Schizophrenia And Substance Abuse


Definition of schizophrenia and substance abuse

Schizophrenia is a profound and enduring mental health condition that significantly impacts an individual's emotions, thoughts, and behaviours. When people think of schizophrenia, they usually think of a person experiencing hallucinations, and whilst this can be a symptom of schizophrenia, there are many other possible symptoms; delusions, thought insertion or broadcasting and disordered thoughts. Additionally, individuals with schizophrenia may exhibit blunted or inappropriate emotional responses, mood fluctuations, or attachment issues.

The WHO (World Health Organisation) defines substance abuse as “the harmful or hazardous use of psychoactive substances, including alcohol and illicit drugs”.1 These substances can be consumed for various reasons, but they are considered substance abuse when their consumption reaches a level that becomes harmful or hazardous.

Importance of understanding the relationship between schizophrenia and substance abuse

Frequently, individuals with poorly managed schizophrenia may resort to substance abuse as a means of self-medication or to cope with the anxiety and depression that often accompany the symptoms of schizophrenia.

On the other hand, while substance abuse doesn't directly lead to a diagnosis of schizophrenia, research has shown an elevated risk of developing schizophrenia in individuals with substance abuse issues. Numerous studies have indicated a connection between substance abuse and a higher likelihood of developing this mental health condition.

It is crucial to acknowledge that a diagnosis of schizophrenia cannot be given to someone under the influence of substances or due to a transient psychotic episode triggered by substance use. Although the symptoms may initially seem similar following ingestion, they differ primarily in terms of sudden onset and duration.

Schizophrenia and substance abuse: Prevalence and risk factors

Prevalence of substance abuse in individuals with schizophrenia

The prevalence of substance abuse in individuals with schizophrenia varies significantly across studies. The prevalence ranges from 10% to as high as 70%, depending on several factors such as how the diagnosis was made and the historical factors of the individual.2 In recent years, an increasing number of publications suggest a higher prevalence rate, with over 50% of individuals with schizophrenia experiencing substance abuse problems. Of particular concern is the impact of cannabis use, which has been identified as a significant contributing factor to relapses and challenges in treating schizophrenia. Studies have highlighted the adverse effects of cannabis on individuals with schizophrenia, making it a major concern in their management and treatment.3

Risk factors contributing to substance abuse in individuals with schizophrenia

It is established that a high prevalence of people with schizophrenia has substance abuse problems. The reasons for this vary widely depending on the person. Numerous individuals with schizophrenia may refrain from seeking mental health services due to various reasons, such as a lack of trust in available services, a preference for immediate relief of symptoms, feelings of isolation, and other personal factors. In their search for quick and easy relief from anxiety or depression, some may turn to illicit substances as a means of coping.

Also, an individual may have developed either a physical or psychological dependency and this could lead them to be reluctant to stop taking substances that could maintain or worsen their symptoms and condition.

Individuals with schizophrenia may grapple with unresolved issues like grief or childhood trauma, and they may perceive alcohol and illicit substances as more effective in temporarily managing their emotions. However, it's essential to note that these substances provide only short-term relief and can potentially exacerbate the challenges associated with schizophrenia in the long term.

By the time someone contacts mental health services, there is a high likelihood that they have already engaged in some form of substance abuse, thus making diagnosis and treatment more complex.

The relationship between schizophrenia and substance abuse

Effects of substance abuse on symptoms of schizophrenia

Substance abuse can diminish the effectiveness of the antipsychotic medication, leading to a worsening of symptoms. Stimulants and alcohol can also exacerbate aggression or violence, particularly when combined with distressing symptoms like delusions or hearing voices. Substance abuse may lead to reduced engagement with mental health and substance support services, as well as noncompliance with prescribed medication among individuals with schizophrenia. Moreover, when substance abuse coexists with schizophrenia, there is a higher likelihood of more frequent hospitalizations in mental health facilities. The risk of suicide escalates when individuals with schizophrenia are under the influence of substances, further highlighting the potential dangers associated with this combination of factors.2

Effects of schizophrenia on substance use and effects

The main effect that schizophrenia has on substance abuse is the desire to self-medicate in order to reduce the symptoms experienced.

Poorly managed schizophrenia leads to isolation, poor cognition and poor social functioning, which makes it more difficult for the affected individual to engage properly with mental health services, potentially increasing their accessibility to substances. 

Bidirectional relationship between schizophrenia and substance abuse

Substance abuse can exacerbate the symptoms of schizophrenia, and as these symptoms worsen, individuals may become less likely to engage with medication and support services. This, in turn, can lead to a continuous or escalated pattern of substance abuse, creating a cycle of deterioration. Without adequate support, the individual's condition progressively worsens.

