A Different Patterns of EEG Transmission in Individuals with Cannabis and Polydrug Use: A Directed Transfer Function Approach.

Rationale and Objectives Cannabis is often used in polydrug contexts, yet research comparing its isolated use to polydrug use is limited. Such studies could provide ecologically valid insights into their distinct effects on brain activity. This study examines the impact of cannabis and polydrug use on resting-state EEG patterns using Directed Transfer Function (DTF) analysis to assess frequency-dependent brain activity propagation. Methods Three groups were studied: cannabis users (n=27), polydrug users (n=29), and non-drug-using controls (n=30), matched for age and sex. Resting-state EEG was recorded with eyes open and closed. DTF was used to assess directed connectivity and frequency-dependent EEG signal transmission within brain networks. Results DTF revealed distinct alterations in neural connectivity among individuals with cannabis use, characterized by local changes of propagation in frontal regions, particularly in theta, beta, and gamma bands, with relatively unchanged alpha band activity. Adults with polydrug use history demonstrated more complex EEG propagation and more pronounced alterations of transmission patterns, including decreased alpha activity and increased frontal and prefrontal activity, suggesting heightened excitation and a probable compensation mechanism. Conclusions This study is the first to identify frequency-specific cortical connectivity patterns linked to cannabis and polydrug use. Findings highlight the importance of studying substance use patterns and considering cannabis within a polysubstance context. A longitudinal study is needed to assess the effects of use duration, frequency, and dosage.