Cannabinoids and cognition in Parkinson's disease: Insights from animal models and emerging clinical evidence.

Abstract

Parkinson's disease (PD) is a progressive, multisystem neurodegenerative disorder characterized not only by motor impairments but also by a broad spectrum of debilitating non-motor symptoms, including cognitive decline. The cognitive function depends on neuronal plasticity, which is tightly regulated by multiple signaling systems, among which the endocannabinoid system (ECS) plays a significant role. Over the past three decades, substantial evidence has accumulated regarding how endogenous cannabinoids, plant-derived cannabinoids, and pharmacological modulators of ECS signaling influence synaptic plasticity, neuronal excitability, and neuroinflammation - processes that are critical in PD pathophysiology. This narrative review synthesizes experimental and clinical evidence on the effects of cannabinoid compounds on cognition in preclinical PD models and patients. Available clinical data are limited, heterogeneous, and often underpowered, with cognition frequently assessed as a secondary outcome. Observed variability in cognitive effects likely reflects differences in cannabinoid formulation, dose and treatment duration, study design, patient characteristics, and the use of heterogeneous cognitive endpoints across studies. Cannabinoid-based interventions hold promise for preserving neural circuits and modulating cognitive function in PD; however, well-designed, mechanism-informed trials with standardized, domain-specific cognitive endpoints are essential before clinical recommendations can be made.