The connection between substance abuse and mental illness is complex and still the subject of scientific investigation. However, what the medical community can assure at this point is that both have underlying causes, such that one can often lead to the other.

As such, understanding how the two are defined can help you notice the correlation. Mental illness is a broad term encompassing conditions that alter mood and behavior. These changes can interfere with daily functioning. On the one hand, substance abuse is the excessive use of drugs and alcohol for purposes they’re not intended for. The two are connected in that substance abuse can also rewire a person’s mood and behavioral responses.

With so many components in common, read on to find out how and why they’re connected by looking at the common factors of both.

Co-Occurring Disorders

The are some medical conditions that are known to coexist at the same time. In other words, one can give rise to the other and produce overlapping symptoms. These are called comorbidities or co-occurring disorders. Mental illness and substance abuse disorder have been identified in many diagnoses as a type of co-occurring disorder. It can also be due to both of the conditions happening in the same area of the brain and its chemicals.

This connection is why rehab treatment is often combined for both substance abuse and mental illness. However, it can be difficult to diagnose this co-occurring disorder because symptoms of one could hide the other. In addition to this, diagnosis depends on an individual’s account of experiences and symptoms, which are difficult for one to distinguish. Both concern mood and behavior.

The theory around the dual disorder is that substance abuse correlates with mental illness because it changes cognitive function. The same can be said vice versa, such that mental illness can lead to substance abuse because the brain becomes addicted to the pleasurable ‘high’ sensation that can’t be commonly felt.

Impact On The Brain

Studies have shown that frequent substance use and eventual abuse can alter the chemicals in the brain. It can also affect the brain’s structure, composition, and how it functions. This usually happens when drug use causes chemical imbalances by impacting the brain’s reward processing center.

When an illicit substance is used, it drastically increases the volume of neurotransmitters or chemical messengers of the brain for a short duration. Some of these include dopamine and serotonin, which are vital to regulating mood and emotions, as well as boosting feelings of pleasure, reward, and repeated motivating behaviors.

Overtime the brain loses its ability to produce or absorb these chemicals in normalized quantities. The result of this reduced amount of chemicals that are necessary for maintaining mental health can give way to mental illnesses.

Mental Illness Can Lead To Substance Abuse

Related to the point above, there are many parts of the brain that are affected by both substance abuse and mental illness. This is because the brain chemicals that are affected by substance abuse can be lessened by a mental illness. For instance, serotonin and dopamine can eventually be lowered by either drug use or psychiatric disorders, such as depression, or a combination of both.

Another common connection between substance abuse and mental illness is the condition known as self-medication. Many addiction studies support the theory that people with mental illness often resort to substance use to self-medicate.

This can be in the form drug taking due to mental illness, causing impaired judgement, or as a means to numb the dysphoria associated with being in a challenging mental state. Once substance use becomes the preferred method to cope with mental illness, it can then lead to abusing that medication.

Chronic Stress Disorders

Stress is a major leading cause of both substance abuse and the development of mental illness, particularly post-traumatic stress disorder. Moreover, commonly occurring stress is one of the reasons why individuals recovering from substance abuse are at risk of relapsing. This can be due to stress impacting parts of the brain that control motivation and impulsive behavior.

In a similar way, substance abuse can also impact how the body responds to stressful situations. It can intensify feelings of disordered panic, anxiety, and other mental illnesses. Stress can also modify dopamine functioning, which can incite the brain to revert to and enhance the cravings of previous drug usage. What’s more, since PTSD involves unwanted memories and flashbacks of traumatic events, drugs and alcohol are often used to desensitize one to the distress it causes.

Addiction And Dependence

Both addiction and dependence can be common connectors between substance abuse and mental illness. While addiction and dependency share similar characteristics, motive and severity differentiate them. When someone reaches an addiction stage, the biochemical changes are compromised, possibly for life. Feeding the substance abuse then becomes the main pursuit despite the willingness to stop, or awareness of the harm and behavioral effects it brings. It can, thus, be seen as the most severe stage of substance abuse disorder.

Some psychology experts have defined dependence more so related to a mental response to an unpleasant event and emotional state. There’s a varying degree of control, and using substances might not be a main priority. Instead, drug taking is used to manage triggers that offset the brain’s need for that substance. Such cases could be using alcohol whenever feelings of anxiety come up and one has to drive. A negative incident surrounding driving would then activate the dependency craving in the brain.

There’s currently a debate among neurologists and psychiatrists whether addiction and dependency should be classified as mental illnesses. Some scholars argue that due to their nature as ‘brain diseases,’ they should be approached and diagnosed similarly to mental illnesses. Others have pointed to drug addiction’s preventability, unlike some mental illnesses, making it a separate but linked medical condition.

Early Exposure To Substance Abuse

Exposure to drug use during the years of youth can also be directly linked to developing mental illness and substance abuse in adulthood. This influence is known as an environmental factor that contributes to a cycle of substance abuse and mental illness within families. What this means is that if a child or teenager witnesses a parent or guardian abusing substances, like tobacco, drugs, or alcohol, it increases the risk of them doing the same thing. They can subconsciously learn that these substances are acceptable items that can help them attain satisfaction.

