Cannabis and Mental Health: A Systematic Review and Meta-analysis of the Neuropsychiatric Effects, Therapeutic Potentials, and Policy Implications of THC and CBD
Article Sidebar
Main Article Content
Abstract
Aim: This systematic review and meta-analysis examined the neuropsychiatric effects of cannabis, focusing on the contrasting roles of Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). It evaluated their associations with psychiatric outcomes, assessed the therapeutic potential of cannabis-based products (CBPs), and identified evidence gaps relevant to clinical practice and mental health policy.
Methods: The review was conducted in accordance with PRISMA guidelines. Electronic databases (PubMed, Scopus, Web of Science, Cochrane Library, and Google Scholar) were searched for studies published between 2005 and 2025. Eligible studies included randomized controlled trials, observational studies, mixed-methods studies, and systematic reviews investigating the psychiatric or neuropsychological effects of THC, CBD, or CBPs. Study quality was assessed using the Joanna Briggs Institute critical appraisal tools. Meta-analysis was performed where appropriate, and narrative synthesis was used for heterogeneous outcomes.
Results: Of 3,503 records identified, 14 studies met the inclusion criteria. THC was consistently associated with an increased risk of psychotic symptoms, cognitive impairment, and anxiety, whereas CBD demonstrated potential antipsychotic, anxiolytic, and neuroprotective effects. Evidence for CBPs in treating psychiatric disorders was limited, with modest short-term benefits but insufficient support for long-term efficacy. Small sample sizes, heterogeneous dosing regimens, and inconsistent outcome measures limited the strength of the evidence.
Conclusion: THC and CBD exhibit distinct neuropsychiatric profiles. Although CBD shows therapeutic promise, robust evidence supporting its long-term effectiveness in psychiatric care remains insufficient. Standardized clinical trials are needed to establish optimal dosing, evaluate long-term safety and efficacy, and inform evidence-based clinical guidelines and public health policies.
Article Details
Copyright (c) 2026 Okoroezi DO.
This work is licensed under a Creative Commons Attribution 4.0 International License.
Umana EA, Umana UE. The prevalence of substance abuse among youths: evaluating the implications on mental health and rape cases in our society. International Journal of Research in Education, Science and Technology. 2024;7(1): 45-59.
Calapai G, Mannucci C, Chinou I, Cardia L, Calapai F, Sorbara EE, et al. Preclinical and clinical evidence supporting use of cannabidiol in psychiatry. Evid Based Complement Alternat Med. 2019;2019:2509129. Available from: https://doi.org/10.1155/2019/2509129
Pressman P, Hayes AW, Hoeng J, Latino DA, Mazurov A, Schlage WK, et al. Δ9-Tetrahydrocannabinol (THC): a critical overview of recent clinical trials and suggested guidelines for future research. J Clin Med. 2024;13(6):1540. Available from: https://doi.org/10.3390/jcm13061540
Morgan CJ, Freeman TP, Hindocha C, Schafer G, Gardner C, Curran HV. Individual and combined effects of acute delta-9-tetrahydrocannabinol and cannabidiol on psychotomimetic symptoms and memory function. Transl Psychiatry. 2018;8(1):181. Available from: https://dx.doi.org/10.1038/s41398-018-0191-x
Theunissen EL, Reckweg JT, Hutten NRP, Kuypers KPC, Toennes SW, Neukamm MA, et al. Psychotomimetic symptoms after a moderate dose of a synthetic cannabinoid (JWH-018): implications for psychosis. Psychopharmacology (Berl). 2022;239(5):1251-61. Available from: https://doi.org/10.1007/s00213-021-05768-0
Crippa JA, Guimarães FS, Campos AC, Zuardi AW. Translational investigation of the therapeutic potential of cannabidiol (CBD): toward a new age. Front Immunol. 2018;9:2009. Available from: https://doi.org/10.3389/fimmu.2018.02009
Dammann I, Rohleder C, Leweke FM. Cannabidiol and its potential evidence-based psychiatric benefits: a critical review. Pharmacopsychiatry. 2024;57(3):115-32. Available from: https://doi.org/10.1055/a-2228-6118
Hall W, Stjepanović D, Caulkins J, Lynskey M, Leung J, Campbell G, et al. Public health implications of legalising the production and sale of cannabis for medicinal and recreational use. Lancet. 2019;394(10208):1580-90. Available from: https://doi.org/10.1016/s0140-6736(19)31789-1
Farber Y, Nir O, Farber S. Medicalization without legalization: the European policy for medical and recreational cannabis use. J Public Health. 2024;46(4):e560-e567.
McKee KA, Hmidan A, Crocker CE, Lam RW, Meyer JH, Crockford D, et al. Potential therapeutic benefits of cannabinoid products in adult psychiatric disorders: a systematic review and meta-analysis of randomized controlled trials. J Psychiatr Res. 2021;140:267-81. Available from: https://doi.org/10.1016/j.jpsychires.2021.05.044
Sarris J, Sinclair J, Karamacoska D, Davidson M, Firth J. Medicinal cannabis for psychiatric disorders: a clinically focused systematic review. BMC Psychiatry. 2020;20(1):24. Available from: https://doi.org/10.1186/s12888-019-2409-8
Ganesh S, Cortes-Briones J, Schnakenberg Martin AM, Skosnik PD, D'Souza DC, Ranganathan M. Delta-9-tetrahydrocannabinol, cannabidiol, and acute psychotomimetic states: a balancing act of the principal phytocannabinoids on human brain and behavior. Cannabis Cannabinoid Res. 2023;8(5):846-56. Available from: https://doi.org/10.1089/can.2021.0166
Ahmed S, Roth RM, Stanciu CN, Brunette MF. The impact of THC and CBD in schizophrenia: a systematic review. Front Psychiatry. 2021;12:694394. Available from: https://doi.org/10.3389/fpsyt.2021.694394
Moore TH, Zammit S, Lingford-Hughes A, Barnes TR, Jones PB, Burke M, et al. Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review. Lancet. 2007;370(9584):319-28. Available from: https://doi.org/10.1016/s0140-6736(07)61162-3
Sorkhou M, Dent EL, George TP. Cannabis use and mood disorders: a systematic review. Front Public Health. 2024;12:1346207. Available from: https://doi.org/10.3389/fpubh.2024.1346207
Black N, Stockings E, Campbell G, Tran LT, Zagic D, Hall WD, et al. Cannabinoids for the treatment of mental disorders and symptoms of mental disorders: a systematic review and meta-analysis. Lancet Psychiatry. 2019;6(12):995-1010. Available from: https://doi.org/10.1016/s2215-0366(19)30401-8
Bonaccorso S, Ricciardi A, Zangani C, Chiappini S, Schifano F. Cannabidiol (CBD) use in psychiatric disorders: a systematic review. Neurotoxicology. 2019;74:282-98. Available from: https://doi.org/10.1016/j.neuro.2019.08.002
Allan GM, Finley CR, Ton J, Perry D, Ramji J, Crawford K, et al. Systematic review of systematic reviews for medical cannabinoids: pain, nausea and vomiting, spasticity, and harms. Can Fam Physician. 2018;64(2):e78-e94.