Elsevier

Medical Hypotheses

Volume 72, Issue 2, February 2009, Pages 220-222
Medical Hypotheses

Parasitic brain infection, endocannabinoids, and schizophrenia

https://doi.org/10.1016/j.mehy.2008.08.025Get rights and content

Summary

Cannabis use has often been associated with various forms of psychosis. Today it is well established that everyone produces marijuana-like compounds known as endocannabinoids. The endocannabinoid system is a homeostatic regulator of all body systems including the nervous system. As a result, imbalances in the endocannabinoid system have been considered as possible causes of various forms of mental illness and abnormal behavior. In this paper, a novel hypothesis is presented that suggests that an as yet undefined subset of schizophrenia is caused by an excess of endocannabinoids that are produced to protect the brain in response to infections by agents such as Toxoplasma gondii.

Section snippets

1. Introduction

Schizophrenia is a chronic debilitating condition affecting approximately 1% of the population [1]. It is characterized by disorganized thoughts, hallucinations, and delusions (positive form), and apathy and avolution (negative form). Similar symptoms result from cannabis use, which has often been associated with psychosis (Greek meaning diseased soul), and specifically schizophrenia [2] However, it is only in recent times that tools have become available to properly, scientifically evaluate

2. Hypothesis

There are a number of disparate observations regarding schizophrenia that may be integrated into a cohesive model based on immune imbalance. Firstly, there is a strong negative correlation between rheumatoid arthritis and schizophrenia [26], yet, a number of similarities between these diseases have been indicated [27]. Secondly, rheumatoid arthritis is associated with a Th1/17 pro-inflammatory cytokine bias [28]. The negative correlation between arthritis and schizophrenia implies that

3. Discussion

For decades marijuana consumption has remained the center of controversy. The discovery of the endocannabinoid system now provides a scientific foundation for examining this topic. A possible link between cannabis consumption and schizophrenia continues to fuel the controversy. Numerous hypotheses have been proposed in an effort to explain schizophrenia. Proposals regarding genetic and environmental factors, as well as age remain inconclusive. This paper presents a novel hypothesis that

Acknowledgement

The author would like to thank Dr. Mitch Earleywine for critically reading the manuscript.

References (31)

  • M. Cohen et al.

    Cannabis, cannabinoids and schizophrenia: integration of the evidence

    Aust NZ J Psychiat

    (2008)
  • D. D’souza et al.

    Blunted psychotomimetic and amnestic effects of delta-9-tetrahydrocannabinol in frequent users of cannabis

    Neuropsychopharmacology

    (2008)
  • T. Rubino et al.

    Long lasting consequences of cannabis exposure in adolescence

    Mol Cell Endocrinol

    (2008)
  • M. Di Forti et al.

    Cannabis use and psychiatric and cognitive disorders: the chicken or the egg?

    Curr Opin Psychiat

    (2007)
  • R. Melamede

    Endocannabinoids: multi-scaled, global homeostatic regulators of cells and society

    InterJ Complex Syst

    (2006)
  • Cited by (14)

    • Identification of potential biomarkers and their correlation with immune infiltration cells in schizophrenia using combinative bioinformatics strategy

      2022, Psychiatry Research
      Citation Excerpt :

      Abdolmaleky et al. (2019) used whole-genome expression microarrays and DNA methylation profiling of SCZ brain samples found that BMP signaling, glutamate signaling and TGFβ signaling, astrocyte and cerebral cortex development are significantly coordinately upregulated in SCZ, and lateralized expression and DNA Methylation of TGFB2 are absent in SCZ. For many years, that there has been a suggested link between schizophrenia and some pathogens, and the immune imbalance induced by brain-infection might be a possible cause for SCZ (Melamede, 2009). The interaction between innate and adaptive immune responses plays a key role in the recognition and control of B.pertussis infections, and B cells and CD4 T cells were the main effector cells for providing protection (Kapil and Merkel, 2019).

    • Neurobiological studies on the relationship between toxoplasmosis and neuropsychiatric diseases

      2015, Journal of the Neurological Sciences
      Citation Excerpt :

      Nevertheless, a recent study on mice shows no clear region dependent cyst distribution within the hippocampus or amygdala, implying that cysts do not directly cause behavioural changes by perturbation of the surrounding tissue [32]. Other effects are more intriguing (1) alteration of neurotransmitter pathways involving production of proteins homologous to aromatic amino acid tyrosine hydroxylase (TH) and (to) dopamine (DOPA) 2 receptor (D2R) with increasing DOPA synthesis and tryptophan (TRP) degradation and decreasing serotonin synthesis [33]; (2) induction of the immune response [33], and (3) induction of endocannabinoids through the brain cannabinoid receptor type 1 (CB1R) activity on basal ganglia, substantia nigra, globus pallidus, caudate nucleus, and putamen [34]. The first two events are still the most important events and will be discussed briefly.

    View all citing articles on Scopus
    View full text