Heavy cannabis use, dependence and the brain: a clinical perspective

Abstract

Aims To summarize and evaluate our knowledge of the relationship between heavy cannabis use, cannabis use disorder (CUD) and the brain. Methods Narrative review of relevant literature identified through existing systematic reviews, meta‐analyses and a PubMed search. Epidemiology, clinical representations, potential causal mechanisms, assessments, treatment and prognosis are discussed. Results Although causality is unclear, heavy and dependent cannabis use is consistently associated with a high prevalence of comorbid psychiatric disorders and learning and memory impairments that seem to recover after a period of abstinence. Evidence regarding other cognitive domains and neurological consequences, including cerebrovascular events, is limited and inconsistent. Abstinence after treatment is only achieved in a minority of cases; treatment targeted at reduction in use appears have some success. Potential moderators of the impact of CUD on the brain include age of onset, heaviness of use, CUD severity, the ratio of ∆9‐tetrahydrocannabinol to cannabidiol and severity of comorbid disorders. Conclusions Current evidence of long‐term effects of daily cannabis use and cannabis use disorder on brain‐related outcomes is suggestive rather than conclusive, but use is associated with psychiatric morbidity and with cognitive impairments that recover after a period of abstinence.

A genetically-informed study disentangling the relationships between tobacco smoking, cannabis use, alcohol consumption, substance use disorders and respiratory infections, including COVID-19

“…Regarding cannabis use, to our knowledge this is the first MR study to investigate the role of cannabis use in respiratory infections, and while we failed to find evidence of any relationships, smoking cannabis, like tobacco smoking, may prompt the onset of coughing, which could consequently increase viral transmission, or may exacerbate possibly respiratory symptoms. As cannabis is the most used drug worldwide –an estimated 188 million recreational users worldwide 58 – this aspect of cannabis use may have important implications for the spread of COVID-19. In contrast, the single-variable MR CUD results demonstrated adverse effects on several respiratory outcomes, but not COPD, which supports the existing literature; 59-61 however, accounting for lifetime tobacco smoking attenuated highlighting the complex nature of these relationships.…”

Cannabis Use in People With Obsessive-Compulsive Symptomatology: Results From a Mexican Epidemiological Sample

“…Currently, the main pharmacological treatment for OCD is serotonin reuptake inhibitors, and the search for new treatments and growing approval of THC derivatives has produced favorable results in case studies (17). However, we cannot disregard the relationship between cannabis use and the development of dependence (18)(19)(20), which is inheritable, complex, and associated with mental health disorders (21,22). A recent study explored genetic factors associated with lifetime use of cannabis and found ∼35 genes in a sample of more than 180,000 individuals (23).…”

HIV infection is linked with reduced error-related default mode network suppression and poorer medication management abilities

“…HIV crosses the blood brain barrier, replicates, and infects cells in the central nervous system (CNS), leading to neuroinflammation and neural degeneration [1][2][3]. Neuroimaging has identified structural and functional brain alterations linked with HIV infection, particularly in frontostriatal circuitry [4][5][6][7][8][9], that are thought to contribute to a spectrum of progressive neurocognitive declines characterizing the disease [10][11][12][13][14][15]. Even with widespread availability of antiretroviral therapy, approximately 30-50% of persons living with HIV (PLWH) are impacted by neurocognitive alterations [16,17].…”