In 2020, over 1.5 million people had an opioid use disorder (OUD). One in five adults in the United States experiences some form of mental illness.[1,2] Mental illness and drug addiction commonly co-occur. About half of individuals with mental illness will also develop a substance use disorder, and half of those with a substance use disorder will also have mental illness.
The Connection Between Mental Health & Opioid Use
Of the nearly 39 million people in the United States with a mental health disorder, close to 20% also use prescription opioids, receiving nearly half of all opioids prescribed in the U.S. Mental health conditions increase the risk of developing OUD and vice versa.
When two disorders, such as OUD and a mental health disorder occur in the same individual, it is called “dual diagnosis”. Mental health and medical professionals recognize the importance of treating mental health disorders at the same time as substance use disorders. These disorders can often be complexly intertwined, and treating them at the same time is critical.
The following mental health disorders commonly co-occur with OUD and SUD:
Depression and OUD
Depression is a mood disorder of the brain involving brain chemicals and often genetic and environmental factors. It can cause feelings of sadness and poor motivation that interfere with daily life functioning. People with depression often turn to drugs as a form of self-medication to feel better, which raises the risk for developing a substance use disorder. Similarly, opioid use can lead to extreme mood swings and crashes when the drug wears off, which can cause depression. Depression and OUD commonly co-occur. Studies have shown as many as 41% of people with OUD also have a mood disorder.
Anxiety and OUD
Anxiety disorders also commonly co-occur with OUD, at rates as high as 43% in studies of people being treated for OUD. Similar to depression, anxiety is a disorder that can involve multiple genetic, environmental and biochemical factors that can increase the risk for substance use and abuse and therefore addiction. Close to one in three people with an OUD also experience either insomnia or anxiety.
OCD and OUD
OCD, or obsessive-compulsive disorder, includes obsessions (uncontrollable and recurring thoughts) and compulsions (repetitive behaviors). Risk factors for the disorder often overlap with risk factors for substance abuse and OUD. These include genetics, brain functioning, childhood trauma and environmental factors.
Personality Disorders and OUD
Among the various types of personality disorders, the most common to co-occur with SUDs are antisocial personality disorder and borderline personality disorder. It is estimated that somewhere between 34.8% to 73% of people being treated for addiction also have a personality disorder. Typically, the personality disorder is the primary condition, and the substance use disorder develops as a result.
Bipolar and OUD
Bipolar disorder is defined as having periods of both depression and mania. It is estimated that approximately 56% of people with bipolar disorder also have a substance use disorder at some point in their lifetime. Bipolar disorder can include significant and extreme mood swings, which can be made more extreme by concurrent use of substances such as opioids.
Effect of Mental Health on Opioid Use
We do not often think of opioids as psychiatric drugs, but we probably should. Opioids bind to opioid receptors in the brain and cause feelings of pleasure — the euphoric “high.” This can increase the amount of mood enhancers, or brain chemicals called neurotransmitters that are responsible for feelings of pleasure, such as dopamine, in the brain. Therefore, they very much change the brain’s chemistry, and, with long term use, can alter a person’s behavior and personality. We really should think of them not only as pain medications, but as psychiatric medications as well. In someone with an underlying mental health disorder, opioids can either ameliorate or exacerbate the symptoms of various psychiatric conditions. It is no wonder that mental health conditions and OUD are so often seen together. Effective treatment of one requires effective treatment of the other. 
Effect of Opioid Use on Mental Health
Opioids change the chemistry in the brain and interact with the pleasure and reward receptors. This can cause extreme highs when taking the drugs and significant lows when they wear off. Because opioids create what can be thought of as a “fake” or artificial “euphoria” or happiness, depression and anxiety conversely are common side effects of opioid withdrawal. Prescription opioid use has been frequently associated with an elevated risk for also developing major depression. The more regularly opioids are taken, the more they change cellular function over time. This can mean that a person can no longer easily feel pleasure without the opioid drug. This causes repetitive opioid use and the development of OUD.
