Schizophrenia and substance use disorders commonly co-occur. Schizophrenia is a mental health condition that can impact every aspect of a person’s life. People with schizophrenia often see and hear things that are imagined or hold beliefs that are untrue. Some people liken schizophrenia to being in a maze of mirrors. You see reflections everywhere, but they’re not always real. Sometimes, it’s hard to tell which reflections are true and which ones are tricks of the maze. 

People with schizophrenia can struggle to distinguish between what’s really happening and what their mind is telling them. It’s like navigating a confusing and sometimes unsettling maze of perceptions and realities.

People with schizophrenia have a significantly higher risk of developing substance use disorder. Here, we will explore the connection between substance use disorder and schizophrenia and how you can support a loved one experiencing both conditions.

What are the symptoms of schizophrenia?

Common symptoms of schizophrenia include: ^[2]

• Hallucinations: seeing or perceiving things that do not exist.^[3] Hearing voices is one of the most commonly experienced types of hallucinations.^[4] 

• Delusions: false beliefs that are not based in reality.^[5] People with delusions may believe they are being stalked or harmed by another person. 

• Disorganized thinking and speech: Thoughts and speech may be jumbled, making little sense. They may stop mid-sentence, or speak “word salad”, combining words that make no sense.^[6] 

• Disorganized or unusual behaviors: They may repeat movements or have unusual posture or physical behavior.^[7] At times they might appear as if they are in a trance, not moving or responding to anything or anyone present.

These symptoms are categorized into two categories:

• Positive symptoms, which refer to changes in behavior like hallucinations and delusions. 
• Negative symptoms, referring to feelings of disconnect and withdrawal. A person may show little emotion and not engage in activities like seeing friends or personal wellness.^[8] 

Because of these symptoms, people with schizophrenia may struggle with daily activities, like going to school or work, managing their money or completing tasks like personal cleanliness. They may also have difficulty maintaining relationships with family and friends.^[9] 

Affecting less than 1% of the U.S. population, schizophrenia usually first appears between one’s teenage years and their early 30s (people assigned male at birth typically exhibit symptoms earlier).^[10] While the exact causes of schizophrenia are not entirely known, it’s believed that both biological and environmental factors contribute.  

Genetics are particularly responsible; a family history of schizophrenia means one is more at risk of having it.^[11] Researchers have recently uncovered specific gene variants that are linked to schizophrenia as well.^[12] Environmental factors also contribute, such as exposure to certain illnesses before birth.^[13] 

Schizophrenia is a chronic condition, meaning that it cannot be cured and usually requires lifelong treatment. However, treatment plans including antipsychotic medications and cognitive behavioral therapy are effective at managing schizophrenia symptoms for many people.^[14]

How is schizophrenia diagnosed?

Treatment outcomes are more optimistic the earlier schizophrenia is diagnosed. However, diagnosis can be difficult for several reasons:

• Schizophrenia shares symptoms with other mental health conditions like bipolar disorder, post-traumatic stress disorder, and depression, which makes it harder to properly identify the illness. Someone’s symptoms can also be related to schizoaffective disorder, which is a separate condition related primarily to mood.^[15]  

• It is particularly hard to diagnose teenagers, since some of the symptoms like trouble sleeping and isolation from friends and family may be typical behaviors at that age.^[16] 

• People with schizophrenia are also often reluctant to seek treatment or do not know or believe that they have it.^[17]

To be diagnosed with schizophrenia, a person must experience at least two schizophrenia symptoms over the course of six months.^[18] At least one of these symptoms needs to be related to psychosis, like delusions or hallucinations. 

To confirm a diagnosis, a physical examination and a mental health evaluation are completed. 

While there is no one test that can diagnose schizophrenia, doctors can use blood tests to screen for substance use and other conditions that can cause schizophrenia-like symptoms.^[19] An MRI scan or other form of imaging may also be performed to examine the brain structure.

How are schizophrenia and substance use disorder related?

People with schizophrenia may be at higher risk of developing a substance use disorder.

Research is limited, but generally implies that people with a psychotic illness use certain substances (namely alcohol, nicotine, cannabis, and cocaine) at much higher rates than the general population. In fact, some data suggest that nearly half of individuals with schizophrenia may experience problem substance use in their lifetimes.^[20] According to some studies: 

• Around 20-30% of individuals with schizophrenia may have an alcohol use disorder.^[21] Alcohol use disorder and schizophrenia also share certain genetic similarities.^[22]  

• As many as 60% of individuals with schizophrenia may smoke cigarettes.^[23]

• People with methamphetamine use disorder are at higher risk of schizophrenia.^[24] 

Like other co-occurring disorders, substance use may be seen as a way to cope with the distress that schizophrenia can cause. The symptoms of schizophrenia can be severe and interfere significantly with an individual’s quality of life; substances, for example, might be intentionally misused to quiet the voices a person hears or minimize hallucinations. Overall, however, substance use will only worsen these symptoms and negatively affect treatment.^[25] 

It is also important to note that some psychosis can be caused solely by substance use. This is referred to as “drug-induced psychosis.” For example, the use of substances like meth can mimic schizophrenia symptoms but might not be related to schizophrenia. 