This can also be related to a child experiencing a traumatic childhood. In this case, it can be incidents wherein violence, abuse, fear, loss, disasters are part of a normalized living situation. These experiences can then lead to drug taking by children and teens as a coping mechanism for negative home life.

The early exposure to substance abuse impacts the still developing adolescent brain. Mental illness can then become more prevalent as time goes on.

Genetic Vulnerability

Aside from family observation as an environmental factor, there are also genetic components that connect both substance abuse and mental illness. Ongoing research suggests that some people are more susceptible to both substance abuse and mental illness due to the presence of inherited traits passed through the family. About 40-60% of this vulnerability is attributed to dominant genotype.

The genetic element can present itself in the form of brain chemical deficiencies. If someone lacks a suitable amount of certain chemical receptors as a hereditary feature, it increases vulnerability. This has been discovered in some cases wherein individuals lacked dopamine receptors, and, thus, have a reduced capacity to feel pleasure. Such individuals are more likely to engage in pleasure seeking practices, such as substance abuse, to make up for this.

Other genetic influences may involve the brain regions that control behaviors, like impulsiveness, reward seeking, and how people uniquely respond to certain medications.

The Influence Of Physical Health

The state of an individual’s physical health can also affect the risk of developing substance abuse and, later, mental illness. This is mainly due to physical illness requiring a recurring intake of medication, especially for long-term conditions, like heart disease and cancer. In some circumstances, constant use of medication can become a gateway to using other substances, or may lead to dependence.

Physical health issues, such as chronic pain, have a complex relationship to both substance abuse and mental illness. Many medications, including alternative medicine like cannabidiol, are used to ease pain intensity, and may contain addictive substances.

Such is the case of patients who end up using and eventually abusing prescribed opioids and marijuana, whether legal or unauthorized. The frequent usage of high doses of marijuana has been linked to poor mental health. Additionally, being physically unwell can put individuals in an uncomfortable emotional state. Thus, substance abuse is used to suppress symptoms and bouts of illness.

Economic Status

Poverty or low socio-economic status is another factor that can connect substance abuse and mental illness. It can be due to the prevalence of illicit substances in lower-income communities and the lack of access to quality healthcare. The healthcare issue, in particular, can result in mental illnesses going untreated and undiagnosed. Individuals, sometimes, then rely on substances to substitute the medical care and social support they aren’t getting.

Furthermore, experiencing poverty can also cause a previously identified connection between drug use and mental illness, which is stress. Persistent worrying about survival and affording a basic living increases stress and the temptation to turn to substance use as a form of escapism. It should be said, however, that lower economic status only increases the risk factors. Substance abuse and developing mental illness later on can affect anyone, including affluent people in any society.

Existing Mental Health

Mental health measures the state of one’s mental wellbeing. It can be placed on a spectrum, from mental wellness to mental illness. This status can then impact the likelihood of turning to substance use or developing a mental illness.

If a relatively mild mental health condition is present and left untreated, it can develop into a more severe issue. In some cases, it’s drug abuse that causes this worsening mental health. For instance, if an individual with depression overuses psychotropic drugs, it can later advance into schizoaffective disorders. These drugs include cannabis, LDS, and amphetamines. The class of schizoid-related mental health disorders is considered to be some of the most critical mental illnesses.

In the case of ADHD, the medication used within treatment contains amphetamines. This central nervous system stimulant has shown results of improving brain development and stabilizing mood for better cognitive function. So, when patients or recreational users overuse amphetamines for a long time, it can then lead to a substance abuse habit. This reason is why there’s strict regulation of ADHD medications and doses.

Social Stigma

The social stigma associated with mental illness still remains pervasive among most societies. A lack of knowledge and exposure to mental health education has kept mental illness relatively misunderstood and mysterious. In the absence of scientific explanations, many cultures have created harmful myths and stereotypes surrounding mental illness, which makes it more challenging for patients to seek help.

Pople with mental illness are, thus, socially outcast and discriminated against. Some then turn to using substances to get the fulfillment denied to them by the society. The fear of social stigma and facing violence by an uncompassionate society can also contribute to prolonged substance abuse. Cultural beliefs about self-responsibility and blameworthiness are also factors.

Individuals are unlikely to undergo treatment due to low self-worth and lack of social support that could encourage hope in getting better. Due to this, mentally ill individuals can start to believe that they’re stuck in a situation that can’t be fixed.


Substance abuse and mental illness are connected because they can both affect the same parts of the brain. Additionally, genetic, socio-cultural, and environmental factors contribute to the presence of one, which increases the risk of developing the other.

Self-medication and escapism are the main reasons why individuals with mental illness turn to substance abuse. In turn, substance abusers can develop mental illnesses with overlapping symptoms after prolonged use.

These are the conditions that tie the two medical situations together. It’s important to remember that people’s circumstances are distinct from one another, so not all cases will involve the existence of both conditions.


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