Effects of Chronic Intake of Cannabis on Contrast Sensitivity

Study Overview
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Brief Summary
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Rates of driving under the influence of cannabis have risen in recent years. Cannabis is involved in 1/3 of motor vehicle collisions. The chronic use of cannabis is known to affect dopaminergic regulation and may thus impair contrast sensitivity. In turn, contrast sensitivity disorders could originate difficulties to anticipate and avoid collision with objects, especially when objects are in movement. The investigators goal is to examine the effects of a chronic intake of cannabis on contrast sensitivity. The observed values will be compared to standard references. In addition, since smoking cannabis is always associated with tobacco, the investigators will control the effects of tobacco on contrast sensitivity. In this study, the investigators will include 36 cannabis addicts, 36 tobacco addicts and 36 no smokers. The investigators will present gratings with different spatial frequencies and the investigators will determine contrast thresholds for static and dynamic (moving) gratings. The investigators predict that cannabis addicts will present abnormal contrast sensitivity especially in case of dynamic presentation of gradings.

Official Title
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Effects of Chronic Intake of Cannabis on Contrast Sensitivity

Conditions
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Cannabis Dependence

Intervention / Treatment
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* Other: electroretinogram
* Other: contrast sensitivity tests


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Cannabis Arm patient addicted to cannabis Positive CAST test result Urine tested positive for cannabis metabolites Tobacco Arm positive Fagerström test result No cannabis intake in the last year before inclusion No previous history of cannabis use Healthy Volunteers No tobacco or cannabis intake in the last year before inclusion No history of addictive disorders Exclusion Criteria: addiction to other substances than cannabis or tobacco benzodiazepine treatment patient with history of benzodiazepine treatment patient with history of general anesthesia in the last 3 months before inclusion patient with history of head trauma Pregnant woman breast feeding woman Adults under supervision or guardianship

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Other
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Cannabis Arm<br>patient addicted to cannabis | Other: electroretinogram<br> <br> Other: contrast sensitivity tests<br> <br> |
| Other: Tobacco Arm<br>patient addicted to tobacco | Other: electroretinogram<br> <br> Other: contrast sensitivity tests<br> <br> |
| Other: Healthy volunteers<br>no smokers | Other: electroretinogram<br> <br> Other: contrast sensitivity tests<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The contrast detection treshold | Comparison of the contrast detection threshold of the 3 groups | up to 9 days after inclusion |