Why OUD & Mental Health Are So Connected
OUD and mental health conditions are closely connected through a variety of factors, including the following:
Both addiction and mental health disorders are heritable conditions, meaning that they can be passed down through families through genetics. Genetic factors can also contribute to how a drug affects a person and how the body and brain will respond. Genetics alone do not cause either addiction or mental health conditions. However, they can predispose a person to both.
Brain Regions and Composition
Similar parts of the brain can be involved in both the onset of a mental health condition and the likelihood of developing an OUD. For example, reward circuitry and pathways may not function correctly in someone with a mental health disorder, and this can also contribute to a desire to use substances and continued substance abuse. Regions of the brain involved in impulse control and risk assessment can also be dysfunctional, predisposing a person to using drugs more often and also having a mental health disorder. Brain chemistry and abnormalities can contribute to both mental health issues and a higher risk for drug abuse and addiction.
Multiple environmental factors can contribute both to the onset of a mental health disorder and the likelihood of misusing opioids and developing an OUD.
Early Life Adversity (ELA)
(also known as adverse childhood events, or ACE) is a major risk factor for both OUD and comorbid mental health disorders. Trauma at a young age can disrupt the natural formation and development of the brain and reward processing. This disruption of brain circuitry increases the risk for OUD and co-occurring mental health conditions
How to Minimize Addiction Risk While Taking Opioids
Chronic pain is often a side effect of depression, and many people with mental illness have a medical need to take prescription opioids. It is important to be aware of the risks and to understand the elevated risks for OUD with mental health conditions. If a patient requires opioid medications, the prescription opioids should always be taken exactly as directed and under the supervision and direction of a trained medical professional. They should always be taken for as short a time as possible.
Benefits of Dual Diagnosis Treatment for Co-Occurring Disorders
Dual diagnosis treatment involves treating both disorders simultaneously in an integrated fashion to manage both mental health issues and co-occurring OUD at the same time. This can improve quality of life and lead to better treatment outcomes, including decreased hospitalization, increased stability, less potential for medication interactions, improved psychiatric functioning, higher rate of successful treatment, and reduced substance use.
With dual diagnosis, a patient should receive care for their mental health condition either from a primary care doctor or from a mental health professional, as well as for substance use disorder. Ideally, multiple providers involved in the patient's care will communicate with each other to help come up with the best treatment plan for the individual patient. Treatment often includes use of both medications and behavioral therapies. Behavioral therapies for dual diagnosis treatment of co-occurring disorders can help to teach coping, interpersonal, and management skills to improve treatment outcomes and elevate daily life functioning.
Mental Health & Opioid Use Disorder FAQs
How does opioid use affect mental health?
Opioid misuse can increase the risk for developing a mental health condition due to changes made in brain chemistry and functioning.
Can opioids cause mental illness?
Opioids do not cause mental illness when used as medically directed. Opioid use disorder and opioid misuse on a long-term basis can potentially lead to the development of anxiety or mood disorders.
What is the connection between mental health and substance use?
Mental health conditions and substance use share many overlapping risks and contributing factors that can raise the risk for developing one if the other is present. A mental health disorder raises the risk for substance abuse and vice versa.
Can I safely take opioids if I have a mental health condition?
Yes, opioids can be taken when medically directed and under strict directions from a trained professional. It is important to use these medications exactly as directed.
Which comes first: mental health conditions or opioid use disorder?
Either condition can precede the other and raise the odds of developing the other.
Can both mental health disorders and opioid use disorder be treated together?
Ideally, both of these disorders are treated with dual diagnosis treatment, which involves treatment of both the opioid use disorder as well as treatment for the mental health condition.
What is the best treatment for co-occurring disorders?
The optimal treatment method for co-occurring mental health disorders and opioid use disorder involves dual diagnosis treatment, often with several professional providers working in tandem as a team, as well as medications and behavioral therapy techniques.
Will long-term Medication for Addiction Treatment (MAT) work with a mental health disorder?
Yes, MATs including Suboxone, which contains a long-acting partial opioid agonist can be used safely when medically directed to treat co-occurring disorders. Medications will need to be managed to avoid potential medication interactions and complications. This should be overseen by a trained professional, and all medications need to be taken as directed.