“The study cohort comprised almost 600,000 patients each year, representing approximately 2.3% of the UK population aged 16 to 44. Between 1996 and 2005 the incidence and prevalence of schizophrenia and psychoses were either stable or declining. Explanations other than a genuine stability or decline were considered, but appeared less plausible. In conclusion, this study did not find any evidence of increasing schizophrenia or psychoses in the general population from 1996 to 2005.”
https://www.ncbi.nlm.nih.gov/pubmed/19560900
https://www.sciencedirect.com/science/article/pii/S0920996409002692?via%3Dihub
“The incidence and prevalence of patients showing schizophrenic syndromes are unchanged or have even fallen while the use of cannabis has increased enormously. We must conclude that either previous schizophrenic illnesses have become much less common or that cannabis schizophrenia is rare and perhaps it may not even exist.” https://www.bmj.com/content/325/7374/1183/rapid-responses
“Cannabis use appears to be neither a sufficient nor a necessary cause for psychosis.” https://www.ncbi.nlm.nih.gov/pubmed/14754822
“The current data do not support low to moderate lifetime cannabis use to be a major contributor to psychosis or poor social and role functioning in high-risk youth.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3459073/
“In agreement with the neurodevelopmental hypothesis of schizophrenia, prenatal exposure of rats to the antimitotic agent methylazoxymethanol acetate (MAM) at gestational day 17 produced long-lasting behavioral alterations such as social withdrawal and cognitive impairment in the social interaction test and in the novel object recognition test, respectively. At molecular level, an increased 
“Among the many cannabinoids in the cannabis plant, 
“Following the discovery of the endocannabinoid system and its potential as a therapeutic target for various pathological conditions, growing interest led researchers to investigate the role of cannabis and its derivatives for medical purposes. The compounds Δ9-tetrahydrocannabinol and 
“The chronic use of drugs that reduce the dopaminergic neurotransmission can cause a hyperkinetic movement disorder called tardive dyskinesia (TD). The pathophysiology of this disorder is not entirely understood but could involve oxidative and neuroinflammatory mechanisms.
“Schizophrenia is considered a debilitating neurodevelopmental psychiatric disorder and its pharmacotherapy remains problematic without recent major advances. The development of interventions able to prevent the emergence of schizophrenia would therefore represent an enormous progress.
Here, we investigated whether treatment with 
“Substance use may confound the study of brain structure in schizophrenia. We used voxel-based morphometry (VBM) to examine whether differences in regional gray matter volumes exist between schizophrenia patients with (n = 92) and without (n = 66) clinically significant 
“Approximately 0.5% of the population is diagnosed with some form of schizophrenia, under the prevailing view that the pathology is best treated using pharmaceutical medications that act on monoamine receptors.
We briefly review evidence on the impact of environmental forces, particularly the effect of autoimmune activity, in the expression of schizophrenic profiles and the role of Cannabis therapy for regulating immunological functioning.
A review of the literature shows that phytocannabinoid consumption may be a safe and effective treatment option for schizophrenia as a primary or adjunctive therapy.
Conclusions: Emerging research suggests that Cannabis can be used as a treatment for schizophrenia within a broader etiological perspective that focuses on environmental, autoimmune, and neuroinflammatory causes of the disorder, offering a fresh start and newfound hope for those suffering from this debilitating and poorly understood disease.”
“Mental disorders have a high prevalence compared with many other health conditions and are the leading cause of disability worldwide. Several studies performed in the last years support the involvement of the endocannabinoid system in the etiopathogenesis of different mental disorders.
The present review will summarize the latest information on the role of the endocannabinoid system in psychiatric disorders, specifically depression, anxiety, and schizophrenia. We will focus on the findings from human brain studies regarding alterations in endocannabinoid levels, cannabinoid receptors and endocannabinoid metabolizing enzymes in patients suffering mental disorders.
Studies carried out in humans have consistently demonstrated that the endocannabinoid system is fundamental for emotional homeostasis and cognitive function. Thus, deregulation of the different elements that are part of the endocannabinoid system may contribute to the pathophysiology of several mental disorders. However, the results reported are controversial. In this sense, different alterations in gene and/or protein expression of CB1 receptors have been shown depending on the technical approach used or the brain region studied.
Despite the current discrepancies regarding cannabinoid receptors changes in depression and schizophrenia, present findings point to the endocannabinoid system as a pivotal neuromodulatory pathway relevant in the pathophysiology of mental disorders.