Mobile phone cognitive tests detected slight impairment from marijuana in young adults' daily lives | Research

The takeaway

Young adults who reported feeling more high from marijuana performed slightly worse on mobile phone cognitive tests in their natural environments, with slower reaction times and fewer correct responses.

Cannabis users interested in impairment awareness, cognitive researchers, app developers

Higher subjective marijuana high linked to slower reaction times on all 3 mobile tasks

What the researchers found

Higher subjective marijuana ratings were associated with slower reaction times on all three mobile tasks (Flowers: B=2.29, p=.008; Stroop: B=2.74, p=.01; DSST: B=3.08, p=.03) and fewer correct responses on two of three tasks. Distraction moderated the association for some tasks.

Why it matters

Traditional lab studies of cannabis impairment may not capture real-world effects. Mobile assessment in natural environments provides ecologically valid data on how marijuana affects daily cognitive functioning.

The numbers in context

60 participants; 2,703 data points; 451 (16.7%) marijuana use reports. Significant slowing on all 3 tasks. Significant accuracy decreases on 2 of 3 tasks. Effects described as "slight" decreases in cognitive functioning.

How the study worked

Observational study of 60 young adults (aged 18-25) who used marijuana at least twice weekly. Mobile cognitive tasks (visuospatial working memory, attentional bias, processing speed) delivered 3 times daily plus self-initiated during marijuana use, for up to 30 days. 2,703 data points collected including 451 marijuana use reports.

What this study cannot tell us

Small sample; self-reported marijuana ratings; no objective THC measurement; participants were regular users who may have developed tolerance; "slight" effects may not be clinically meaningful.

How to read the evidence

Observational study with ecological validity but no controlled dosing or objective impairment measures.

When this study was published

Published in 2020.

The bigger picture

Real-time mobile cognitive monitoring could eventually provide immediate feedback to cannabis users about their functional impairment, helping them make decisions about driving or other activities.

Questions still open

Could real-time cognitive monitoring apps serve as practical impairment self-checks? Would effects be larger in less frequent users?

Common questions

How impaired were people who felt high?

The effects were described as "slight" decreases in cognitive functioning. Higher subjective ratings of being high were associated with a few milliseconds slower reaction time and slightly fewer correct answers. These are statistically significant but may not represent major functional impairment.

Could a phone app detect marijuana impairment?

This study provides proof-of-concept that mobile cognitive tasks can detect acute marijuana effects in real-world settings. However, the effects were small and there was considerable overlap between impaired and non-impaired performance, so practical application would need further development.

Read the original research

Mobile Assessment of Acute Effects of Marijuana on Cognitive Functioning in Young Adults: Observational Study.

JMIR mHealth and uHealth, 8(3), e16240

View on PubMed ↗Publisher’s paper ↗

Citation

Chung, Tammy; Bae, Sang Won; Mun, Eun-Young; Suffoletto, Brian; Nishiyama, Yuuki; Jang, Serim; Dey, Anind K. (2020). Mobile Assessment of Acute Effects of Marijuana on Cognitive Functioning in Young Adults: Observational Study.. JMIR mHealth and uHealth, 8(3), e16240. https://doi.org/10.2196/16240