Electrophysiological Study of the Functioning of Magnocellular Visual Pathway in Regular Cannabis Users

This study will evaluate the impact of regular use of cannabis on the spatial sensitivity of magnocellular system (visual event-related potential, visual ERP).

Secondary purposes of this study are to evaluate the impact of regular use of cannabis on the temporal sensitivity of magnocellular system (visual event-related potential), on the dynamics of cortical visual processing during face perception test (visual event-related potential) and on functioning of retinal photopic and scotopic systems (electroretinogram).

The ancillary study is a genetic analysis of a group of candidate genes that aims to identify biomarkers for changes in visual processing. This will allow to distinguish among more homogeneous and specific groups in future studies on larger cannabis user population. This ancillary study concerns all participants subject to their informed consent (facultative study).


Eligibility Criteria:
Inclusion Criteria:

* Affiliation to social security plan
* Normal visual acuity or adjusted to normal and normal dilated fundus examination
* Signature of informed consent
* Cannabis user group: More than 7 cannabis uses per week during the previous month
* Cannabis user group: Positive urinary analysis for presence of cannabis
* Healthy, non user control group: Absence of cannabis and tobacco use during last 12 months
* Healthy, non user control group: Negative urinary analysis for presence of cannabis
* Healthy, non user control group: Age and sex matching with cannabis user group
* Healthy, tobacco user control group: Tobacco use from at least 12 months
* Healthy, tobacco user control group: Low to very strong addiction to tobacco (Fagerström test)
* Healthy, tobacco user control group: Absence of cannabis use from more than 12 months
* Healthy, tobacco user control group: Negative urinary analysis for presence of cannabis
* Healthy, tobacco user control group:Age and sex matching with cannabis user group
* Schizophrenia patient control group: Schizophrenia according to DMS IV criteria (MINI test)
* Schizophrenia patient control group: Absence of cannabis use from more than one month (regardless of tobacco use)
* Schizophrenia patient control group: Negative urinary analysis for presence of cannabis
* Schizophrenia patient control group: Age and sex matching with cannabis user group

Exclusion Criteria:

* Acute psychiatric pathology (axis I of DSM IV, measured by MINI) except anxiety disorder (except schizophrenia group)
* Deficiency of the subject making difficult or impossible his/her participation to the study or the comprehension of the information
* Dyslexia
* Addiction to alcohol according to AUDIT scale
* Abuse or addiction to other substances according to DSM IV criteria
* Acute retinal disorder
* Chronic glaucoma
* Ophthalmic pathology affecting visual acuity
* Current ocular infection
* Persons under guardianship, curatorship or judicial protection
* Pregnant or breast-feeding women
* Persons with life-and-death emergency
* Absence of social security plan
* Results of preliminary medical examinations incompatible with the study
* Simultaneous participation to another therapeutic interventional study