A Phase 1 interventional study of THC 20mg and Placebo in Cannabis Use, sponsored by Washington State University. Recruiting at 1 site in United States. Open to participants aged 21 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-10-29.
Sponsored by Washington State University · Phase 1, Interventional, and Basic science
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This study will examine how a moderate dose of THC affects mood and cognitive functioning in regular cannabis users. The study uses a double-blind, placebo-controlled, crossover design, meaning each participant will complete two sessions. Specifically, each participant will be given active cannabis (20 mg THC) in one session, and placebo in the other session. The order will be randomized across participants, so half will receive cannabis first, and the other half will receive placebo first.
Ninety two adults who use cannabis at least weekly will be recruited from the local community. After an online screening survey, eligible participants will attend a laboratory visit where the participants will provide informed consent and complete saliva and urine drug tests to confirm recent abstinence from cannabis and absence of other drugs. Participants who pass screening will complete baseline questionnaires of cannabis use patterns, depression, anxiety, ADHD symptoms, emotion regulation, affect, and demographic information.
Cannabis and placebo materials (obtained from NIDA) will be vaporized using a Volcano vaporizer device. Participants will inhale the vapor under supervision of one of the PIs. Neither the participant nor the researcher assessing outcomes will know which product is administered. After vaping, participants will complete repeated affect ratings and a battery of cognitive tests assessing executive functions like planning, inhibition, working memory, and cognitive flexibility. The participants will then watch a nature video and report their affect.
At the end of each session, participants will remain in a supervised room with entertainment and snacks until at least four hours have passed since vaping and the participants report feeling sober. Their food consumption will be monitored and recorded.
The participants will then return for a second session with the opposite study condition (THC or placebo) one week later. Both sessions follow the same procedures. Participants are fully debriefed after completing the study.
Design: The investigators will address the research questions using a double-blind, placebo-controlled, crossover design.
Cannabis Procurement, Storage, and Transport: Cannabis will be obtained from the National Institute on Drug Abuse (NIDA). The investigators will obtain cannabis containing 13.7% THC (barrel #1592). Our plan for dosing considers potency (grams of flower x 1000 x %THC = mg THC), so participants in the 20 mg THC condition will be administered .15g of 13.7% THC cannabis flower. The placebo will also be obtained from NIDA.
Cannabis will be stored in the PI's secure cannabis storage facilities in the Veterinary and Biomedical Research (VBRB) building. A maximum of 24 hours before a scheduled testing session, an individual authorized by the DEA will transport a small amount of cannabis or placebo (corresponding to 20 mg THC) from the secure VBRB storage facilities to the psychology building, where participants will vape the cannabis. The product will be stored in the chamber of a Volcano Vaporizer in a locked room.
Recruitment: A total of 92 cannabis users will be recruited from Pullman and the neighboring communities. Advertisements will be placed in local cannabis dispensaries and on social media (e.g., Facebook Free \& For Sale, Reddit, Instagram). The investigators will also email chronic cannabis users who have participated in our former cannabis studies (and have indicated willingness to be contacted with invitations for subsequent studies) to invite them to participate. These advertisements and emails will include a link to an online Qualtrics survey used to determine eligibility. This survey will be used to screen for serious psychiatric conditions (psychosis, bipolar I, panic disorder), a family history of psychosis, neurological disorders, chronic medical conditions (e.g., heart disease, diabetes), learning disabilities, intellectual disabilities, history of multiple concussions or head injury that may impact cognition, pregnancy or lactation, and history of adverse experiences with cannabis (psychosis, panic attacks), use of illicit drugs in the past 6 months, heavy alcohol use (>4 drinks, >4 times/week), and smoking/nicotine use. Eligible participants will need to have used cannabis at least once a week for at least one year, the participants will need to indicate that they typically inhale cannabis, and be willing to abstain from using any cannabis on the day of their scheduled testing session (minimum of 8 hours of abstinence). This survey will be used to obtain contact information from interested and eligible candidates. Ineligible participants will not be given the opportunity to enter their contact information, so sensitive information will only be collected from anonymous individuals. Eligible candidates will be contacted using the contact information provided, and the testing session will be scheduled. Participants will be instructed not to use any cannabis on the day of the testing session (from midnight onward).
