Hey Leigh, thats a really interesting question. Addiction is a very complicated process – as much physical as emotional really. Drugs can alter the brains chemistry and neural pathways over time, creating effects. If our mind/body enjoys these effects, then the brain encourages more exposure to these, but at the same time becomes less and less sensitive to the effect.
A colleague of mine is working on the science behind addiction and entered a dance competition illustrating the process of addiction – have a look!
People can become addicted to horrible things like drugs, but also to more common things like coffee and sugar. Drugs cause a physical and psychological dependance. They chemically alter a part of the brain called the reward system. The drug and even sugar (but to a lesser extent), for example, trap the chemical dopamine in the spaces between nerve cells. Dopamine creates the feeling of pleasure that we get from enjoyable activities like exercise and from eating. But with addictive substances, dopamine keeps stimulating those cells, creating a “high” or euphoric feeling that lasts for a long time (5 to 15 min). When it wears off the person is left feeling down and depressed, resulting in the desire to have more to feel better again. You have a very inquisitive mind Leigha! you ll make a great scientist some day 🙂 Hope that helped!