A study recently published in the journal NeuroImage suggests regular marijuana use can leave you with a "noisy" brain.
A team of researchers at the University of Texas at Dallas used electroencephalography to monitor the brain activity of 38 volunteers (17 regular marijuana users and 21 non-users) when they were in a resting state. This is apparently the first experiment to measure brainwaves in marijuana users when they are not engaged in a task.
The results show that yes, regular marijuana use leaves marks on the brain, even when you're sober. Specifically, they found it can increase cortical activity and connectivity, supporting other studies that have shown chronic pot smoking increases connections between different brain regions. This sounds like a good thing. (After all, creativity has been linked to stronger connections.) But the researchers say all this extra activity results in a "noisy" brain that has lost some of its neural efficiency. Oh.
While marijuana use was associated with greater theta, beta, and gamma wave activity, it was also linked to decreased delta wave activity. Delta waves are the high-amplitude, low-frequency waves associated with deep, dreamless sleep, whereas theta, beta, and gamma waves are all lower in amplitude and higher in frequency than delta waves, and, therefore, associated with a more alert brain state.
These changes in neural activity may relate to some of the cognitive impairments associated with marijuana use, Shikha Prashad, lead author and a postdoctoral student at the University of Texas at Dallas told PsyPost.
To keep things fair and ensure remnants of the drug weren't tainting the results, the users were asked to abstain from lighting up in the 24 hours prior to the study. Though, clearly, not everybody got the memo.
“We did collect information on time since last use, which ranged from 12 to 60 hours, and found no associations with neural activity, indicating that the effects were likely related to the ongoing cannabis use, but this should be verified,” Prashad told PsyPost.
It does, however, mean that these results show only the very short-term effects of marijuana use, which may not remain consistent over a longer-term follow-up study.
It is also unclear at this stage whether the changes in brain activity are a direct effect of the drug itself or a consequence of substance use more generally. As with a lot of research that delves into marijuana use, the study is correlational rather than causational.