Consent \& Drug Screen: Participants will meet the research assistant in The Health \& Cognition (THC) lab in the Department of Psychology at WSU. After obtaining written informed consent, participants will be asked when they last ate and drank (anything but water) and when they last used cannabis. Participants who report using cannabis that day will be rescheduled and will be reminded that they must abstain from any cannabis use on the day of the testing session. To further verify abstinence from cannabis on the day of the testing session, the participants will be asked to complete a THC saliva test. The participants will then be asked to complete a 12-panel urine drug test to ensure the participants test negative for illicit drugs. Participants who test positive for illicit drugs are not eligible and will not be permitted to complete the study.
Survey and Baseline Assessments: Participants who pass the drug test (test negative for illicit drugs), will be asked to put on a Muse S Athena EEG headband with assistance from the research assistant (RA). The participants will then rate how high they feel using a scale from 0 = "not high at all" to 10 = "extremely high." Next, the participants will complete standardized, valid, and reliable measures of their cannabis consumption patterns (Daily Sessions, Frequency, Age of Onset, and Quantity of Cannabis Use Inventory), motives for use (Marijuana Motives Questionnaire [MMQ]), depression (Center for Epidemiologic Studies Depression Scale [CES-D]), anxiety (Beck Anxiety Inventory [BAI]), ADHD symptoms (Barkley Adult ADHD Rating Scale - IV), emotion regulation (Difficulties in Emotion Regulation Scale [DERS]), affect (Daniels Five-Factor Measure of Affective Well-Being [D-FAW]), and demographic information. The information from this survey will be used to characterize the sample, determine covariates that should be controlled for in analyses, and examine the potential moderating effects of depression/anxiety/emotion regulation on cannabis induced changes in cognition and affect.
Drug Administration: Once the baseline assessments have been obtained, the researcher will bring the participant to the vaping room for their vaping session. This is a secluded room (none of the neighboring rooms are currently in use by people) in the basement of the building with a functioning fume hood. The researcher will position the Volcano Vaporizer pre-loaded with cannabis containing 20 mg of THC or placebo (the researcher and participant will be blind to the product) near the participant. The researcher will turn the vaporizer on and will wait until it heats up to 210 degrees Celsius. This temperature is ideal as it is not hot enough for the plant material to burn, so many of the toxins associated with smoking are not released. The researcher will set up a Zoom videoconferencing session on an iPad/computer and will text one of the principal investigators (PIs) to join the Zoom call. Importantly, this Zoom session will NOT be recorded. The RA will then go to an adjacent room and wait until the cannabis session is complete to aid with their blinding to the drug condition. Once one of the PIs joins the Zoom call, the investigators will instruct the participant to begin inhaling the vapor and exhaling into a "sploofy" carbon filter. The participants will be asked to try to inhale for a minimum of 2 seconds, and hold for 2 seconds, before exhaling into the sploofy. The PI will count the total number of puffs the participant inhales and will time the duration of their inhalations and holds. Once the participant has inhaled 30 puffs, they will be asked to exhale into the air and to look to see if there is any visible vapor. If the participants see visible vapor, they will continue to take more puffs and exhale into the sploofy. Every 5-10 puffs, the participants will exhale into the air to see if they notice any vapor. This will continue until the participants don't see any vapor. The PI will text the RA when the vaping session is complete, and the RA will return, clean the mouthpiece with rubbing alcohol, put the Volcano Vaporizer away, and turn on the fume hood. The RA will then bring the participant back to the original lab room to complete the cognitive tests.
Subjective States: Participants will be given a short survey on an iPad asking them to rate how high they feel using a scale from 0 = "not high at all" to 10 = "extremely high." The participants will also rate the level of good drug effects they are experiencing and their liking of those drug effects using similar 0 to 10 scales. Participants will be asked to rate their affect using the D-FAW.
Cognitive Tests: Participants will be asked to complete cognitive tests of planning, inhibition, task switching/cognitive flexibility, and working memory, including tests of prospective memory, the N-back, digit span backwards, tower test, zoo maps test, Stroop test, Go/No-Go test, an intra- and extra-dimenstional set shifting task (IDED), and verbal fluency category switching tests.
