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Psychotic disorders hospitalizations associated with cannabis abuse or dependence: A nationwide big data analysis


First published: 05 December 2019

We aimed to describe and correlate the hospital panorama of psychotic disorders (PD) with cannabis use (CU) trends in all Portuguese public hospitals.



We conducted a retrospective observational study that analysed all hospitalizations that occurred in Portuguese public hospitals from 2000 to 2015. Hospitalizations with a primary diagnosis of PD or schizophrenia were selected based on Clinical Classification Software diagnostic single‐level 659. Episodes associated with CU were identified by the International Classification of Diseases Version 9, Clinical Modification code 304.3/305.2 that correspond to cannabis dependence/cannabis abuse.



The number of hospitalizations with a primary diagnosis of PD and schizophrenia associated with CU rose 29.4 times during the study period, from 20 to 588 hospitalizations yearly (2000 and 2015, respectively) with a total of 3,233 hospitalizations and an average episode cost of €3,500. Male patients represented 89.8% of all episodes, and the mean/median age at discharge were 30.66/29.00 years, respectively. From all hospitalizations with a primary diagnosis of PD or schizophrenia, the ones with a secondary diagnosis of CU rose from 0.87% in 2000 to 10.60% in 2015.



The increase on secondary diagnosis coding and the change on cannabis patterns of consumption in Portuguese population with an increasing frequency of moderate/high dosage cannabis consumers may explain the rise on PD hospitalizations.



Cannabis is one of the most commonly used recreational drugs and is also utilized for its medical properties (Carliner, Brown, Sarvet, & Hasin, 2017; Davis, 2016). The primary psychoactive compound of cannabis is delta 9‐tetrahydrocannabinol that activates cannabinoid receptors. These receptors when activated will interfere in brain activity, more specifically in areas of the brain that are responsible for cognition, perception, anxiety, fear, memory and reward (Grotenhermen, 2003).

Most studies analysing cannabis use (CU) impact on psychotic disorders (PD) identify two possibilities of relation: (a) first, CU as a contributing cause to initiate a PD and, (b) second, a shared vulnerability between CU and the beginning of a PD, where the risk factors for the development of a PD may also play a role in the presence of addictive behaviours (Ksir & Hart, 2016).

PD are one of the most serious group of medical conditions that may appear after CU and may generate comorbidities in an acute or chronic timeline (Gage, Hickman, & Zammit, 2016). Although it is difficult to establish a direct causal link between CU and PD, a large number of observational studies have found a clear association between CU and schizophrenia and the development of psychotic symptoms (Colizzi et al., 2018; Ferdinand et al., 2005; Hall & Degenhardt, 2000; Miettunen et al., 2008; Ortiz‐Medina et al., 2018; Regier et al., 1990; Semple, McIntosh, & Lawrie, 2005). Patients diagnosed with a first episode of psychosis or with schizophrenia are more likely to report current or prior use of cannabis, compared with the general population. Cannabis properties also play a role with the incidence of a first psychotic event being linked to the dosage of the cannabis used by the patient (Andreasson, Allebeck, Engstrom, & Rydberg, 1987; Di Forti et al., 2019; Roncero et al., 2018; Zammit, Allebeck, Andreasson, Lundberg, & Lewis, 2002). Continued CU not only might play a role on the first psychotic event but also affects negatively the prognosis of a patient after the first episode of psychosis, increasing the relapse rate (Schoeler et al., 2016). According to Tennant et al., PD related with CU may occur in three distinct situations: (a) auto‐limited psychosis caused by acute cannabis consumption that ends after stopping the consumption, (b) psychosis that develops during CU that requires medical treatment or hospitalization even after stopping the consumption, and (c) psychosis that manifests years after CU but is likely directly related to it (Rylander, Winston, Medlin, Hull, & Nussbaum, 2018; Tennant, 2005).

