Neurobehavioral Impacts of Medical Cannabis Use: An Observational Study

Summary

This study will assess cognition, neural function, and drug exposure in chronic pain patients who have been prescribed medical cannabis and will differentiate outcomes based on use of specific CBD-dominant versus THC-dominant treatment products. This longitudinal study will recruit medical cannabis users from local dispensaries. Each participant will complete a baseline assessment prior to the start of medical cannabis use, monthly phone calls to assess treatment adherence, and a four-month follow- up assessment. The aims of this project are: Aim 1. To assess impacts of medical cannabis compounds on executive functions, learning and memory in adults to determine whether cognitive impairments are evident after the onset of cannabis use; Aim 2. To assess the impacts of medical cannabis compounds on white matter microstructure, functional brain activity and functional connectivity; Aim 3. To differentiate change over four months in these outcomes as a function of (a) age and (b) pre-to-post-treatment changes in blood levels of cannabinoid compounds.

Description

Eligibility

Age range

35–65 years

Sex

All

Healthy volunteers

No

Interventions

• Behavioral
  Cognitive testing

  Participants will complete a cognitive testing battery that includes measures of attention, learning, memory, problem-solving and executive function.

• Behavioral
  Task-based fMRI measure of inhibitory control

  All participants will complete a task-based fMRI measure of inhibitory control. This Go/No-Go task provides a contrast of BOLD signals when response conflict is low (execution of motor responses on frequent Go trials) vs high (inhibiting the prepotent response on infrequent NoGo trials). It will provide an assessment of the effects of cannabis use on the frontostriatal implicit motor learning and cognitive control systems. Participants view shapes and press a button quickly (Go trials) to every shape except circles and squares (NoGo Trials). To increase response prepotency, Go trials are frequent (75%). Button presses must be rapid to be considered correct. The task uses an event-related design with each stimulus presented for 600 ms, followed by a 1.0-4.5 second jittered ISI during which a white fixation crosshair is displayed. Trial type is pseudo-randomized with the constraint of equal frequencies of consecutive Go trials (2, 3, or 4) between NoGo trials.

• Behavioral
  Task-based fMRI measure of face-name learning

  This task is ideally suited to assess cannabis effects on explicit associative learning and memory as mediated by frontohippocampal networks. Participants memorize names corresponding to faces (encoding phase), and then recall the names after a short delay. The first encoding block begins with a 2-second cue ("MEMORIZE") followed by 5 face-name pairs, each shown for 4 seconds; participants press a button when they encode each face-name pair. A distractor block follows. Next, a retrieval block begins with a cue to "RECALL" followed by presentations of each of the same 5 faces, now paired with "???" (i.e., prompting recall of previously paired names), with a 4 second stimulus duration and no ISI. On recall trials, participants press a button to indicate that they have recalled the name for the displayed face. Participants engage in silent uncued recall of face-name pairs. Immediately following the scan, participants are tested for accuracy of name retrieval.

Location