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Daily Consumption Of Cannabis Predisposes To Appearance Of Psychosis And Schizophrenia, Study Finds

March 26, 2009
University of Granada
A study carried out in Spain has analyzed the characteristics of the psychosis provoked by the continuous consumption of cannabis. The research was carried out with a sample of 92 patients with episodes of psychosis, and confirmed that, in those patients with a normal neuronal development who suffered psychotic episodes, 66 percent were cannabis users.

The daily consumption of cannabis predisposes to the appearance of psychosis and schizophrenia, and those episodes of psychosis which are fruit of this substance present certain specific characteristics, both before their appearance and in the clinical presentation of the psychosis.

This is one of the conclusions of the doctoral thesis "Neurodevelopment and environmental stress in initial psychosis: transversal analysis of the ESPIGAS study", carried out by researcher Miguel Ruiz Veguilla, of the Institute of Neurosciences of the University of Granada (Spain) and supervised by professors Manuel Gurpegui Fernández de Legaria and Jorge Cervilla Ballesteros. Ruiz Veguilla is also the person in charge fo the Unit of Development Neuropsychiatry of Jaén (Spain).

This work has studied the risk factors associated with schizophrenia, identifying and characterizing in depth those psychosis associated with a continual consumption of cannabis. They carried out a study with 92 subjects, 50 of which had developed a psychosis without presenting signs of an "abnormal neurodevelopment", this is, they had been doing well academically, they had a group of friends (no social isolation) and they presented a good motor coordination. In addition, these subjects did not show a family history of episodes of psychosis in first or second degree.

Identifying a new type of psychosis

The research work carried out by Miguel Ruiz Veguilla has identified a connection between cannabis consumption and psychosis in subjects with a good premorbid performance, and without signs of minor neurological alterations, which in his opinion might point out "a psychopathological way associated with psychosis in subjects with less predisposition".

Thus, 66% of the patients with psychosis who participated in the study and had a normal neurodevelopment admitted to have consumed cannabis daily or almost every day, whereas 43% of the participants with markers of an abnormal neurodevelopment (those already indicated: bad previous social and academic behaviour, a family history and a "clumsier" attitude when they carry out tasks of motor coordination and complex motor acts) were drug users too.

In the light of the results of his doctoral thesis, the researcher of the University of Granada says that, after having identified a type of psychosis where the environmental factor plays a more relevant role, we should now answer the question of which is the prognosis, in the long term, of those subjects with a good previous behaviour, whose psychosis is associated with a high consumption of cannabis.

The results of this research work have been published in the journals Schizophrenia Research and European Psychiatry.

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Materials provided by University of Granada. Note: Content may be edited for style and length.

Journal References:

  1. Miguel Ruiz-Veguilla, Manuel Gurpegui, María Luisa Barrigón, Maite Ferrín, Esther Marín, José Luis Rubio, Blanca Gutiérrez, Antonio Pintor, Jorge Cervilla. Fewer neurological soft signs among first episode psychosis patients with heavy cannabis use. Schizophrenia Research, 2009; 107 (2-3): 158 DOI: 10.1016/j.schres.2008.08.001
  2. M. Barrigón, M. Ruiz-Veguilla, M. Anguita, F.J. Díaz, J. Cervilla, M. Gurpegui. Temporal relationship of cannabis and other illegal drug use with the onset of first-episode non-affective psychosis. Schizophrenia Research, 2008; 9866 DOI: 10.1016/j.schres.2007.12.146
  3. Miguel Ruiz-Veguilla, Jorge A. Cervilla, Maria Luisa Barrigón, Maite Ferrín, Blanca Gutiérrez, Estibaliz Gordo, Manuel Anguita, Antía Brañas, Jesús Fernández-Logroño, Manuel Gurpegui. Neurodevelopmental markers in different psychopathological dimensions of first episode psychosis: The ESPIGAS Study. European Psychiatry, 2008; 23 (8): 533 DOI: 10.1016/j.eurpsy.2008.04.003

Cite This Page:

University of Granada. "Daily Consumption Of Cannabis Predisposes To Appearance Of Psychosis And Schizophrenia, Study Finds." ScienceDaily. ScienceDaily, 26 March 2009. <>.
University of Granada. (2009, March 26). Daily Consumption Of Cannabis Predisposes To Appearance Of Psychosis And Schizophrenia, Study Finds. ScienceDaily. Retrieved December 4, 2023 from
University of Granada. "Daily Consumption Of Cannabis Predisposes To Appearance Of Psychosis And Schizophrenia, Study Finds." ScienceDaily. (accessed December 4, 2023).

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