Psychiatric Disorders and Cannabis Use: Mechanisms of Action and Long-Term Risks

Abstract

In recent decades, cannabis use has gained growing interest from both the scientific community and the general public, driven by legalization movements and recognition of its potential therapeutic effects. However, alongside these advances, increasing evidence has emerged regarding the adverse impacts of cannabis on mental health. Studies have shown a significant association between regular cannabis use and the development of various psychiatric disorders, such as schizophrenia, anxiety disorders, depression, and bipolar spectrum disorders.

The neurobiological mechanisms by which cannabis affects mental health primarily involve the endocannabinoid system, which regulates functions such as mood, cognition, appetite, and sleep. Δ9-tetrahydrocannabinol (THC), the main psychoactive compound in cannabis, acts as a partial agonist of CB1 receptors, which are highly expressed in brain regions such as the hippocampus, prefrontal cortex, and basal ganglia. Activation of these receptors may alter dopaminergic, glutamatergic, and GABAergic neurotransmission, contributing to the onset or worsening of psychiatric symptoms, particularly in individuals with genetic vulnerability.

Longitudinal evidence indicates that early, frequent use and high THC concentrations are associated with an increased risk of psychosis and may accelerate the clinical manifestation of psychiatric disorders in predisposed individuals. In contrast, cannabidiol (CBD), another major cannabinoid, has attracted interest for its potential anxiolytic and antipsychotic properties, although clinical data remain limited. The ratio of THC to CBD in consumed products appears to be a key factor influencing psychiatric outcomes and is an ongoing area of investigation.

From a clinical standpoint, cannabis-induced psychiatric disorders pose diagnostic and therapeutic challenges. Chronic use may compromise treatment adherence, interfere with the effectiveness of psychotropic medications, and hinder clinical stabilization. Moreover, the risk of cannabis dependence and withdrawal syndrome—although lower than that of other substances—is real and must be considered, especially in adolescents and young adults.

Given this context, careful assessment of substance use history, along with early screening for psychiatric symptoms, is essential in clinical practice. Public health education campaigns targeting at-risk populations should emphasize the potential adverse mental health effects of cannabis, particularly when used at a young age or in high quantities.

In summary, although cannabis may offer therapeutic potential, recreational or indiscriminate use represents a significant risk factor for the development of psychiatric disorders. Understanding the underlying mechanisms, identifying vulnerable individuals, and implementing prevention and early intervention strategies are crucial to mitigating the long-term harms of cannabis use and ensuring a safer, more informed approach for both patients and mental health professionals.