Nature Video and AWE: Participants will then be brought to an adjacent room where they will watch a brief nature video (there are two versions of this video that will be counterbalanced). After the nature video, the participants will provide ratings of awe, their feelings of connectedness to nature, and their affect using the D-FAW. Finally, participants will be asked to rate the strength of their subjective high, good drug effects, and liking of the drug effects on an iPad. The EEG headband will then be removed.
Sobering and Debriefing: Participants will then sit and play video games and/or watch TV or read until it has been a total of 4 hours since their vape session ended, and the participants report feeling completely sober. The room is equipped with couches, chairs, a TV with streaming platforms, and a video game system. Snacks (e.g., fruit snacks, granola bars, hot pockets, uncrustables, chips, chocolate bars, nuts, jerky, soda, juice, chocolate milk, water) will also be available for participants to consume while they wait. This room is equipped with a two-way mirror, and an RA will monitor participants via the window in the adjacent room to ensure the participants do not attempt to leave the lab and to monitor and record the snacks/beverages participants choose to consume (the calories, fat, protein, and carbohydrate contents of each) and the activities the participants choose to engage in while they sober up. Participants will be informed that the RA is in the adjoining room, monitoring them, and that the participants can call them for assistance at any time. The RA will enter the room every 30 minutes to collect intoxication ratings. Participants will also be asked to rate how much they enjoyed each food product or beverage they consumed in the prior 30 minutes using a 0 (dislike very much) to 10 (like very much) rating scale. Participants will be permitted to leave the lab after it has been a total of 4 hours have passed since their vape session ended, and they report feeling sober (give a 0 on the intoxication rating scale).
Participants will then return for their second session, which will be identical to the first, except those administered 20 mg of THC in session 1 will be administered placebo in session 2, and those administered placebo in session 2 will be administered 20 mg of THC in session 2. Participants will be debriefed and compensated at the end of session 2.
Washington State University is the lead sponsor of 83 studies on the registry; 16 are open to participants now.
Of its 7 completed or terminated interventional studies of FDA-regulated products, 4 (57%) have results posted.
Counted across the registry records on this site, refreshed daily.
The criteria were revised on the registry on Oct 29, 2026. See what changed
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Exclusion Criteria:
Participants will inhale vapor from .17 grams of cannabis containing 11.86% THC (20mg THC total) during the first session. They will inhale vapor from a placebo product during the second session.
Drug: THC 20mg · Drug: Placebo
Participants will inhale vapor from a placebo product during the first session. They will inhale vapor from .17 grams of cannabis containing 11.86% THC (20mg THC total) during the second session.
Drug: THC 20mg · Drug: Placebo
20 mg THC delivered by vaporizing 0.17 g of 11.86% THC cannabis flower obtained from NIDA, using a Volcano vaporizer.
Placebo obtained from NIDA and vaporized using a Volcano vaporizer.
Event-Based Prospective Memory - Number of Difficulty Ratings Provided
Event-based prospective memory will be assessed using a difficulty ratings task. At the beginning of the session, participants will be asked to try to remember to rate how difficult they found each test immediately after it is completed, using a 0 (not at all difficult) to 10 (extremely difficult) scale. The primary outcome of interest is the number (or percentage) of difficulty ratings they remember to provide.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Time-Based Prospective Memory - Token Task
Time-based prospective memory will be assessed using a token task. Participants will be instructed to try to remember to request a token every 10 minutes. A clock will be positioned face down on the table for them to refer to the time, and we will record their clock-checking behavior. The primary outcome is the number (or percentage) of times they remember to request the token, out of the total time of the cognitive assessment session.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Working Memory Updating - N-Back Test Accuracy
Cognitive flexibility and working memory updating will be assessed using the N-back test. Participants are shown strings of letters one at a time and are instructed to indicate whenever a letter appears that matches the letter shown two trials earlier. The primary outcome of interest is the percentage of correct responses made (i.e., the number of times they correctly recognize that the current letter matches the one from two trials before, etc.).