CU is linked to an increase in hospital visits and in the utilization rates of emergency and hospital services for psychosis (Rylander et al., 2018). In France, emergency department visits associated with CU have increased, and in the United States, there was a significant increase on CU‐related hospitalizations in the recent years (Charilaou et al., 2017; Noel, Maghoo, Franke, Viudes, & Minodier, 2019). In times where many countries are considering the legalization of cannabis for recreative consumption, research regarding cannabis role in PD arises as an important tool to understand its true impact in terms of public and mental health. In Portugal, the proprietorship and consumption of cannabis was decriminalized in 2001 together with all other drugs and is only considered a crime if a single individual possesses more than 10 standard doses. The legalization of the use of cannabis for recreative consumption is currently being debated by all political parties. The estimated prevalence of CU at any period of life in the Portuguese population is 9.7%, a lower value when compared with the average European prevalence. When analysing the data on European patterns of cannabis consumption, 7.4% of the population in Europe consumed cannabis in 2018 (European Monitoring Centre for Drugs and Drug Addiction, 2019). However, regarding the moderate/high consumption of cannabis, it is estimated that Portugal has a higher prevalence of consumers when compared with the average European prevalence (2.3–3.2% vs. 1.0%; Serviço de Intervenção nos Comportamentos Aditivos e nas Dependências (SICAD), 2017).

The main goal of this study was to analyse clinical, demographic, and administrative trends regarding PD hospitalizations associated with cannabis abuse and/or dependence in the recent years in Portugal. The secondary goal of this study was to use secondary data such as administrative databases in Psychiatry and Epidemiology observational research.



We conducted a retrospective observational study using a database provided by Administração Central dos Serviços de Saúde that contained all hospitalizations registered in Portuguese public hospitals from 2000 to 2015. We selected all hospitalizations associated with CU, identified based on International Classification of Diseases Version 9, Clinical Modification codes of diagnosis 304.3 and 305.2 that correspond to cannabis dependence and cannabis abuse, respectively. These codes belong to the larger group of neurotic disorders, personality disorders, and other nonpsychotic mental disorders in International Classification of Diseases Version 9, Clinical Modification. Hospitalizations with a primary diagnosis of schizophrenia and other PD defined by the Clinical Classification Software diagnostic single‐level 659 were selected, representing a broad group of diagnosis that gather all psychotic conditions (Appendix A).

Information regarding birth date, sex, primary and secondary diagnoses, admission date, discharge date, length of stay (LoS), discharge status, and hospital charges from each single hospitalization episode were gathered. Hospital charges were calculated from expenditure tables for the Portuguese National Health Service hospital reimbursements, as defined by governmental decree in 2009 (in Diário da República) and were estimated by using a diagnosis‐related groups‐based budget allocation model.

Descriptive statistical analyses, independent sample t tests, and linear regression models with 95% confidence intervals (CI) were performed to assess temporal trends in the number of admissions, age at admission, and LoS between 2000 and 2015, using IBM SPSS Statistics v.24 for Windows (Armonk, NY: IBM Corp).



A total of 3,233 hospitalizations with a primary diagnosis of PD or schizophrenia and with a secondary diagnosis of cannabis abuse or dependence occurred in all Portuguese public hospitals between the year 2000 and 2015. A steady increase on the number of hospitalizations occurred throughout the study period (R = 0.928; B = 35.649 95% CI [27.416, 43.881]), from 20 hospitalizations in 2000 to 588 in 2015 a 29.4 times increase (Table 1). Most of the hospitalizations were associated with male patients, representing 89.8% of all admissions and a total of 2,902 hospitalizations, a higher frequency when compared with all PD hospitalizations (62.7%; n = 42,998). The mean and median age at the time of discharge were 30.66 and 29.00 years of age, respectively, with a minimum range of 14 and maximum of 100 years. The age at discharge increased during the study period (R = 0.154; B = 0.399, 95% CI [0.310, 0.487]). Approximately 3.3% (n = 107) of the hospitalizations occurred in patients younger or with 18 years old, and the mode was 25 years with a total of 173 hospitalizations. The mean age was similar for male and female patients (males: 30.63; females: 30.69, p = .540). When considering all PD hospitalizations, the mean and median age were 42.00 and 44.00 years old.


Manuel Gonçalves‐PinhoMiguel BragançaAlberto Freitas


Source: https://doi.org/10.1002/mpr.1813   First published: 05 Dec. 2019