in context; for e.g. when feeling sad or suffering from anxiety, we can observe high amounts of a neurotransmitter called serotonin. (Serotonin has other function like regulating sleep, the cardio-vascular system, etc).

There are two kinds of emotion – positive emotion and negative emotion. Positive emotion works in a scenario where the brain (or the organ called the brain) has realized that there is something positive. For e.g. edible fruits on a tree. If we come to know that we are able to eat fruits from a tree, and that they are abundant, we would naturally be happy. This is a positive emotion which would make us want to consume more fruits from that tree. You can derive a corresponding case for a negative emotion too. Hence as a conclusion you can say that the brain seeks positive or rewarding scenarios most of the time for the simple reason called survival.

The reward system
Now that you know that the brain seeks for positive signals, you should also know that there exists neural pathways or channels and/or reactions which would generally come under the an umbrella the reward circuitry system. In the days of prehistory, the reward system in humans was relatively undeveloped. Perhaps early humans who primarily relied on hunting/gathering for survival did not require one. They were not exposed to intoxicating substances like modern humans. Reward for them was being a successful hunter and acquiring lots of food. Or being reproductively successful, etc. But as food became scarce they became physically unfit for hunting; they discovered that these intoxicating substances could boost their hunting stamina, or even sometimes their reproductive success. However, these substances were not administered in amounts that would cause chronic addiction.

As we became more civilized and started to settle our urge to hunt and feel superior etc, still remained. These programs were still running inside their brains. And consuming intoxicating substances was the only way out. Thus we see the evolutionary birth of addiction.