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Verbal Working Memory - Digit Span Backwards
Verbal working memory will be assessed using the Backwards portion of the Digit Span Test. For this test, participants are read lists of digits (of increasing lengths) and are asked to recall them in reverse order. The primary outcome of interest is the total number of correct trials.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Planning - Tower Test Total Achievement Score
Planning and problem-solving abilities will be assessed using the Tower Test. Participants are asked to move disks to reach a specified end configuration in as few moves as possible. They can move only one disk at a time and cannot place a larger disk on top of a smaller disk. The primary outcome of interest is the Total Achievement Score across the tower problems, which reflects planning effectiveness.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Planning - Zoo Maps Test Total Achieved Score
Planning and strategic thinking will be assessed using the Zoo Maps Test. Participants must plan a route through a provided zoo map while adhering to specified rules and efficiency constraints. For example, they may be instructed to start at the entrance, end at the picnic area, and use the designated paths only once. The primary outcome of interest is the total achieved score, representing accuracy when generating a self-directed route under the provided constraints.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Inhibitory Control - Stroop Test Interference Score
Inhibitory control will be assessed using the Stroop test. Participants will be shown words whose letters are in a specific color (e.g., the word "blue" in red letters. They will be tasked with naming the color of the word, which may be incongruent with the word itself. The primary outcome of interest is the interference score, which reflects the difference in reaction times between the incongruent and congruent trials.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Inhibitory Control - Go/No-Go Accuracy
Inhibitory control will be assessed using a computerized Go/No-Go task. Participants will respond as quickly and accurately as possible to designated "Go" stimuli and withhold their response when designated "No-Go" stimuli are presented. The primary outcome of interest is the number of accurate trials. Greater accuracy on the task will be indicative of greater inhibitory control.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cognitive Flexibility - Intra-dimensional/Extra-dimensional Set-Shifting Task Errors
Cognitive flexibility and attentional set-shifting will be assessed using the computerized Intra-Extra Dimensional Set-Shifting (IDED) task. Participants will select between paired visual stimuli based on learned rules and use feedback to determine the correct response as the relevant stimulus features and rules change across task stages. The primary outcome will be the number of errors committed during the extra-dimensional (ED) shift stage, in which participants must shift attention from a previously relevant stimulus dimension to a previously irrelevant dimension. Higher error scores indicate poorer cognitive flexibility. Other error types will be totaled, including simple discrimination errors, compound discrimination errors, reversal errors, and intra-dimensional (ID) errors.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cognitive Flexibility - Intra-Dimesional/Extra Dimensional Set-Shifting Task Total Accuracy
Cognitive flexibility and attentional set-shifting will be assessed using the computerized Intra-Extra Dimensional Set-Shifting (IDED) task. Participants will select between paired visual stimuli based on learned rules and use feedback to determine the correct response as the relevant stimulus features and rules change across task stages. Total accuracy will be measured as a representation of total task performance.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cognitive Flexibility - Verbal Fluency, Category Switching Accuracy
Cognitive flexibility (category switching) will be assessed using the verbal fluency category switching task. Participants will be given two categories (e.g., fruits and furniture) and be asked to generate words that belong to those categories, in alternating order, within a time limit of 60 seconds. The primary outcome of interest is category switching accuracy, which is the number of correct switches between the categories.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cognitive Flexibility - Probabilistic Reversal Learning Task, Choice Accuracy
Probabilistic reversal learning will be assessed using a computerized task in which participants select between two stimuli associated with different probabilities of receiving positive feedback. Participants will learn the more advantageous choice based on probabilistic feedback and must adjust their responses when the relative probabilities of the stimuli are reversed. The primary outcome of interest will be the proportion of trials on which participants select the stimulus associated with the higher probability of positive feedback. Higher advantageous-choice accuracy indicates more effective learning from probabilistic feedback.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Post-Treatment (T1) Intoxication Rating
Participants will be asked to rate how high they feel using a scale from 0 (not high at all) to 10 (extremely high) immediately after their vaping session.
Time frame: This outcome will be assessed during both sessions immediately after their vaping session.
Post-Treatment (T1) Good Drug Effects Rating
Participants will be asked to rate the level of good drug effects they are experiencing using a scale from 0 (none) to 10 (a lot) immediately after their vaping session.
Time frame: This outcome will be assessed during both sessions immediately after their vaping session.
