The interest in senile disease is rising gradually because aging society has become a more common phenomenon. Types of dementia include AD, vascular dementia, paralytic dementia, Lewy body dementia, carbon monoxide induced dementia, and trauma dementia [1,2]. The onset of AD has continued to increase since 1995, while the prevalence of vascular dementia is gradually decreasing. Therefore, AD draws attention from researchers [3]. AD is a disease that is caused by the gradual degeneration and death of cerebral cortical cells. The main symptoms are memory loss, cognitive decline and behavioral disorders [4]. Histopathologically, overall encephalatrophy, senile plaques, and neurofibromatosis (NFT) are the common characteristics of AD [5]. Acquired cognitive deficits caused by AD have a significant impact on the social life and activity of the patients [6]. Moreover, active treatment of memory disorders greatly affects the prognosis of AD patients [3]. Consequently, many researchers acknowledge the need for a therapeutic drug to restore the memory and cognitive damages of AD patients, and various studies have been conducted.

There are three Cannabis species: C. sativa, C. indica, and C. ruderalis [7]. Cannabidiol (CBD), which is attracting attention as medical cannabis, belongs to cannabinoids [8]. Cacao, the main ingredients of chocolate, and the caryophyllene of black pepper also belong to cannabinoids [9].

Cannabis contains at least 113 kinds of cannabinoids. THC (Δ-tetrahydrocannabidiol), CBD, CBG (Cannabigerol), and CBN (Cannabinol) are well-known cannabinoids and many studies have been conducted on them. [10] using rats have shown that THC killed cancer cells and reduced tumor size. It has been reported that CBG expands blood vessels and protects the nervous system [11]. Since CBN is effective for inflammation, pain control, and insomnia, patches containing CBN ingredients are commercially available for human use [12]. Despite these advantageous effects, its use is currently restricted in South Korea according to the Narcotics Control Act (Law No. 15939) in order to prevent health hazards due to drug abuse. However, cannabis is legally used for medical or recreational purposes in several states of the US [13]. Although the medical efficacy and effects of cannabis have been actively studied, cannabis research is quite lacking in South Korea. Therefore, the objective of this study was to discuss the research trend of dementia treatment using cannabis for the purpose of providing the basis of cannabis use for medical purposes in the future.

The number of patients with dementia has been increasing gradually and it is predicted that it will reach 81.1 million in 2040 [23]. It is also forecasted that the number of patients with dementia will be 800,000 in South Korea in 2020 [24]. Additionally, the Ministry of Health and Welfare estimates that about 10% of the population aged 65 or older will suffer from dementia in 2025 and it will cost 30 trillion KRW to treat them [25]. However, we yet do not have a solid treatment to cure dementia and the current standard medications mainly focus only on delaying dementia and recovering symptoms [26].

Therefore, we conducted this study to provide a basis for the treatment of dementia using cannabis, which is currently illegal in South Korea but known to be effective against neuroinflammation, while an effective method is needed for treating dementia, which is gradually becoming a social problem.

This study conducted P&I cross-search targeting publications published or registered to databases by Aug 22, 2019, using the full-text and abstracts of publications. Finally, nine studies [14–22] were selected and analyzed.

The results of these studies confirmed that CBD activated the peroxisome proliferator-activated receptor-γ(PPARγ) through the Wnt/β-catenin pathway to protect PC12 cells from Aβ neurotoxicity and oxidation stress, increase cell survival, reduce ROS production, reduce lipid peroxidation, inhibit the hyperphosphirylation of tau protein, inhibit AChE, and stimulate the neurogenesis of the hippocampus.

Additionally, CBD+THC treatment to AβPP/PS1 transgenic mice revealed that CBD+THC treatment was effective in memory and CBD+THC treatment was more effective than CBD alone or THC alone treatment. These results implied that the CBD components of cannabis might be useful to treat and prevent AD because CBD components could suppress the main causal factors of AD. Moreover, it was suggested that using CBD and THC together could be more useful than using CBD or THC alone.

We hope that there will be a solid foundation to use cannabis for medical use by continuously evaluating the possibility of using cannabis for clinical purposes as a dementia treatment substance and cannabis can be used as a positive tool.