Individuals in this situation often only seek help from mental health services when their symptoms and the impact of substances on their behaviour present a clear risk to themselves or others. For instance, an increased risk of violence may become apparent due to the combined effects of deteriorating symptoms and substance use. Addressing this cycle and providing appropriate support is crucial to improving the well-being and outcomes of individuals with schizophrenia and substance abuse issues.

Treatment options

Challenges in treating co-occurring schizophrenia and substance abuse

By the time someone with schizophrenia contacts mental health services, they may have a pre-existing substance abuse problem, which may include addiction or dependence. The addiction or dependence on substances can significantly contribute to a person's reluctance to discontinue their substance abuse.

This continued abuse of substances makes treatment extremely difficult. For example, a therapist would not allow a session to go ahead if someone was under the influence of substances.

The substances may interact negatively with the medication prescribed. For example, drinking alcohol on antipsychotic medications can increase side effects such as dizziness and drowsiness. This increased level of sedation could endanger the individual’s life. In general, taking illicit substances alongside prescribed antipsychotics will reduce the effectiveness of the medication, leading to the perception that the treatment is ineffective. 

Integrated approaches to treating co-occurring schizophrenia and substance abuse

Treatment for schizophrenia involves a combination of therapies such as CBT and antipsychotic medication to help improve outcomes. This can happen as an outpatient, or, if the degree of your symptoms or substance abuse means that treatment in the community is not possible, then an inpatient admission to a psychiatric hospital may be needed. In either case, there would be a multidisciplinary approach, meaning that multiple professionals will be involved in your care. This will involve a team to help with mental health and a team that specialises in managing substance abuse.  

Medication options for treating co-occurring schizophrenia and substance abuse

In terms of antipsychotics, a study in 2014 found that Clozapine, Olanzapine and Risperidone were more effective than other antipsychotics in the treatment of schizophrenia with coexisting substance abuse. A subsequent study in 2018 found Clozapine and Olanzapine to be superior to Risperidone in polysubstance and cannabis users in schizophrenia.

In terms of substance abuse, medication may be needed to support the individual to cease the substance abuse. For example, someone who drinks alcohol to a dependent level could have seizures and there is a risk of death if they suddenly stop drinking alcohol, therefore they may need a detox in the hospital, where a course of benzodiazepine (sedative) medications such as Chlordiazepoxide and Diazepam could be prescribed. Individuals are prescribed Subutex for heroin addiction and Acamprosate for alcohol addiction. People who use cannabis or stimulants to manage anxiety or depression may benefit from a short course of benzodiazepines or antidepressants. 


Schizophrenia often coexists with substance abuse, estimated to be present in approximately 50% of cases. The combination of these mental health conditions creates complexities in treatment due to the challenging nature of poorly managed schizophrenia symptoms and the dependence on substances as a coping mechanism. Substance use can significantly interfere with the treatment of individuals with schizophrenia, either by diminishing the effectiveness of medication or impeding their engagement with mental health and substance abuse services.

To achieve the most effective treatment outcomes, mental health services need to collaborate with drug and alcohol services to create a tailored treatment plan for each individual. Mental health services will focus on medication and psychological therapies to produce the best results, while drug and alcohol services will address the underlying need or desire for substances and design a rehabilitation program to help the individual avoid reverting to substance use as a coping mechanism.

When these services work cohesively together, the individual feels well-supported, leading to increased willingness to engage with the offered support. As a result, individuals with schizophrenia can experience improved well-being, lead more fulfilled lives, and have reduced chances of relapse. Collaborative and holistic treatment approaches play a crucial role in managing coexisting schizophrenia and substance abuse effectively.


  1. Dixon L. Dual diagnosis of substance abuse in schizophrenia: prevalence and impact on outcomes. Schizophrenia Research [Internet]. 1999 Mar 1 [cited 2023 Apr 20];35:S93–100. Available from:
  2. Winklbaur B, Ebner N, Sachs G, Thau K, Fischer G. Substance abuse in patients with schizophrenia. Dialogues Clin Neurosci [Internet]. 2006 Mar [cited 2023 Apr 20];8(1):37–43. Available from: 
  3. Arranz B, Garriga M, García-Rizo C, San L. Clozapine use in patients with schizophrenia and a comorbid substance use disorder: A systematic review. European Neuropsychopharmacology [Internet]. 2018 Feb 1 [cited 2023 Apr 20];28(2):227–42. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Karl Jones

BA Hons in Learning Disability Nursing, Diploma in Mental Health Nursing (Oxford Brookes

Karl has 12 years of experience in learning disability and mental health nursing in a variety of
settings. He has worked predominantly in general hospitals specialising in suicide prevention and the
psychological impact on long term health conditions. Most recently he has worked as a clinical
educator in the field of mental health. He is currently focusing on writing as a career with the aim of
imparting his knowledge to a wider audience. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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