Post-Treatment (T1) Drug Effects Liking Rating
Participants will be asked to rate how much they like the drug effects they are experiencing using a scale from 0 (not at all) to 10 (a lot) immediately after their vaping session.
Time frame: This outcome will be assessed during both sessions immediately after their vaping session.
Post-Cogntiive Assessment (T2) Intoxication Rating
Participants will be asked to rate how high they feel using a scale from 0 (not high at all) to 10 (extremely high) immediately after the cognitive battery.
Time frame: This outcome will be assessed during both sessions immediately after the stress challenge.
Post-Cogntiive Assessment (T2) Good Drug Effects Rating
Participants will be asked to rate the level of good drug effects they are experiencing using a scale from 0 (none) to 10 (a lot) immediately after the nature video.
Time frame: This outcome will be assessed during both sessions immediately after the stress challenge.
Post-Cogntiive Assessment (T2) Drug Effects Liking Rating
Participants will be asked to rate how much they like the drug effects they are experiencing using a scale from 0 (not at all) to 10 (a lot) immediately after the nature video.
Time frame: This outcome will be assessed during both sessions immediately after the stress challenge.
Post-Nature Video (T3) Intoxication Rating
Participants will be asked to rate how high they feel using a scale from 0 (not high at all) to 10 (extremely high) immediately after the nature video.
Time frame: This outcome will be assessed during both sessions immediately after the nature video.
Post-Nature Video (T3) Good Drug Effects Rating
Participants will be asked to rate the level of good drug effects they are experiencing using a scale from 0 (none) to 10 (a lot) immediately after the nature video.
Time frame: This outcome will be assessed during both sessions immediately after the nature video.
Post-Nature Video (T3) Drug Effects Liking Rating
Participants will be asked to rate how much they like the drug effects they are experiencing using a scale from 0 (not at all) to 10 (a lot) immediately after the nature video.
Time frame: This outcome will be assessed during both sessions immediately after the nature video.
Awe Ratings
Participants will complete ratings of awe after watching a brief (\~20 minute) nature video.
Time frame: This outcome will be assessed during both sessions, within two hours post-treatment.
Connectedness to Nature Ratings
Participants will complete ratings of their feelings of connectedness to nature after watching a brief (\~20 minute) nature video.
Time frame: This outcome will be assessed during both sessions, within two hours post-treatment.
Connectedness to Humanity Ratings
Participants will complete ratings of their feelings of connectedness to humanity after watching a brief (\~20 minute) nature video.
Time frame: This outcome will be assessed during both sessions, within two hours post-treatment.
Connectedness to Close Others Ratings
Participants will complete ratings of their feelings of connectedness to close others after watching a brief (\~20 minute) nature video.
Time frame: This outcome will be assessed during both sessions, within two hours post-treatment.
Baseline (T0) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). There are ten items, grouped into five subscales assessing anxiety-comfort, depression-pleasure, boredom-enthusiasm, tiredness-vigor, and anger-calmness. Individual items within bipolar subscales are appropriately reverse-scored so that higher scores consistently reflect greater affective well-being. Subscale scores are calculated by averaging the corresponding item pairs for each of the five factors, yielding five distinct state-affect indices.
Time frame: This outcome will be assessed during both sessions immediately after their vaping session.
Post-Treatment (T1) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). There are ten items, grouped into five subscales assessing anxiety-comfort, depression-pleasure, boredom-enthusiasm, tiredness-vigor, and anger-calmness. Individual items within bipolar subscales are appropriately reverse-scored so that higher scores consistently reflect greater affective well-being. Subscale scores are calculated by averaging the corresponding item pairs for each of the five factors, yielding five distinct state-affect indices.
Time frame: This outcome will be assessed during both sessions immediately after their vaping session.
Post-Cognitive Assessment (T2) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). There are ten items, grouped into five subscales assessing anxiety-comfort, depression-pleasure, boredom-enthusiasm, tiredness-vigor, and anger-calmness. Individual items within bipolar subscales are appropriately reverse-scored so that higher scores consistently reflect greater affective well-being. Subscale scores are calculated by averaging the corresponding item pairs for each of the five factors, yielding five distinct state-affect indices.
