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Cannabis (Marijuana) Use & Psychosis: Does It Increase Risk? (2023 Evidence Review)

The relationship between cannabis (marijuana) use and psychosis has been a topic of considerable scientific interest and public health concern.

With changing legal statuses and societal attitudes towards cannabis use in many countries, understanding this relationship is more critical than ever.


  • Systematic reviews and meta-analyses show a consistent association between cannabis use and increased risk of psychotic-like experiences and schizotypy.
  • Evidence is less conclusive regarding the impact of cannabis use on the progression from a clinical high-risk state to psychosis.
  • Cannabis use in the general population is associated with the development of clinical psychosis, with varying degrees of risk based on usage patterns.
  • The role of cannabis in exacerbating symptoms in patients with established psychosis is complex, with mixed evidence from systematic reviews.

Source: Psychiatry Research (2023)

Cannabis (Marijuana) vs. Psychosis & Schizophrenia

Subclinical Psychotic States

Subclinical psychotic states, including psychotic-like experiences and traits of schizotypal personality, present a fascinating area where cannabis use has shown significant associations.

Systematic reviews and meta-analyses indicate that cannabis users, particularly in the general population, exhibit a higher prevalence of these subclinical symptoms.

These experiences, while not reaching the threshold of clinical psychosis, are noteworthy for their potential to provide early indicators of susceptibility to more severe psychotic disorders.

Cannabis-Induced Psychosis

Cannabis-induced psychosis emerges as a specific clinical presentation, characterized by hallucinations, delusions, and disorganized thinking, typically triggered following cannabis use.

This condition is often temporary, yet it raises critical questions about the role of cannabis in precipitating acute psychotic episodes.

The link between cannabis-induced psychosis and the development of chronic psychotic disorders, such as schizophrenia, remains a subject of ongoing research, with current evidence suggesting a possible progression in some individuals.


The relationship between cannabis use and schizophrenia is complex and multi-dimensional.

Reviews have consistently demonstrated that cannabis use, especially during adolescence, is associated with an increased risk of developing schizophrenia.

This risk appears to be dose-dependent, with heavier and more frequent use linked to a greater likelihood of developing the disorder.

However, the question of whether cannabis use is a direct cause of schizophrenia or merely accelerates the onset in predisposed individuals remains under investigation.

Cannabis-Related Psychosis (Possible Mechanisms)

Neurochemical Changes: Cannabis primarily affects the brain’s endocannabinoid system, which plays a role in mood regulation, cognition, and behavior. THC, the psychoactive component of cannabis, can disrupt neurotransmitter systems, notably dopamine, which is closely linked to psychotic symptoms.

Altered Brain Development: In young users, cannabis can interfere with brain development, particularly in areas like the prefrontal cortex, critical for judgment and decision-making. This disruption can heighten vulnerability to psychotic disorders.

Sensitization & Increased Vulnerability: Regular cannabis use can lead to sensitization, where the brain’s response to cannabis becomes exaggerated over time, potentially leading to an increased risk of psychotic episodes.

Psychological Stress and Acute Intoxication: Cannabis use can induce acute psychological stress and transient psychotic symptoms, which, in susceptible individuals, might progress to more persistent psychotic states.

Interaction with Environmental Stressors: Cannabis use can interact with other environmental stressors (like trauma or social adversity), exacerbating their impact on mental health and potentially triggering psychosis in predisposed individuals.

Cannabis Use & Psychosis Link (2023 Umbrella Review)

Groening et al. synthesized the current best evidence on the effects of cannabis use on psychosis-related outcomes and moderating factors across the psychosis continuum.

It targeted evidence from systematic reviews and meta-analyses of observational studies to investigate the association between recreational cannabis use and persistent psychosis-related outcomes.


  • The review employed an umbrella review approach, systematically searching databases like Web of Science and Medline to identify relevant systematic reviews or meta-analyses.
  • The AMSTAR-2 tool was used for quality assessment.
  • The study focused on observational studies, acknowledging their limitations in establishing causal inferences but recognizing their value in representing the best available evidence.


  • Association with Psychosis Continuum: Cannabis use was associated with subclinical psychosis states and traits in the healthy population and was linked to the earlier onset and development of psychosis. However, it was not significantly associated with the Clinical-high-risk state for psychosis, nor with attenuated symptom severity or transition to psychosis in this group.
  • Relapse in Psychosis Population: An association was found between cannabis use and relapse in individuals with psychosis, but not with symptom severity.
  • Need for More Research: The review highlighted the necessity for more primary studies, especially large-scale genetic and epigenetic studies, to define the interplay between cannabis use and other environmental and genetic factors.


