Table 9.
Overview of the effects of time, and group-by-time effects on white matter, in longitudinal studies of cannabis users and controls, and their association with cannabis exposure levels and other variables.
| References | Baseline age (yrs) | Follow-up period | Effect of time and group × time | Brain-behavior correlations |
|---|---|---|---|---|
| Lichenstein et al. (2022) | 20 | 2 yrs | FA (group-by-time) lower ↑↑ cingulum in moderately extended cannabis vs control | n.s. onset age, duration and frequency |
| Becker et al. (2015) | 20 | 2 yrs | FA (group-by-time) lower ↑↑ in SLF (next to junction with corticospinal tract), SLF (ext. to corpus callosum forceps major), superior frontal gyrus, in cannabis vs. controls. trend lower ↑↑ in corticospinal tract (adj. to precentral and postcentral gyri) and anterior thalamic radiations; superior fronto-occipital fasciculus (adj. to frontal operculum) greater ↑↑ in corpus callosum (ant.), thalamus (adj. to post.), in cannabis vs. controls. RD (group-by-time) lower ↑↑ in SLF, corticospinal tract and cingulum (post.), in cannabis vs. controls. higher ↑↑ corticospinal tract in cannabis vs. controls. | neg. cor. cannabis hits/past year and FA change of corticospinal tract, SLF/corpus callosum and forceps major. neg cor. max. frequency of cannabis hits/past year and FA change of SLF/corticospinal tract n.s. cor. age of onset and RAVLT |
| Epstein and Kumra (2015) | 17 | 1.5 yrs | FA (group-by-time) ↓↓ inferior longitudinal fasciculus in cannabis and ↑↑ controls trend ↓↓ inferior fronto-occipital fasciculus in cannabis vs controls FA (time) ↓↓ inferior longitudinal fasciculus in cannabis users | Neg. cor. total days cannabis use days over time and ↓↓FA of inferior longitudinal fasciculus |
| Jacobus et al. (2013a) | 18 | 3 yrs | FA (time) ↓↓ corpus callosum (splenium), inferior fronto-occipital fasciculus, anterior thalamic radiations, uncinate fasciculus, SLF, corona radiata (ant., sup.), internal capsule (posterior limb). ↓↓ corpus callosum (genu), anterior thalamic radiations, and SLF. | Pos. cor. change in global neurocognition over time and FA SLF at follow-up |
| Jacobus et al. (2013b) | 18 | 1.5 yrs | - | Baseline ↓ FA in fornix and sup. corona radiata predicted more cannabis use days and delinquent/aggressive risk taking at follow-up. |
Adj, adjacent; Ant, anterior; Cor, correlated; FA, fractional anisotropy; Mage, mean age; Max., maximum; neg, negative; n.s., non-significant Pos, positive; Post, posterior; RAVLT, Rey Auditory Verbal Learning Test; SLF, superior longitudinal fasciculus; Sup, superior; yrs, years; -, not reported, ↑↑ increase over time; ↓↓ decrease over time.