Cannabis and schizophrenia

Marijuana (cannabis) use has been connected to developing psychosis. This is particularly worrisome because the average amount of THC in cannabis products has greatly increased over the past several decades. Using a cannabis product with a THC potency of over 15% is linked to a three-fold increase in the likelihood of experiencing mental health and other problems.  

Cannabis might lead to schizophrenia symptoms emerging earlier for people who have a genetic risk of developing schizophrenia.^[26]

The earlier one uses cannabis, the more likely they are to develop schizophrenia symptoms at a younger age. A recent study by the National Institute on Drug Abuse found a strong link between cannabis use disorder and schizophrenia among young men. It indicated that as many as 30% of schizophrenia cases may have been prevented had these individuals not initially developed cannabis use disorder.^[27]

Treating schizophrenia and substance use disorder

Co-occurring substance use disorders and schizophrenia can be quite difficult to treat. Substance use worsens mental health treatment outcomes. Patients are often not properly treated for both.  

Despite these difficulties, integrated treatment for schizophrenia and substance use disorder does exist and can have very positive outcomes.^[28] Treatment options include: 

Medications: Schizophrenia is primarily treated through a combination of antipsychotic drugs and therapy. These help a patient’s mood and can decrease hallucinations and delusions.^[29] Common medications to treat schizophrenia are usually split into two categories: 

• Typical/conventional antipsychotics – Also known as “first-generation” drugs, these refer to older medications that were first used to treat psychosis. They are used to help control the brain chemical dopamine and regulate mood. These include haloperidol (Haldol), chlorpromazine (Thorazine), and fluphenazine (Prolixin).^[30]

• Atypical antipsychotics – these “second-generation” medications are newer and are increasingly being used as a more common treatment for schizophrenia. These include risperidone (Risperdal), clozapine (Clozaril), and aripiprazole (Abilify).^[31] Another potential medication in this category is KarXT, a new and promising antipsychotic drug currently being reviewed by the FDA for approval.^[32] Atypical drugs are serotonin-dopamine antagonists, meaning they target another brain chemical, serotonin, as well. 

 Depending on the type of medication, it can be administered as a daily pill or as an injection that lasts longer. 

Both typical and atypical antipsychotic medications are very effective at treating positive symptoms like hallucinations and delusions. However, they can come with a host of serious side effects, like:  

• Dry mouth 

• Sedative effects (constant tiredness and lack of energy) 

• Dizziness 

• Low blood pressure 

• Weight gain and increased risk of developing diabetes 

• Blurred vision 

• Seizures 

One serious side effect associated with these medications is developing uncontrollable body movements, like flailing limbs and stiffness. However, the atypical medications generally cause fewer side effects than the typical medications and can be more effective at preventing these involuntary movements.^[33]

Some patients with schizophrenia may also be prescribed a mood stabilizer (ex. lithium) or an antidepressant (ex. fluoxetine) alongside their antipsychotic medications. Patients with schizophrenia may have anxiety and depression disorders that need to be treated as well.

Antipsychotic medications can be used together with medications to treat opioid use disorder (MOUD). In fact, some research suggests that these medications, such as buprenorphine, can have a positive effect on reducing schizophrenia symptoms without side effects.^[34] However, one study found that schizophrenia patients with a co-occurring substance use disorder are often not treated for their SUD with MOUD.^[35] Treating substance use disorder is a very important component of treating schizophrenia, given that each disorder can worsen the other’s symptoms. 

Therapies: Therapy is also typically part of the treatment plan for both schizophrenia and substance use disorder patients. Some forms that are effective include: 

• Cognitive behavioral therapy (CBT) is the most commonly used form of therapy for schizophrenia. It focuses on identifying and changing negative thought patterns and behaviors, developing coping skills, and preventing relapse. CBT can help patients cope with the significant stressors associated with the illness, like feelings of social isolation and side effects from treatment.^[36] 

• Family therapy includes a patient’s loved ones in treatment, acknowledging that mental health and substance use disorders impact the individual suffering and those around them. It can help family members better understand the disease and the behaviors of their loved ones to better support them. 

• Social skills training therapy helps patients improve their interpersonal relationships in order to better function in society.^[37] This can be particularly helpful for people with schizophrenia, many of whom have a lack of social skills because of their illness. Social skills training can help reduce everyday stressors and triggers that can impact symptoms, as well as in developing resilience and the ability to manage treatment on their own.^[38]

• Additionally, motivational interviewing, contingency management, and acceptance and commitment training have all also been found to be helpful therapies for treating psychotic symptoms, substance use and general functioning.^[39]  

Schizophrenia is a complicated illness, and, along with substance use disorder, can cause pain and suffering for you and your loved one. But there is hope. With your support and proper integrated treatment, people with these disorders can lead fulfilling and healthy lives.  

Start here for information on how to navigate the treatment system. To learn more about encouraging treatment and providing other support to your loved one, click here. And for assistance with where to start or help with developing a plan, please reach out to our support services here.