  • Quality of Systematic Reviews & Meta-Analyses: Many included reviews were rated as critically low in methodological quality, limiting confidence in their conclusions.
  • Focus on Observational Studies: The reliance on observational studies restricts the ability to make causal inferences about the relationship between cannabis use and psychosis-related outcomes.
  • Inconsistencies in Terminology & Measurement: Variations in terms used to describe psychosis-related outcomes and their measurement tools across studies pose challenges in synthesizing and interpreting the evidence.

Advanced Findings: Cannabis & Psychotic States (2023 Review)

1. Association with Subclinical Psychosis States & Traits

  • Healthy Population: A notable correlation was found between cannabis use and the presence of psychotic-like experiences (PLEs) and schizotypal personality traits. This relationship was observed across different studies with varying methodologies, suggesting a robust association.
  • Effect Sizes: For instance, odds ratios (OR) for the incidence of PLEs ranged from 1.75 to 1.77, while prevalence rates showed higher ORs, between 2.51 to 2.59.
  • Causality Considerations: Most studies were cross-sectional, limiting the ability to infer causality. The possibility of reverse causation, where individuals with PLEs might use cannabis as self-medication, was also discussed but not conclusively established.

2. Cannabis Use & Clinical-High-Risk State for Psychosis

  • CHR State Association: Contrasting findings were observed regarding cannabis use and the development of a clinical-high-risk (CHR) state for psychosis. Some studies found no significant association, while others suggested a potential link, particularly in the context of cannabis use disorder.
  • Mixed Evidence: For example, one meta-analysis found no significant association between current cannabis use and CHR state (OR 1.56), while another indicated a strong association with current cannabis use disorder (OR 5.49).

3. Cannabis Use & Relapse in Psychosis

  • Increased Risk of Relapse: Evidence more consistently indicated an association between cannabis use and an increased risk of relapse in individuals with established psychosis.
  • Symptom Severity: The relationship between cannabis use and symptom severity in psychosis was less clear, with some studies showing an increase in symptoms, while others did not find significant differences.

4. Methodological Considerations in Studies

  • Quality and Risk of Bias: The overall methodological quality of the included reviews varied significantly, with many studies rated as having critically low methodological quality. This aspect highlights the need for more rigorously conducted systematic reviews and meta-analyses in the field.
  • Observational Nature: The reliance on observational studies presented a limitation in establishing causal relationships. There was a notable absence of randomized controlled trials or longitudinal studies with advanced analytical methods, which could provide more robust evidence.

5. Genetic & Environmental Factors

  • Moderating Factors: The review pointed out the need to understand better the role of genetic and environmental moderators in the relationship between cannabis use and psychosis-related outcomes. This aspect includes factors like the age of onset of cannabis use, frequency and potency of cannabis, and individual genetic predisposition.
  • SNPs as Potential Moderators: Specific single nucleotide polymorphisms (SNPs) in genes like DRD2 and AKT1 were suggested as potential moderators, although these findings need further corroboration through more extensive genetic studies.

Risk Factors for Psychosis Onset from Cannabis

  • Mental Illness History: Individuals with a personal or family history of mental illness, especially psychotic disorders, face a higher risk. Cannabis can worsen latent symptoms or hasten the onset of psychotic conditions in these individuals.
  • Genetic/Polygenic Risks: Genetic predispositions significantly influence the impact of cannabis on mental health. Certain genetic profiles, particularly those linked to the dopamine system, can increase the risk of psychosis post-cannabis use.
  • Type of Cannabis/Potency/Frequency of Use: The risk varies across cannabis types. High-potency strains, especially those high in THC, are more closely associated with psychosis. Frequent and intense use intensifies this risk.
  • Adolescent Use: Early use of cannabis during adolescence, a critical period of brain development, can significantly raise the risk of developing psychosis later in life.
  • Comorbidity with Other Substance Use: The risk of psychosis is compounded when cannabis use is combined with the use of other substances, such as alcohol or psychoactive drugs.

Individuals At-Risk for Psychosis Should Avoid Cannabis

For those at risk of psychotic disorders – due to genetic predisposition, family history, or early mental health issues – avoiding cannabis is advisable.

The potential for cannabis to trigger or exacerbate psychotic symptoms in these groups is significant.

Abstaining from cannabis forms a key part of preventive strategies, particularly for those with identifiable risk factors.

Such an approach is in line with broader goals of reducing the incidence and impact of severe mental health conditions on individuals and society.