Time frame: This outcome will be assessed during both sessions immediately after their vaping session.
Post-Nature Video (T3) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). There are ten items, grouped into five subscales assessing anxiety-comfort, depression-pleasure, boredom-enthusiasm, tiredness-vigor, and anger-calmness. Individual items within bipolar subscales are appropriately reverse-scored so that higher scores consistently reflect greater affective well-being. Subscale scores are calculated by averaging the corresponding item pairs for each of the five factors, yielding five distinct state-affect indices.
Time frame: This outcome will be assessed during both sessions immediately after their vaping session.
Calories Consumed
The total number of calories participant consume will be recorded
Time frame: Every 30 minutes following the completion of cognitive and affect testing
Carbohydrates consumed
The total number of grams of carbohydrates participant consume will be recorded
Time frame: Every 30 minutes following the completion of cognitive and affect testing
Fat Consumed
The total number of grams of fat participant consume will be recorded
Time frame: Every 30 minutes following the completion of cognitive and affect testing
Protein Consumed
The total number of grams of protein participant consume will be recorded
Time frame: Every 30 minutes following the completion of cognitive and affect testing
Taste Ratings
Taste ratings will be collected for each food item they consume and the average of these ratings will be computed
Time frame: Every 30 minutes following the completion of cognitive and affect testing
Baseline (T0) Intoxication Rating
Participants will be asked to rate how high they feel using a scale from 0 (not high at all) to 10 (extremely high) prior to completing any study tasks.
Time frame: This outcome will be assessed during both sessions at baseline (i.e., during the testing session but before treatment).
Post-Session Intoxication Ratings
Participants will be asked to rate how high they feel using a scale from 0 (not high at all) to 10 (extremely high) while relaxing and sobering up, following the rest of their session.
Time frame: This outcome will be assessed every 30 minutes from 2 hours post-dose through 4 hours post-dose (or until the participant reports sobriety, whichever occurs later).
Vaping Session - Inhalation/Hold Duration
The principal investigator supervising the vaping session will record the duration of the participant's inhalations and holds during the vaping session.
Time frame: This outcome will be assessed during the vaping session (i.e., from the beginning of the vaping session until the end of the vaping session) during both sessions. This vaping session will occur immediately after the baseline assessments.
Vaping Session - Total Puffs
The principal investigator supervising the vaping session will record the total number of puffs the participant inhales.
Time frame: This outcome will be assessed during the vaping session (i.e., from the beginning of the vaping session until the end of the vaping session) during both sessions. This vaping session will occur immediately after the baseline assessments.
Cannabis Consumption Patterns
As part of their baseline assessments, participants will complete the Daily Sessions, Frequency, Age of Onset, and Quantity of Cannabis Use Inventory, which is a standardized, valid, and reliable measure of their cannabis consumption patterns. The information from this survey will be used to characterize the sample and determine cannabis use-related covariates that should be controlled for in analyses.
Time frame: This outcome will be assessed at baseline (i.e., during the testing session but before treatment).
Depression - Center for Epidemiologic Studies Depression Scale
As part of their baseline assessments, participants will complete the Center for Epidemiologic Studies Depression Scale. Higher scores indicate more frequent and more severe depressive symptoms. Potential scores range from 0-60. The information from this survey will be used to characterize the sample and determine potential covariates that should be controlled for in analyses.
Time frame: This outcome will be assessed at baseline (i.e., during the testing session but before treatment).
Anxiety - Beck Anxiety Inventory
As part of their baseline assessments, participants will complete the Beck Anxiety Inventory. Higher scores indicate greater anxiety severity. Potential scores range from 0-63. The information from this survey will be used to characterize the sample and determine potential covariates that should be controlled for in analyses.
Time frame: This outcome will be assessed at baseline (i.e., during the testing session but before treatment).
ADHD Symptoms - Barkley Adult ADHD Rating Scale - IV
As part of their baseline assessments, participants will complete the Barkley Adult ADHD Rating Scale (IV). Higher scores indicate greater ADHD symptom frequency and severity. Potential scores range from 0-54. The information from this survey will be used to characterize the sample and determine potential covariates that should be controlled for in analyses.
