Drug use disorders often coexist with other mental illnesses. Let’s explore the ‘why’!

Drug use disorders and mental illness go hand in hand, as people addicted to drugs have twice the risk of developing mood and anxiety disorders compared to people in general, and vice versa. According to the 2019 National Survey on Drug Use and Health (NSDUH), 24.5% (or 61.2 million adults) ages 18 and older experienced a mental illness (AMI) or substance use disorder (SUD) in the last year. Additionally, 16.8 percent (or 42 million people) had an AMI but not a SUD. The survey also reported a 3.9 percent (or 9.7 million people) incidence of SUD but not AMI, while 3.8 percent (or 9.5 million people) were found to struggle with both with AMI as with SUD.

Such a high co-prevalence of AMI and SUD makes us wonder if both things are interrelated and, if so, why?

Co-occurrence: One coincidence or more

The high incidence of substance use disorders and co-occurring mental illness is independent of a causal association between the two. Furthermore, it does not indicate any particular sequence in the onset of the problem, simply because multiple factors can contribute to SUDs and AMIs, most of them being independent of each other.

For example, it is important to see if the symptoms have progressed to a specific level (according to the DSM) to confirm the diagnosis of any mental disorder. However, subclinical symptoms can also lead to drug use. Although it is always difficult to know what comes first between AMI and SUD. Nevertheless. Three possibilities seem to exist.

• Drug use can lead to mental illness: The drug or drugs of use may be responsible for causing one or more symptoms of a mental illness in the user. Evidence supporting the possibility comes from the known association between increased risk of psychosis and marijuana in some users.
• Mental illness leading to drug use.: Researchers have been talking about the possible role of mental illness in causing drug use. People who report overt, mild, or even subclinical mental disorders are vulnerable to drug use as self-medication. Slowly, as the person feels more empowered by using the drug, they become dependent on it, leading to addiction.
• overlapping factors: There are certain factors, including genetic vulnerabilities, brain deficits, and/or early exposure to stress or trauma, that can cause both AMI and SUD.

These three scenarios can be expressed (to different degrees for different individuals) by presenting a case of concurrent AMI and SUD.

Exploring common factors

Genetics have a role to play in both an AMI and an LDS. Genetic factors may be a significant common link between these two conditions, which are known to contribute to the development of both addiction and other mental illnesses. According to researchers, genetics contribute 40-60 percent to a person’s vulnerability to addiction. At the same time, genes may also act indirectly to contribute to the development of SUD by altering an individual’s response to stress or one’s tendency to develop novelty-seeking and risk-taking behaviors.

Similar brain regions are involved. It may be more than coincidental that, in both SUD and AMI, the same brain regions are affected. For example, addictive substances and mental illnesses such as depression and other psychiatric disorders affect dopamine, a chemical that carries messages from one neuron to another.

This overlap of brain areas affected by AMI and SUD may indicate the possibility of some brain changes that can be caused by either of these and affect the other.

A report published in the National Institute on Drug Abuse (NIDA) suggests that the development of a mental disorder and subsequent changes in brain activity tend to increase a person’s susceptibility to substance use by reducing the awareness of its negative effects, amplify its positive effects, or alleviate the unpleasant effects caused due to the mental disorder.

Achieving mental health is about timely treatment

Different behavioral therapies have been found to be effective in the treatment of comorbid conditions. However, it is important to consider other associated factors, such as the age of the patients and the specific drug used, among other things, while continuing with the planned treatment.