As a human being, the saddest thing is to forget the past, such as family, friendship and love. Memories are buried, memories are devoured, and this is the true picture of Alzheimer's disease.

According to the World Health Organisation, about 47 million patients are suffering from Alzheimer's Disease, with a gradual loss of memory function in the brain, from a small portion of memory at the beginning, to a large portion of memory, to all memory, to the point that in the end, they cannot take care of themselves at all, and their body's functions are also gradually weakened.

Today, 21 September, is the 30th World Alzheimer's Day. Available data show that the prevalence of dementia in the elderly population aged 60 years and above is about 6.19 per cent, of which about two thirds are caused by Alzheimer's disease, with the main pathological changes being the formation of senile plaques by β-amyloid deposition and neuronal fibrillary tangles formed by the abnormal aggregation of tau proteins.

The most common age of onset of Alzheimer's disease (AD) is 65 and over, and its prevalence increases with age, with 5 per cent of people aged 65 to 74 having Alzheimer's disease, 13.1 per cent of people aged 75 to 84, and an even higher prevalence of 33.3 per cent of people aged 85 or over.

There is no cure for Alzheimer's disease, and there are no treatments proven to slow its progression. However, doctors often prescribe several medications that may help improve mental functioning in people with Alzheimer's disease, such as donepezil and tacrine.

Recent studies have shown that medical marijuana for Alzheimer's disease can prevent the formation of brain deposits associated with the degenerative disease. They have also found that medical marijuana is one of the most effective medications for Alzheimer's disease.

In July 2014, another study published in the Journal of Alzheimer's Disease investigated whether THC (tetrahydrocannabinol) could slow or stop the well-known symptoms of AD.

In 2016, scientists at the Salk Institute announced that cannabinoids may be neuroprotective against Alzheimer's symptoms by affecting inflammation and amyloid beta accumulation in nerve cells.

Here are five ways cannabis can help treat cognitive decline in Alzheimer's disease:

1. THC is a psychoactive compound found in certain cannabis strains. Multiple studies have examined the effects of THC on neuritic plaques, and THC has been shown to slow the formation of destructive plaques in the brain.

Small doses of THC slow the growth of beta-amyloid, the protein responsible for producing neuritic plaques. In fact, one study showed that the amount of THC in medical marijuana had a greater ability to stimulate neuritic plaque removal compared to the Alzheimer's drugs Aricept and Connexion.

2. Cannabis also contains another plant compound called cannabidiol (CBD) . Unlike THC, which produces psychoactive and mind-altering effects, CBD offers other health benefits that can help treat Alzheimer's disease.

CBD has natural anti-inflammatory, antioxidant, analgesic and sedative effects.Neurological studies of CBD have shown that it can help slow down the process of cell death called apoptosis. In combination with THC, it shows promise in reducing oxidative damage, inflammatory events and other mechanisms that contribute to brain degeneration. This means that CBD could help people with Alzheimer's disease by stopping healthy brain cells from dying.

3. A major factor in the development of Alzheimer's disease is the inflammation surrounding the plaque that builds up in the brain. Cannabinoids have shown promise in reducing inflammation and slowing cognitive deterioration. Animal tests have shown that medical marijuana can help reduce inflammation around neuritic plaques.

4. Cannabinoids help to stimulate the growth of tissue in the part of the brain that controls memory, called the hippocampus. For people with Alzheimer's disease, this means that medical marijuana can help improve memory function by stimulating a higher rate of neuronal growth.

5. People with Alzheimer's disease often suffer from a wide range of symptoms. Medical cannabis has also shown the ability to help improve the quality of life of people with Alzheimer's disease by reducing and controlling many of these symptoms.