Addiction to drugs, sex, or even food can occur due to these things causing an elevation in the naturally occurring neurotransmitter dopamine.  Dopamine increases the brain’s ability to perceive pleasure, and activates reward reinforcement.  Addictive drugs such as heroin, cocaine, prescription painkillers, and methamphetamine may increase the brain levels of dopamine by five to ten times.  The limbic areas of the brain (emotion, pleasure) are reinforced by repeated exposure to the things that cause for that person a massive increase in dopamine, and the brain learns this pleasure activator very rapidly.  The next exposure to the same drug reinforces the pleasure, causing an intense desire for the drug (or food or sex) again.  With continued repeated exposures over time, the nerves responding to dopamine become less sensitive (desensitization) leading to behavioral changes in order to replicate the pleasure received- the person begins using the drugs more often in order to achieve the same degree of pleasure, and frequently higher and higher doses of the drug is needed to achieve the same effect, especially with prescription painkillers and heroin.

 

The expectations of the brain may be involved with addiction.  For instance, an ice cream shake is known by a person to taste great, but there is little dopamine released in anticipation of receiving it.  But with drugs, especially prescription pain killers, you can never learn to expect it because dopamine on usage produces far more dopamine than with ice cream.  The “value” of the drug is therefore enhanced, and the normal dopamine system is now replaced by one that is hyperactive, producing reinforcement due to elevated levels of dopamine. 

 

There are also genetic components that account for approximately 50% of addiction.  Therefore, the history of a persons family having problems with addiction is a good indicator of the person’s own propensity towards addiction.

 

Early exposure also releases dopamine more readily, therefore adolescents that receive prescription painkillers for dental procedures or surgical procedures are much more likely to develop addiction than adults.

 

Now, it is all really more complicated than the simple explanation above since dopamine has many different functions in the body and acts on many parts of the brain and nervous system.  Dopamine may not really always produce pleasure per se but may produce the sensation of being rewarded or more correctly, remembered by the brain.  But both positive and negative experiences can cause dopamine surges such as the recorded sounds of war can cause a dopamine spike in veterans even though the experience was a very bad experience.  The mesolimbic system with a subtype of receptors D2 are the main receptors producing addiction.  But dopamine blocking drugs do not stop drug induced “highs” and only certain types of dopamine producing drugs produce pleasure.

 

  A more technical view of addiction:  motivation, addiction, attention, and lust are all associated with the dopamine pathways in the brain called the mesolimbic pathway.   The pathway begins with the ventral tegmental area cells deep within the brain and travels to the nucleus accumbens and cerebral cortex.  During the course of drug abuse, alcohol, heroin, cocaine, and prescription opioids all increase the dopamine in the nucleus accumbens as a signal feedback for predicted rewards.  If you have used a needle and syringe for injecting heroin, then viewing a needle and syringe will start causing increases in dopamine as your brain predicts the reward of using heroin, but if you don’t actually get the heroin, the dopamine levels decrease causing a bad feeling.  But dopamine can also increase from PTSD when they have increased awareness or paranoia.  Therefore dopamine isn’t necessarily a “pleasure” drug as much as it is called salience.  Salience is a sign to the brain that something needs to be addressed or paid attention to, i.e. something that stands out.  The stronger and faster increase of dopamine in the nucleus accumbens (e.g. shooting up or smoking a drug compared with oral use) leads to addiction more quickly.   The nucleus accumbens is in the front of the brain beneath the cerebral cortex.  Once the rapid sensation of pleasure occurs, the hippocampus (at the bottom of the brain) and the amygdala respectively lay down memories of the satisfaction and creates a conditioned response to certain stimuli.  Dopamine increase in the brain by itself may signal pleasure or liking something but is not enough to cause addiction in most people.  The reward circuit can be activated by food or sex also, but addiction is not the usual outcome.  Addiction is an overloading of the reward circuit.  Repeated exposure changes the communication between the nucleus accumbens and the prefrontal cortex (planning and execution part of the brain) that alters the response from liking something to wanting it to drive us to go after it.  Over a time the addictive stimulus becomes less pleasurable due to tolerance, and the brain response of eliminating dopamine receptors (since 5-10 times the normal amount of dopamine is being produced with these stimuli).  This is like the brain turning down the volume of a loudspeaker when the noise becomes too loud.  With fewer receptors, the impact on the brains reward circuits are less, and the addict has to take more of the drug in order to obtain the same response.  This is called tolerance.  At this point, compulsion takes over.  As the pleasure associated with an addictive behavior or addictive drug begins to wane, the memory of the pleasure associated with the drug or activity is resident in the hippocampus, and then the amygdala creates a conditioned response to visual or auditory cues associated with the drug or the paraphernalia associated with the drug, causing craving. 

 

Therefore a former addict who sees a needle (even without the drug) may experience intense craving, causing a relapse from their sobriety.  This is called conditioned learning and explains relapses even years after their last exposure.

 

However the brain does need pleasurable stimuli, and just saying no (abstinence alone) rarely works due to the cravings that are engrained and initiated by cues, some of which may be on TV or seen on the internet. 

 

The way out of addiction involves replacing the excess stimulation of dopamine by drugs, the memory of the pleasure, and the compulsive craving when presented with cues is by using a more controlled stimulation of dopamine production that is a steady state (not the roller coaster of being out of drugs, going through withdrawal, and then seeking out drugs by whatever means necessary) and filling the life by cultivating diverse events.  This means for some Suboxone or other form of buprenorphine may be necessary for awhile but at the same time embracing social activities, music, sports, or anything that produces pleasure by activating the dopamine receptors in a much milder manner than is achieved by street drugs or prescription painkillers.  It seems the pleasure created by starting new hobbies and activities produce dopamine that is in lower amounts than drugs, but also occupies time that would otherwise be spent in craving.  This type of diversion of attention away from hard drugs is often effective especially if one avoids the strong cues that result in recidivism.  Some of these cues to avoid are association with people that used to sell you or give you drugs, avoidance of party situations that may have drugs, and the avoidance of cross addictive drugs.  For instance both alcohol and heroin stimulate dopamine to a moderately high degree.  Exchanging one addiction for another is not a viable answer, so avoidance of all addictive drugs including street drugs and alcohol are imperative if one wants to beat addiction.  The use of counseling can reinforce the beneficial behaviors and encode positive memories of useful activities that help displace the drug associated memories and compulsions.  It is also extremely important to recognize the extreme pleasure associated with addictive drugs is not sustainable, and most addicts to heroin long ago reached the point that they are not trying to “get high” any longer, but simply trying to avoid withdrawal symptoms.  

 

Finally, we have much yet to learn about addiction.  What is clear is that conquering addiction is rarely possible by “just say no” programs or abstinence programs alone.  We know that recognition that self-pleasure is not the most important issue that drives us is imperative.  We know retraining of the memories that are engrained with visual, olfactory (smell), and auditory cues is mandatory and the longer one avoids these cues the better.  We know the compulsivity and craving can be reduced by first using a lower steady dose of drug that activates dopamine at a lower level (Suboxone or equivalent).  We know engaging in social activities, even if not a social person, are critically important, especially filling empty time with doing something preferably in groups and in situations that do not reactivate cues.   There is a way out, but it is not quick or simple.  But it definitely is possible.