Research has long shown a correlation between substance addiction and mental health. It is estimated that people diagnosed with mood or anxiety disorders are twice as likely to suffer from a substance use disorder, as well. The same is true for those with antisocial and conduct disorders. Similarly, individuals diagnosed with drug use disorders are about twice as likely to suffer from the above mental health conditions. In many ways, drug addiction and mental health relate. 

Both mental health disorders and substance use disorders develop within the brain. They affect similar parts of our brain chemistry, and have overlapping effects on our psychology and cognition. It is no wonder that more than 17 million adults in the United States are battling both substance addiction and a mental health disorder. The question remains, “Why?”

Why are mental health and substance addiction so connected? What factors are contributing to their relationship? How does addiction relate to our brain chemistry, and in turn disrupt our mental health? 

We answer these questions, and more, below.

How is Addiction Related to Brain Chemistry?

Substance addiction occurs after prolonged, repeated use of drugs and alcohol. As research tells us, drugs and alcohol are chemicals. When chemicals are introduced into our body, they enter the brain’s communication system and alter the way our nerve cells send, receive, and process information. This happens with immediate use. With prolonged use, drugs and alcohol make more lasting changes within the brain. They re-wire brain circuits and cause changes in neurons, creating dependency. Many repeated drug users will begin to rely on drugs to function, because of the adjusted signals occurring within their brain. 

Our brains are wired to repeat behaviors that we need to survive, like eating, or that make us feel good. The brain’s limbic system, and specifically “reward” circuit, regulates the emotional responses to these activities, and releases the neurotransmitter dopamine to create a sense of happiness and fulfillment. 

However, science shows that many drugs activate the brain’s “reward” circuit and trigger heightened surges of dopamine—more than what is naturally released. This causes euphoric effects or the “high” that drugs temporarily provide, and trigger our brain to want to repeat the drug use. The brain will send out intense signals to seek and use the drug again. When a person continues to use drugs, and loses control over their ability to make sound decisions regarding drug use, this indicates addiction. Substance addiction happens when a person continues to use drugs and seeks them compulsively, despite the negative effects that substance use has caused on their life. Teenagers are especially at risk.

However, this is not the only way that addiction affects our brain chemistry. Brain-imaging studies now show that repeated drug use will also cause disruptions in the brain’s frontal cortex. The frontal cortex is the part of the brain that regulates cognitive activities like decision-making, response inhibition, impulse control, planning, and memory. As stated by the National Institute on Drug Abuse (NIDA), “We now know that many of the drugs of abuse target not just those aspects of the brain that alter things like emotion, but also areas that affect our ability to control cognitive operations.”

Individuals who are struggling with drug addiction, therefore, will experience disturbances in their ways of thinking and behaviors. They may have impaired judgement, poor decision making, and an inability to control their impulses. They will prioritize obtaining and using the drug above all else. Compulsive drug seeking behaviors are a hallmark trait of addiction, which stems from these changes within the brain.

Which Areas of the Brain are Affected by Addiction and Mental Illness?

When a person repeatedly used drugs, there are three primary areas of the brain that are affected:

• The brain stem:

The brain stem regulates all the functions our body needs to survive, including breathing, circulating blood, and digesting food. It connects the brain to the spinal cord, and lets the brain know what’s happening to the body. Drugs affect the brain stem particularly in the case of an overdose which can halt life-sustaining functions.

• The limbic system:

As noted above, the limbic system is what control our emotional response to activities. For example, it releases dopamine when we eat, and motivates us to repeat this behavior because it is critical to our life. When drugs affect the limbic system, the brain starts to demand and rely on drugs.

• The cerebral cortex:

The cerebral cortex makes up about three-fourths of the brain, and has several different areas in which drugs might affect. These areas control specific functions. For example, the frontal cortex is the designated “thinking center.” It powers our ability to think, plan, rationalize, remember, solve problems, and make decisions. When drugs are repeatedly used, these cognitive abilities begin to weaken, and drug users have less control over their ability to think, plan, and make decisions. Some studies even show that drug use can decrease the amount of grey matter in the cerebral cortex.

Many of the above areas of the brain are also impacted by mental health disorders like depression, anxiety, and bipolar disorder. Scientists understand that mental illnesses are also associated with changes in neurochemicals, and specifically with problems in the brain’s communication system. When there are abnormal connections in the brain circuit, it can lead to issues with how the brain processes information. This can, in turn, result in abnormal mood, thinking, perception, and behavior. 

For example, studies of people with major depressive disorder have shown lower volumes of grey matter in brain areas like the prefrontal cortex—which is critical for cognitive control—as well as the hippocampus, the anterior cingulate cortex, and others. These individuals have also shown functional brain differences, such as reduced activation in the brain when anticipating or receiving a reward.

