Cannabis use and cognitive functioning in first-episode schizophrenia patients

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Abstract

Cannabis is one of the most widely used illicit drugs in the world. In healthy individuals cannabis is associated with cognitive impairments. Research into the effect of cannabis use in schizophrenia has yielded contradictory findings. Our aim has been to explore the correlates of cannabis use in cognitive and psychopathological features, both cross-sectional and longitudinally, in early phases of schizophrenia.

104 patients with a first episode of non-affective psychosis and 37 healthy controls were studied. Patients were classified according to their use of cannabis prior to the onset of the illness (47 users vs. 57 non-users). They were cross-sectionally and longitudinally studied and compared on clinical and cognitive variables and also on their level of premorbid adjustment.

Cannabis user patients had better attention and executive functions than non-cannabis user patients at baseline and after 1 year of treatment. Both groups showed similar improvement in their cognitive functioning during the 1-year follow-up period. We also found that users had a better social premorbid adjustment, particularly during the early periods of life. The amount of cannabis consumed and the length of time of consumption did not significantly relate to cognitive performance.

The use of cannabis does not seem to be associated with a negative effect on cognition in a representative sample of first-episode schizophrenia patients. Cannabis user patients appear to comprise a subgroup of patients with a better premorbid adjustment and premorbid frontal cognitive functions.

Introduction

Cannabis is currently one of the most used illicit drugs worldwide (Wadsworth et al., 2006, Cohen et al., 2008). Studies in healthy individuals have established that acute (Solowij, 1998) and chronic (Wadsworth et al., 2006) consumption of cannabis is associated with cognitive impairments (Pope et al., 2001, Solowij, 1995, Pope and Yurgelun-Todd, 1996, Pope et al., 2003, Solowij et al., 2002) and to transient schizophrenia-like positive, negative, and cognitive symptoms (D´Souza et al., 2009).

In schizophrenia, cognitive dysfunction is a core feature already present at early stages, which should be considered as a potential endophenotype (Gonzalez-Blanch et al., 2007), still present long after treatment initiation (D'Souza et al., 2005). The relationship of cannabis consumption with these cognitive dysfunctions in schizophrenia is still obscure and research has brought forth contradictory findings. The use of cannabis has been related to memory impairments (D'Souza et al., 2005), to a better cognitive performance (Joyal et al., 2003, Jockers-Scherubl et al., 2007), and to a long term sparing of cognitive functions (Stirling et al., 2005) and absence of associations has also been reported (Carey et al., 2003, Pencer and Addington, 2003).

As regards clinical features, cannabis use has been associated with more severe positive symptoms (Caspari, 1999, Degenhardt et al., 2007, Grech et al., 2005) and earlier onset of the psychosis (Barnes et al., 2006, Gonzalez-Pinto et al., 2008).

On the other hand, negative symptoms and difficulties in social skills have been proposed as risk factors for cannabis abuse (Mueser et al., 1998) and cannabis users have shown poorer clinical and social outcomes (Blanchard et al., 2000, Kavanagh et al., 2002). Consequently, it has been suggested that some patients would rely on cannabis consumption to alleviate their symptoms (D'Souza et al., 2005). Contrarily, cannabis user patients have also been described as having a lesser severity of negative symptoms and better social skills (Arndt et al., 1992, Kirkpatrick et al., 1996) and premorbid adjustment (Arndt et al., 1992, Sevy et al., 2001). Accordingly, Joyal et al. (2003) suggested that cannabis user patients with schizophrenia might comprise a differentiated subgroup of subjects characterized by more positive and less negative symptoms and who would also have better cognitive functioning and the social skills necessary to engage in behaviours related to drug consumption.

The aim of the current article was to explore cognitive and psychopathological features, both cross-sectionally and longitudinally, of those first-episode schizophrenia patients that report using cannabis, as opposed to those that do not use this substance. We hypothesized that patients that report using cannabis would show a better cognition and premorbid adjustment and therefore would have to be considered as a specific subgroup of patients.

Section snippets

Study setting and financial support

The data for these analyses were taken from patients of a large epidemiological and longitudinal intervention program of first-episode psychosis (PAFIP), carried out at the University Hospital Marques de Valdecilla, Cantabria, Spain. A detailed description of the PAFIP methodology is available in earlier publications (Crespo-Facorro et al., 2007, Pelayo-Teran et al., 2008).

Briefly, the study was conducted at the outpatient clinic and the inpatient unit at the University Hospital Marques de

Results

Sociodemographic data for patients who consumed (users) and those who did not consume (non-users) are presented in Table 1. Cannabis user patients were younger, had fewer years of education, and a lower premorbid IQ. They had also an earlier age of illness onset than did non-users. Males were also significantly more represented in the group of cannabis users.

The patients who used cannabis and other substances (N = 21) were compared with patients who only consumed cannabis (N = 26). The two groups

Discussion

Our research has shown that cannabis user schizophrenia patients have better attention and executive functions than non-user patients at baseline and after 1 year of treatment. Overall, both groups of patients showed a similar increase in their performance on cognitive tasks during the 1-year follow-up period. We also found that cannabis users had a better social premorbid adjustment, particularly during the early periods of life. The amount of cannabis consumed and the length of time of

Role of funding source

The present study was performed under the following grant support: Instituto de Salud Carlos III PI020499, PI050427, and PI060507, Plan Nacional de Drogas Research Grant 2005-Orden sco/3246/2004, SENY Fundació Research Grant CI 2005-0308007 and Fundación Marqués de Valdecilla API07/011. These institutions had no other role in the study design, the data collection, data analysis, interpretation of the data, writing or decision to submit the paper.

Contributors

All authors have contributed significantly to the current paper. All authors have approved to submit the paper.

Conflict of interest

Prof. Vazquez-Barquero and Prof. Crespo-Facorro have received unrestricted research funding from AstraZeneca, Pfizer, Bristol-Myers Squibb, and Johnson & Johnson, which has been deposited into research accounts at the University of Cantabria.

Prof. Vazquez-Barquero has received honoraria for his participation as a speaker at educational events from Johnson & Johnson.

Prof. Crespo-Facorro has received honoraria for his participation as a speaker at educational events from Pfizer, Bristol-Myers

Acknowledgements

The present study was performed at the Hospital Marqués de Valdecilla, University of Cantabria, Santander, Spain, under the following grant support: Instituto de Salud Carlos III PI020499, PI050427, and PI060507, Plan Nacional de Drogas Research Grant 2005-Orden sco/3246/2004, SENY Fundació Research Grant CI 2005-0308007 and Fundación Marqués de Valdecilla API07/011.

No pharmaceutical company supplied any financial support towards it. The study, designed and directed by B C-F and JL V-B,

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