Motion and form perception in healthy individuals with adolescent cannabis use.

Barko B.; Kéri S. · Frontiers in psychiatry · 2026

**Background & Methods** This cross-sectional study examined 130 abstinent adults (cannabis-naïve controls n=50, non-heavy adolescent users n=38, heavy adolescent users n=42) to assess whether heavy cannabis use during early adolescence causes lasting deficits in visual perception. Participants had no current substance use and were in remission from cannabis-related problems for ≥12 months, with exclusion of DSM-5 psychiatric disorders. Motion coherence thresholds were measured using random-dot displays, and form coherence thresholds using orientation-defined circles; cannabis exposure was quantified using the Cannabis Exposure Inventory (CEI). **Key Findings** - Heavy adolescent cannabis users demonstrated significantly higher motion coherence thresholds compared to controls and non-heavy users (p < 0.001; Bayes Factor >10, indicating strong evidence), indicating selective impairment in global motion perception despite complete abstinence. - Form coherence thresholds did not differ between groups, demonstrating selective sparing of global form perception and suggesting dorsal visual stream vulnerability rather than generalized visual processing deficits. - Non-heavy adolescent users showed no perceptual differences from cannabis-naïve controls, and CEI scores predicted motion coherence thresholds, supporting a dose-response relationship between early heavy cannabis exposure and enduring motion perception deficits. **Dosage & Administration** Heavy adolescent use was defined as daily cannabis consumption beginning before age 15. Specific doses, frequency, duration, or routes of administration were not reported. **Safety & Adverse Effects** Not reported. The study focused on cognitive/perceptual outcomes rather than acute or chronic adverse effects. **Evidence Quality** This study provides moderate evidence with several limitations. The cross-sectional design prevents causal inference; longitudinal studies are needed to establish developmental trajectories. Reliance on retrospective self-reported cannabis exposure via CEI introduces recall bias and potential underreporting. The relatively small sample size and exclusion of participants with psychiatric comorbidities limits generalizability. However, the study employs rigorous neuropsychological testing with quantitative thresholds, strong Bayesian statistical support, and addresses a specific mechanistic hypothesis (dorsal stream vulnerability). The selective impairment pattern (motion but not form) strengthens the specificity of findings. Findings would benefit from neuroimaging confirmation and longitudinal validation.

More recent cannabis research