Addiction affects millions of Americans. It's not simply a failure of will or character; it is a disease of the brain.
 
According to various estimates, about 3.6 million people in the U.S. are addicted to or dependent on a wide range of drugs.  Many are addicted to more than one.  In addition, there are about 18.7 million alcoholics. Millions more are functionally addicted to things we don't consider drugs, such as tobacco, caffeine and food, as well as to activities such as gambling, shopping, sex and spending time on the internet. 

Of course, the term addiction can be used too loosely, so let's look at some definitions.  Addiction is diagnosed by considering people's behavior. How much do they seem to need the substance (or addicting agent) to function?  What are they willing to do to get it?  How reckless and risky do they act while feeling its effects? How much do they ignore other things in their lives as they pursue what they're addicted to?

The line between addiction and substance abuse can seem vague, but medical professionals have specific criteria to distinguish them.  Substance abuse causes harm to the user; people are considered to be abusing a substance if, during a twelve month period, they do any one of the following:

• Fail to meet responsibilities (educational, professional, or social) because of it
• Act in a reckless manner while under its influence
• Have legal problems because of it
• Continue to use it despite knowing the problems it causes

Addiction is a more severe condition, and involves doing more than one behavior.  The American Psychiatric Association lists a number of behaviors it considers symptomatic of addiction, and says a person must do three or more of them within a twelve-month period to be considered "substance dependent."  Among the symptoms are:

• Developing a "tolerance" for the substance. Tolerance means needing increased amounts of it to feel its effects or feeling a decreased effect when using the same amount
  
• Suffering withdrawal symptoms if one stops taking it or decreases the amount one takes. Withdrawal symptoms include an array of unpleasant effects, ranging from minor (such as sweating, anxiety) to the severe symptoms associated with withdrawal from narcotics (such as pain, cramps, tremors, and nausea)
  
• Losing control, as shown by:
• Taking more of the substance than planned
• Trying but failing (several times) to stop using it
  
• Spending a lot of time trying to get it, use it, or recover from its effects
  
• Ignoring other activities (educational, professional, social, or personal) because of its effects
  
• Continuing to use it despite knowing the physical and/or psychological problems it creates

In the past, this kind of behavior was seen as a moral weakness or spiritual failing. Today we know that addiction is a disease of the brain.  What does this mean?

In recent years, clinical research into addiction has been greatly aided by sophisticated imaging technologies that let us look at the brain and see how it changes because of addiction.  It appears that addictive substances alter the nerve cells (neurons) in the brain, which affects how they transmit and receive information.  Addictive substances, therefore, are things that can create these changes in the brain.  Obviously, not all drugs have this effect; therefore, not all drugs are addictive.

Each substance can cause different changes, but in general they seem to affect the "reward circuits" or "pleasure pathways," the information pathways that tell the brain when something (a substance or an event) is pleasurable. The changes can make normal, pleasure-producing things seem less pleasurable, while reinforcing the need to use the addicting agent. 

Other parts of the brain can also be affected, including those that control the memory-making process, decision-making skills, judgment, desires, emotional responses, and motivation. The result of all these changes is that the brain is "re-wired" so that it produces an all-consuming, uncontrollable craving for the addictive substance, a craving that overwhelms the addict's normal needs, desires, and sense of values.

These changes in brain structure and function can last a long time, even after a person stops using the substance(s) that created them.  But some changes may be reversible.  That's why treating addiction is as important as treating any other disease.  

Learn more about Addiction: