Effects of Chronic Intake of Cannabis on Contrast Sensitivity

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.

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Key information

Conditions

Cannabis Dependence Chemically-Induced Disorders Marijuana Abuse Mental Disorders Substance-Related Disorders

Age range

18 year–50 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Strasbourg, Bas-Rhin, 67300, France

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Electroretinogram

Other

contrast sensitivity tests

Other

Primary outcomes

The contrast detection treshold

Time frame: up to 9 days after inclusion

Comparison of the contrast detection threshold of the 3 groups

Sponsors and collaborators

Lead sponsor

University Hospital, Strasbourg, France

Other

Registry information

Important dates

Study start: 2013
Primary completion: 2015
Study completion: 2018
First posted: Feb 18, 2013
Registry last updated: Jun 8, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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