Examine the Feasibility of a Standardized Field Test for Marijuana and Alcohol Impairment: Laboratory Evaluations

Alcohol and Cannabis (CNB) are two of the most widely used intoxicants. The effects of driving while intoxicated on alcohol are well documented, resulting in numerous drunken driving laws and regulations. As CNB begins to be decriminalized, medical CNB use allowed in multiple U.S. states, and perception of harmfulness falls, CNB use is predicted to rise and it will become increasingly common to publicly encounter persons who recently used the drug. An area of potentially high concern is if ever-greater numbers of CNB users and its legalization will increase the risk of driving while intoxicated from recent CNB use, thereby increasing the risks to public safety. This study aims to examine the combined effects of smoking marijuana and drinking alcohol on simulated driving.

Alcohol is one of the most widely used substances. The effects of driving while intoxicated are well documented, leading to laws and regulations behind drunk driving. Marijuana is also a commonly abused drug. Marijuana use is not specific to social class, is linked to cognitive impairment and may be the cause of intoxication-induced accidents. The effects of marijuana intoxication on driving impairments are less documented. Data is being gathered in regards to this risk from our Neuroscience of Marijuana Impaired Driving study. The principle investigator's previous research includes the Brain and Alcohol Research with College Students (BARCS) study along with additional epidemiological studies reveal that most marijuana smokers also consume alcohol when they are intoxicated. These drugs interact pharmacodynamically and change each other's levels in the user's blood. They both have deleterious effects on driving. These effects are not additive but rather multiplicative. Someone using both substances will show more deleterious effects than someone using just one of these substances. This study will aim to investigate the brain and behavior in the same individuals, using a similar design to the NHTSA: Examine the Feasibility of a Standardized Field Test for Marijuana Impairment study. This structure coupled with past alcohol driving studies (Marijauna and Alcohol Impaired Driving) uses similar techniques of other measures of drunk driving. We hypothesize that alcohol and marijuana use combined will lead to greater impairment in a simulated driving task, as well as other driving related cognitive impairments. This study will aim to study feasible roadside sobriety tests for marijuana impairment.

The study will consist of 5 days (screening visit and 4 dose visit days). In a randomized, counterbalanced, double-blind study, investigators will dose participants with alcohol to a legal amount of 0.05% blood alcohol content on 3 study days and dose to 0.08% blood alcohol content on 1 study day. Then investigators will administer high THC marijuana, low THC marijuana or placebo marijuana using paced inhalation through a vaporizer. Participants will include 12 regular alcohol consumers aged 21 to 40 years of age; all participants must report smoking and drinking together. Following this dosing, investigators will assess impairment through cognitive testing as well as a simulated driving test and neuropsychological tests. Samples of blood will also be collected at multiple time points throughout the study visits to be measured for THC concentration and its metabolites. This allows clarification between the relationship of impairment, as well as subjective and objective intoxication, and levels of THC and it's metabolites in the users system.

Eligibility Criteria:
Inclusion Criteria:

* Must have a driver's license; recent 2 years highway driving experience
* Cannabis use for at least the past 2 years and report of getting high when smoking cannabis to avoid recruiting novice/inexperienced users.
* Reports regularly drinking and smoking (does not need to be at the same time)
* Use cannabis at least 5 times within life up to daily use, with occasional day of abstinence with no symptoms of craving or withdrawal.

Exclusion Criteria:

* Pregnancy, breastfeeding, and ineffective birth control methods.
* Current severe substance use disorder (except cannabis and tobacco substance use disorders)
* history of adverse effects with cannabis use
* serious medical, neuro-ophthalmological, or neurological illness (i.e. cancer, seizure disorders, encephalopathy)
* current diagnosis of any DSM-5 psychiatric disorder
* prior diagnosis of any DSM-5 psychiatric disorder
* report of any psychotic disorder in a first-degree relative
* history of head trauma with loss of consciousness \> 30 minutes or concussion lasting 30 days.
* any medical/neurological condition that could compromise neurocognitive performance (i.e. epilepsy, multiple sclerosis, fetal alcohol syndrome)
* recovering alcoholics or anyone currently abstaining from alcohol.