Substance use disorder is strongly connected with mental illness. The Substance Abuse and Mental Health Services Administration (SAMSHA) lists that 15.7% of the general population is likely to abuse or rely on substances. This number goes up to 36.7% for individuals with any mental illness and up to 49.4% for individuals with severe mental illnesses.
This overlap exists because of two primary reasons, with a great deal of interplay between many other contributing factors. For example, individuals who are most vulnerable to mental disorders are also most vulnerable to substance use disorders. For example, children with Adverse Childhood Experiences (ACE) are more vulnerable to mental illnesses such as depression and anxiety, are more vulnerable to substance use disorders, and are more likely to be in social and economic conditions that encourage or exacerbate substance use disorders.
Self-Medicating Existing Disorders
Self-medication is a phenomenon that contributes to a significant portion of addiction, because users develop substance abuse as a coping mechanism.
Here, individuals might drink, take a pill, or take more than their prescription to feel better. They haven’t been told to by a doctor and their “medication” is not regulated by anyone. This frequently leads to a pattern of escalation, because most substances result in tolerance and chemical dependence. Users have to increase their dose to reach the same effects, increasing the dose results in them feeling worse (hangovers, poor performance, less sleep) resulting in more stress or anxiety or depression, and more self-medication.
Many of these disorders cause intense mood changes, constant stress or distress, constant worry, feelings of hopelessness or inability to enjoy things, panic attacks, hallucinations, and other worse problems. Many result in social isolation, worsening anxiety, and increasing problems that escalate without treatment.
Individuals who use substances to self-medicate can typically temporarily alleviate these symptoms, feel better, feel like they belong, or simply forget everything.
Substance Abuse Exacerbates Symptoms
The second primary interplay between substance use disorder and mental illness is that substances can significantly exacerbate the symptoms of mental illness. This means that many people who start substance abuse without diagnosable mental illnesses may exacerbate those symptoms to the point of having a permanent condition. While it’s common to say “the substance caused the disorder” in these cases, the truth is much more often a complex interplay between existing mental states and vulnerabilities.
Many drugs directly exacerbate issues such as anxiety, depression, paranoia, and personality disorder. For example, emotional blunting is a common side-effect of using drugs that induce a high by affecting serotonin and dopamine receptors. Individuals who frequently use these drugs may struggle to feel anything at all.
Most mind-altering drugs, including alcohol, interact with receptors in the brain that influence how people think and feel. Over the long-term, the brain changes its production of these substances, typically reducing quantities of serotonin, dopamine, etc. This can actually cause depression and anxiety, although the results may vanish when individuals stop using.