Substance-related and addictive disorders are complex and often and can result in significant consequences for the individual. The biological processes that cause addiction involve the reward pathways in the brain.
These circuits provide rushes of positive feeling and feel-good chemicals to “reward” substance use.
The areas of the brain responsible for stress and self-control also undergo long-term changes during an addictive disorder. This contributes to on-going difficulties in abstaining from the addictive substance.
Drug use is often voluntary in the first instance. The development of a full addiction occurs through a variety of circumstances.
However, the brain changes during a substance-related disorder in ways that can take a long time to bring back to a healthy state.
A person whose brain’s reward circuitry has not altered as a result of addiction experiences positive feelings in relation to generally rewarding behaviors, such as exercising, being with family, or consuming delicious food. These should all make a person feel good.
This might motivate a person to repeat these behaviors and regain that positive feeling.
Substances produce a euphoric feeling by triggering large amounts of dopamine in certain regions of the brain responsible for the feeling of reward. Addiction occurs when the act of using a substance takes over these circuits and increases the urge to consume more and more of the substance in order to achieve the same rewarding effect.
A substance use disorder eventually no longer causes the same rewarding feelings that it once caused. However, if the person abstains from using the substance, they begin to feel symptoms of withdrawal, which can be extremely unpleasant.
The person often finds themselves using the substance just to feel “normal” — which generally means preventing the discomfort of withdrawal symptoms.
Using drugs and alcohol to moderate mood can also impair the functioning of the prefrontal cortex, a section of the brain that manages executive decision-making. This part of the brain should alert a person to the harmful consequences of such behavior, but addiction impairs its ability to carry out this function.
A combination of these three mechanisms and the risk factors for addiction can lead to the development of an addictive disorder.
Another clear contributor to addiction is the type of substance a person takes. For example, opioids are highly addictive as they target receptors in the brain directly.
Many maintain that marijuana is less addictive in terms of its chemical content, but, instead, targets the pleasure and reward centers of the brain. Further research is necessary to support these claims.
Many people metabolize drugs in different ways.
Some people, for example, do not require much alcohol to reach the point of intoxication. Others can seemingly drink vast quantities without feeling intoxicated.
This often relates to a combination of age, gender, body weight, and other factors.
As part of regularly consuming large amounts of a substance, the body may become accustomed to its effects and metabolize it more efficiently. The person may require increased amounts of the substance to achieve the same effect that smaller amounts of the substance used to create.
Medicine generally refers to this phenomenon as tolerance.
When tolerance increases alongside the need to take a substance to avoid withdrawal symptoms, it often indicates the onset of an addictive disorder. If a person does not receive treatment, it can lead to dangerous consequences.
Addiction develops when the urge to take a substance hijacks parts of the brain that reward behavior and provides benefits for the body.
Substance-related disorders also impact the area of the brain responsible for emotions and decision-making. Eventually, people end up taking a substance not to feel good, but to feel “normal” by prevention of withdrawal symptoms.
These can combine with existing risk factors, such as extreme stress, to produce the behaviors and physical effects of addiction.
Does addiction always involve changes in the brain?
Generally, if a person meets the diagnostic criteria of the DSM-5 for a particular substance use disorder, it is most likely that brain changes have probably already occurred.
We do know that the sooner a person receives treatment for a substance use disorder, the better the chance of recovery may be.
Brain changes that occur as a result of a substance use disorder may be permanent, but some improvement may occur with extended abstinence.
Research in this area is ongoing.