This precautionary measure is especially crucial for adolescents and young adults, where the risk of cannabis-induced psychosis is notably higher.

Clinical Considerations: Cannabis & Psychosis

  1. Screening for Cannabis Use: Clinicians should routinely screen for cannabis use in patients presenting with psychotic-like symptoms, especially in youth and young adults, given the association between cannabis use and subclinical psychotic states.
  2. Risk Assessment for Cannabis Use: It’s crucial to assess the risk of cannabis use in individuals with a family history of psychotic disorders or those who exhibit schizotypal personality traits. These individuals may be particularly vulnerable to the psychotogenic effects of cannabis.
  3. Counseling on Cannabis Risks: Patients, especially those at high risk for psychosis or with established psychotic disorders, should be counseled about the potential risk of cannabis use exacerbating psychotic symptoms or increasing the likelihood of relapse.
  4. Consideration of Environmental & Genetic Factors: Clinicians should consider environmental and genetic factors that may moderate the relationship between cannabis use and psychosis. This includes assessing the age of onset of cannabis use, frequency, and potency, as well as exploring any family history of psychiatric disorders.
  5. Intervention & Treatment Strategies: For patients with co-occurring cannabis use disorder and psychotic disorders, integrated intervention strategies that address both conditions are recommended. This may include psychoeducation, cognitive-behavioral therapy, and, where appropriate, pharmacological interventions.
  6. Monitoring & Follow-Up: Regular monitoring and follow-up are advised for patients with a history of cannabis use and psychotic disorders, to detect any signs of relapse or worsening of psychotic symptoms promptly.

Is it Possible to Reverse Cannabis-Induced Psychosis?

The question of whether cannabis-induced psychosis is reversible or leads to permanent psychiatric conditions has been a subject of significant research and debate.

The outcomes can vary depending on several factors, including the individual’s underlying mental health, the pattern and potency of cannabis use, and timely intervention.

Transient vs. Persistent Psychosis

Transient Psychotic Episodes: In many cases, cannabis-induced psychosis presents as a transient episode. This means that the psychotic symptoms — such as hallucinations, delusions, and disorganized thinking — emerge shortly after cannabis use and typically resolve within days or weeks once the effects of the drug wear off.

Risk of Persistent Psychosis: However, there is evidence suggesting that in some individuals, especially those with underlying risk factors like a family history of psychotic disorders or pre-existing mental health conditions, cannabis-induced psychosis may precipitate the onset of a more persistent psychotic disorder, such as schizophrenia.

Cannabis Potency & Usage Patterns

High-potency cannabis, particularly strains with a high THC to CBD (cannabidiol) ratio, is more strongly associated with psychotic episodes.

Chronic and heavy use of such cannabis increases the risk of developing persistent psychotic symptoms.

Early initiation of cannabis use, particularly during adolescence, is another risk factor.

The developing brain is more susceptible to the adverse effects of cannabis, potentially leading to long-lasting changes in brain function and structure.

Treatment & Prognosis

Immediate cessation of cannabis use is crucial. Studies indicate that individuals who stop using cannabis after a psychosis episode generally have a better prognosis.

Treatment with antipsychotic medication and psychotherapy can be effective in managing acute symptoms. Early intervention is key to preventing the progression to a more severe and enduring psychotic disorder.

Continuous monitoring and support are essential, as individuals who have experienced cannabis-induced psychosis may have an increased vulnerability to future psychotic episodes, particularly if they resume cannabis use.

Role of Individual Factors

The reversibility of cannabis-induced psychosis can also depend on individual factors like the person’s genetic makeup, overall mental health status, and the presence of supportive social and environmental factors.

Some individuals may experience full recovery from psychotic symptoms with no subsequent psychiatric issues, while others may develop a chronic condition requiring long-term management.

Takeaway: Cannabis vs. Psychosis (Complex Links)

The relationship between cannabis use and psychosis is complex, characterized by correlations that do not straightforwardly imply causation.

Evidence suggests that cannabis use is associated with an increased risk of subclinical psychotic states and may exacerbate symptoms in individuals with established psychotic disorders.

However, the direction of this relationship is not entirely clear, and it’s plausible that certain individuals may be genetically predisposed to both cannabis use and psychosis.

This ambiguity necessitates a cautious approach in clinical settings, emphasizing the importance of screening, risk assessment, and patient education.

Clinicians must consider individual patient factors, including genetic and environmental risk modifiers, in their treatment and counseling strategies.

Future research should focus on disentangling the causative links and exploring the intricate interplay between genetic predisposition, environmental factors, and cannabis use in the context of psychosis.


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