Time frame: This outcome will be assessed at baseline (i.e., during the testing session but before treatment).
Emotion Regulation - Difficulties in Emotion Regulation Scale
As part of their baseline assessments, participants will complete the Difficulties in Emotion Regulation Scale. Higher scores indicate greater difficulties with emotion regulation across domains. Potential scores range from 36-180. The information from this survey will be used to characterize the sample and determine potential covariates that should be controlled for in analyses.
Time frame: This outcome will be assessed at baseline (i.e., during the testing session but before treatment).
Dynamic Cognitive Flexibility - Think Aloud Task
Participants verbalize their spontaneous thoughts for five minutes while being audio recorded. Recordings are transcribed and segmented into individual thought units, which are grouped into topics using natural language processing. Thought patterns are characterized by the frequency and transitions between topics, including the degree of similarity between successive thoughts.
Time frame: This outcome will be assessed at the end of the session during both sessions.
Event-Based Prospective Memory - Difficulty Ratings
Event-based prospective memory will be assessed using a difficulty ratings task. At the beginning of the session, participants will be asked to try to remember to rate how difficult they found each test immediately after it is completed, using a 0 (not at all difficult) to 10 (extremely difficult) scale. Other outcomes of this task are the self-reported difficulty of each task completed.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cognitive Flexibility - Probabilistic Reversal Learning Task, Win-Stay/Lose-Shift Behavior
Probabilistic reversal learning will be assessed using a computerized task in which participants select between two stimuli associated with different probabilities of receiving positive feedback. Participants will learn the more advantageous choice based on probabilistic feedback and must adjust their responses when the relative probabilities of the stimuli are reversed. Other outcomes of this task will be the proportion of trials on which participants repeat a previously rewarded choice ("win-stay") and the proportion of trials on which participants switch choices following negative feedback ("lose-shift"). Lower win-stay and/or lose-shift proportions indicate reduced use of feedback to guide subsequent choices.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cognitive Flexibility - Probabilistic Reversal Learning Task, Reversal Errors
Probabilistic reversal learning will be assessed using a computerized task in which participants select between two stimuli associated with different probabilities of receiving positive feedback. Participants will learn the more advantageous choice based on probabilistic feedback and must adjust their responses when the relative probabilities of the stimuli are reversed. Other outcomes on this task include the number of reversal errors, defined as incorrect choices made following a reversal in the stimulus-outcome contingencies. Higher reversal error scores indicate poorer reversal learning.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cognitive Flexibility - Verbal Fluency, Category Switching Fluency
Cognitive flexibility (category switching) will be assessed using the verbal fluency category switching task. Participants will be given two categories (e.g., fruits and furniture) and be asked to generate words that belong to those categories, in alternating order, within a time limit of 60 seconds. Other outcomes on this task include the category fluency score, which is the number of correct words generated.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Cogntiive Flexibility - Verbal Fluency, Category Switching Errors
Cognitive flexibility (category switching) will be assessed using the verbal fluency category switching task. Participants will be given two categories (e.g., fruits and furniture) and be asked to generate words that belong to those categories, in alternating order, within a time limit of 60s. Other outcomes on this task include repetition and intrusion (i.e., non-category words) errors.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Working Memory Updating - N-Back Reaction Time
Cognitive flexibility and working memory updating will be assessed using the N-back test. Participants are shown strings of letters one at a time and are instructed to indicate whenever a letter appears that matches the letter shown two trials earlier. Other outcomes include the mean reaction time (milliseconds) for correct responses on the task.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Planning - Tower Test Rule Violations
Planning and problem-solving abilities will be assessed using the Tower Test. Participants are asked to move disks to reach a specified end configuration in as few moves as possible. They can move only one disk at a time and cannot place a larger disk on top of a smaller disk. Other outcomes on this task include the number of rule violations (e.g., moving stacking a larger disk on top of a smaller one).
