The Science of Caffeine Addiction
Just like alcohol, prescription medications, and many other drugs, caffeine is physically addictive. Physical addiction means that after extended use, the user's body becomes so accustomed to receiving the drug that discontinuing it produces physical symptoms- in caffeine's case, these include headaches, lethargy, muscle pain, lack of concentration and more.
Much like other drugs, your body becomes addicted to caffeine because of the way caffeine functions in the brain.
Caffeine works by blocking off the brain's adenosine receptors. Adenosine is a molecule that is naturally produced by the brain through processes such as cellular respiration; as adenosine builds up in the brain, it produces a feeling of tiredness.
When caffeine molecules plug your brain's adenosine receptors, your brain is no longer able to absorb adenosine, which negates its natural tiring effects. This- coupled with the fact that blocking adenosine receptors increases the effectiveness of other natural stimulants- is what gives caffeine its stimulant properties.
In people who use caffeine on a daily basis, the brain's structure and chemistry change to adjust to the lack of adenosine. This includes the growth of more adenosine receptors. And as the brain grows additional places to absorb adenosine, you'll need to drink more and more coffee to achieve the same result.
When you cut caffeine out of your diet completely, your brain chemistry is suddenly altered. The increased number of adenosine receptors (that now have nothing to block them) coupled with a decreased volume of natural stimulant receptors (another reaction to caffeine) causes a variety of symptoms, including the all-too-common (and very painful) caffeine withdrawal headache.