Regular cannabis use is associated with altered activation of central executive and default mode networks even after prolonged abstinence in adolescent users: Results from a complementary meta-analysis

Abstract

Whether the effects of cannabis use on brain function persist or recover following abstinence remains unclear. Therefore, using meta-analytic techniques, we examined whether functional alterations measured using fMRI persist in cannabis users abstinent for over 25 days (or 600 h) as evidence suggests that the effects on cognitive performance no longer persist beyond this period. Systematic literature search identified 20 studies, of which, 12 examined current cannabis users (CCU) (361 CCU versus 394 non-cannabis using controls (NU)) and 3 examined abstinent cannabis users (ACU) in 5 separate comparisons (98 ACU versus 106 NU). Studies in ACU were carried out in adolescents and suggest significantly greater activation in components of the central executive and default mode networks in adolescent ACU compared to NU. While this evidence is to be interpreted with caution because studies were carried out in overlapping samples, they indicate a pressing need for independent confirmation whether certain neurofunctional alterations in adolescent cannabis users may persist even after cannabis and its metabolites are likely to have left their bodies.

Keywords: Abstinence; Cannabis; Functional magnetic resonance imaging; Meta-analysis; THC.

Fig. 1

Flow-chart showing the identification, classification and inclusion of papers selected for meta-analysis. *One paper included two studies, one of which was eligible for inclusion, one of which was excluded.

Fig. 2

Maps of statistically significant differences in activation (Voxel threshold = p < 0.005, peak height threshold: peak SDM-Z < 1, clusters ≥ 10). Axial brain slice position shown on a sagittal view bottom right, with slices arranged from left to right in the different panels showing brain slices in ascending order from bottom to top. A - Activation of current CU compared to non-using control subjects, increased activation in CU shown in red, decreased activation in CU shown in blue (k = 22; CU n = 361, NU n = 394). B - Activation of adolescent abstinent CU compared to non-using controls, increased activation in CU shown in red (k = 5; CU n = 98, NU n = 106). C - Activation of adolescent abstinent CU compared to current adult and adolescent CU, increased activation in abstinent users shown in red (CCU: k = 22, n = 361; ACU: k = 5, n = 98). D - Adolescent current CU compared to non-using controls, increased activation in CU shown in red (k = 4; CU n = 69, NU n = 70).