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Planning - Tower Test Time to Completion
Planning and problem-solving abilities will be assessed using the Tower Test. Participants are asked to move disks to reach a specified end configuration in as few moves as possible. They can move only one disk at a time and cannot place a larger disk on top of a smaller disk. Other outcomes on this task include the time taken to complete each tower problem.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Planning - Zoo Maps Test Rule Violations
Planning and strategic thinking will be assessed using the Zoo Maps Test. Participants must plan a route through a provided zoo map while adhering to specified rules and efficiency constraints. For example, they may be instructed to start at the entrance, end at the picnic area, and use the designated paths only once. Other outcomes on this task include the number of rule violations on the task.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Inhibitory Control - Stroop Test Accuracy
Inhibitory control will be assessed using the Stroop test. Participants will be shown words whose letters are in a specific color (e.g., the word "blue" in red letters. They will be tasked with naming the color of the word, which may be incongruent with the word itself. Other outcomes on this task include the percentage of correct responses on incongruent trials.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Inhibitory Control - Go/No-Go Commission Errors
Inhibitory control will be assessed using a computerized Go/No-Go task. Participants will respond as quickly and accurately as possible to designated "Go" stimuli and withhold their response when designated "No-Go" stimuli are presented. Other outcomes will be the number of commission errors, defined as responses made to No-Go stimuli. Higher commission error scores indicate poorer inhibitory control.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Inhibitory Control - Stroop Test ERP
Inhibitory control will be assessed using the Stroop test. Participants will be shown words whose letters are in a specific color (e.g., the word "blue" in red letters. They will be tasked with naming the color of the word, which may be incongruent with the word itself. The Muse S Athena wearable EEG device will capture time-locked event-related potential data during this task.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Working Memory Updating - N-Back ERP
Cognitive flexibility and working memory updating will be assessed using the N-back test. Participants are shown strings of letters one at a time and are instructed to indicate whenever a letter appears that matches the letter shown two trials earlier. The Muse S Athena wearable EEG device will capture time-locked event-related potential data during this task.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
Inhibitory Control - Go/No-Go ERP
Inhibitory control will be assessed using a computerized Go/No-Go task. Participants will respond as quickly and accurately as possible to designated "Go" stimuli and withhold their response when designated "No-Go" stimuli are presented. The Muse S Athena wearable EEG device will capture time-locked event-related potential data during this task.
Time frame: This outcome will be assessed during both sessions, within 90 minutes post-treatment.
EEG Power
The Muse S Athena wearable EEG device will be worn by participants for the duration of the session, up until they are left to relax and sober up at the end of the session. The EEG device will be continuously recording, to allow for later quantification of power (e.g., theta, gamma, etc.) using spectral density analysis.
Time frame: This outcome will be continuously assessed during both sessions, from baseline (i.e., during the testing session but before treatment) through two hours post-treatment.
Baseline (T0) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). The ten items will be analyzed separately as an exploratory outcome.
Time frame: This outcome will be assessed during both sessions at baseline (i.e., during the testing session but before treatment).
Post-Treatment (T1) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). The ten items will be analyzed separately as an exploratory outcome.
Time frame: This outcome will be assessed during both sessions at baseline (i.e., during the testing session but before treatment).
Post-Cognitive Assessment (T2) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). The ten items will be analyzed separately as an exploratory outcome.
Time frame: This outcome will be assessed during both sessions at baseline (i.e., during the testing session but before treatment).
Post-Nature Video (T3) Daniels Five-factor Measure of Affective Well-being (D-FAW) Subscale Scores
Participants will be asked to rate the intensity of each affective state experienced at the current moment using a 6-point Likert scale ranging from 1 (Not at all) to 6 (Very much). The ten items will be analyzed separately as an exploratory outcome.
Time frame: This outcome will be assessed during both sessions at baseline (i.e., during the testing session but before treatment).
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: Yes — De-identified data will be shared upon request and after publication of our primary findings.
Supporting information: Study protocol, Statistical analysis plan
Time frame: The study protocol and statistical analysis plan will be available from October 2026 onwards
Access criteria: The IPD will be available upon email request to one of the PIs on this study. De-identified data and the study protocol, statistical analysis plan, and informed consent form can/will be shared upon request.
Started Sep 2026 (actual). Primary completion is estimated for May 2028, 20 months after the start.
Start moved once since we started tracking on Sep 25, 2026: Jul 2026 → Sep 2026, on Sep 29, 2026.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Dronabinol
Washington State University