So, How Are Mental Health and Addiction Related?

Due to the overlapping nature of addiction and mental health disorders, the high rates of co-occurring disorders is not a surprise. Mental health and addiction often co-occur, largely due to their effects and risk factors within the brain. According to the National Institute on Drug Abuse (NIDA), there are three primary, causal relationships between mental health and addiction:

1. Common risk factors can contribute to both mental illness and substance addiction.

Mental health disorders and substance use disorders share many risk factors, or factors that can increase a person’s vulnerability to either type of disorder. For example, both could be triggered by:

• Genetic factors and family history
• Environmental factors, such as history of trauma, chronic stress, or abuse
• Epigenetic influences, which are a combination of gene and environmental causes

The NIDA also reports that “many areas of the brain are affected by both substance use disorders and other mental illnesses,” which may play a role in their co-existence. Specifically, the regions of the brain that mediate reward, decision-making, impulse control, and emotions may be disrupted by substance use disorders, depression, schizophrenia, or other psychiatric disorders. The NIDA also underlines the information above, stating, “Multiple neurotransmitter systems have been implicated in both substance use disorders and other mental disorders including, but not limited to, dopamine, serotonin, glutamate, GABA, and norepinephrine.”

2. Mental illness may contribute to substance use and addiction.

A common hypothesis about co-occurring disorders is that those struggling with mental illness will turn to drugs and alcohol to cope. This is referred to as “self-medication.” Drugs and alcohol may temporarily reduce the symptoms associated with a mental illness, and lead a person to keep using the drugs to feel better. However, over time, these drugs create changes in brain activity and can trigger a dependence. 

The NIDA reports that, when a person develops a mental illness, the changes in their brain can “increase the vulnerability for problematic use of substances by enhancing their rewarding effects, reducing awareness of their negative effects, or alleviating the unpleasant symptoms of the mental disorder.” However, over time, the use of drugs can exacerbate the symptoms of mental illness, and make a person feel worse. This is in combination with the effects of addiction, like increased drug cravings.

3. Substance use and addiction can also lead to mental illness.

Research has also showed us that repeated substance abuse can also contribute to the development of a mental illness. According to the NIDA, “Substance use can lead to changes in some of the same brain areas that are disrupted in other mental disorders, such as schizophrenia, anxiety, mood, or impulse-control disorders. Drug use that precedes the first symptoms of a mental illness may produce changes in brain structure and function that kindle an underlying predisposition to develop that mental illness.”

Mental Health, Substance Addiction, and the Brain

Both mental health disorders and substance use disorders are chronic conditions of the brain. They cause changes within the brain that affect their ability to think clearly, to make decisions, and to function in everyday life. The changes that happen within the brain can be long-lasting, and take time to heal from and overcome. Therefore, treatment for these disorders is not simple.

Although many assume substance addiction is a shortcoming, a choice, or a failure, they could not be farther from the truth. Science shows us that addiction is a disease of the brain. As explained to by A. Thomas McLellan, co-founder of the Treatment Research Institute, in an NPR interview:

“Emerging science shows this is a brain disease. It’s got the same genetic transmutability as a lot of chronic illnesses. And the organ that it affects is the brain, and within the brain it is motivation, inhibition, cognition, all those things that produce the aberrant, unpleasant behaviors that are associated with addiction.”

Addiction, in many ways, is a mental illness—and must be treated as such. Just like diabetes or hypertension, it needs to be actively managed for the rest of their life. It is not as simple as stopping drug use, just as it is not simple to overcome a mental health issue like depression or anxiety. These all require active, ongoing care. 

When both substance addiction and mental health disorders exist simultaneously, they must be treated in an integrated dual diagnosis treatment setting. This means that the disorders are treated as though they are in a relationship, and that the same team is working to manage and treat these disorders together. They are treated in the same place, as co-occurring disorders, rather than separate entities. Only a dual diagnosis treatment program can assist with this level of care.

A Note from Turnbridge

Just as the brain is a complex organ, mental health disorders and substance use disorders are equally complex. They require a high level of care and support throughout the treatment process. They require active and ongoing management. But both are manageable and treatable. Recovery is possible.

If you or a loved one is struggling with mental health, addiction, or a combination, do not be afraid to ask for help. There are treatment centers dedicated to cases like yours, who can help you overcome the difficult symptoms that these disorders have caused on your mental health and wellbeing. Contact Turnbridge at 877-581-1793 to learn about our dual diagnosis programs for teens and young adults.