It is a commonly known fact- supported by years of scientific research- that the use and abuse of any illicit drug or alcohol cause drastic deterioration in the way one thinks, feels, and behaves. 

Before we talk about this deterioration, let us look at the role our brain plays in our thinking, feeling, and behaving. 

Every thought, emotion, or action we experience involves our nervous system- our brain, spinal cord, and the nerves that extend throughout our body. The neurons are the millions of cells that are responsible for the functioning of our nervous system. They use positive and negative charges and chemicals (called neurotransmitters) to send messages to and from all the glands and organs to the brain, which in turn evokes responses. 

Dopamine, serotonin, endorphins, and gamma-aminobutyric acid (GABA) are the four main neurotransmitters involved in substance dependence. We all know that drugs and alcohol change our mood- they either make us feel extremely happy or depressingly sad or any other emotion that can be encompassed in the spectrum between these two. 

The question is how do they do it? The simple answer is that the change in the actions of the neurotransmitters. Drugs and alcohol could either change the way neurotransmitters are produced, released or sent. OR they could imitate, block or enhance the effect of a neurotransmitter. The result is a change in one’s mood. Thus, thoughts like “I feel good” or “I feel bad” change into “I need a drink” or “I’ve got to have a hit.” An individual gets addicted to a mood-altering substance because it changes the way neurotransmitters work, which leads to intense feelings of pleasure. 

Scientists believe that people with low levels of dopamine, serotonin, endorphins, and GABA in the “pleasure center” (medial forebrain bundle) of the brain experience a lower level of pleasure. Hence, they seek drugs and alcohol- that work on neurotransmitters- to experience feelings of pleasure. Besides altering the way neurotransmitters work, repeated substance use can change the pathway of dopamine (the “feel good” chemical) through the “pleasure center” of the brain. 

In simpler terms, it could cause one to either like a drug because it makes them feel happy, want a drug to fulfil their craving, or to absolutely need a drug at a primal level. Once a need pathway is formed, the individual continues to use the substance, despite it not really making them happy or crave it. This makes them believe that they need the drug or alcohol to survive, taking all sense of control away from them. 

Thus, addicts usually talk about how once they start drinking or using, they cannot stop any more than they can stop breathing. In sum, addiction is not only a disorder or the brain but also a disease of the body and a sickness of the soul.