In the study, using the drug continuously for three months increased Alzheimer's risk by 51 percent. (Representational Image)klesta/Flickr

Prolonged use of certain psychoactive drugs can cause irreversible damages to the brain, researchers warn.

A study conducted on about 9,000 people living in Quebec, a province in the east- central Canada has found a direct link between benzodiazepines, a drug used to treat insomnia-anxiety and Alzheimer's disease, a brain disorder that leads to the destruction of memory and other important functions of the brain. It is one of the most common causes of dementia.

Dementia is a syndrome related to the brain that leads to memory loss, difficulty in communicating, thinking, understanding, planning and the ability to perform daily routines. Nearly 44 million people across the globe are estimated to be living with dementia and the number is expected to be more than triple (135 million) in 2050.

Benzodiazepines, according to addictioncareclinic.com, contain "hypnotic, anxiolytic, anticonvulsant, amnestic and muscle relaxant" properties that work by activating GABA receptor GABAA that puts a hold on the "higher neuron activity."

Researchers from Canada and France used the Quebec health insurance program database (RAMQ) to identify people who used benzodiazepines. During the first six years of the study, nearly 1,796 people developed Alzheimer's.

In the study, using the drug continuously for three months increased Alzheimer's risk by 51%. The risk went up with an increase in the total time one used the medication. Similarly, people who used long-acting benzodiazepines had higher Alzheimer's risk than those who used short-acting drugs.

Concerned with the findings, researchers urged patients to avoid using the medications for a long time.

"Benzodiazepine use is associated with an increased risk of Alzheimer's disease," the authors wrote, while concluding their study. "Unwarranted long term use of these drugs should be considered as a public health concern."

The study couldn't underline the factors that led to this occurrence, but experts suspected various factors including the health conditions themselves, rather than the medications playing a huge role.

"This study shows an apparent link between the use of benzodiazepines and Alzheimer's disease although it's hard to know the underlying reason behind the link," Dr Eric Karran, Director of Research at Alzheimer's Research UK, said in a statement appeared on the website. "One limitation of this study is that benzodiazepines treat symptoms such as anxiety and sleep disturbance, which may also be early indicators of Alzheimer's disease."

"These drugs would have been given to treat symptoms and it is possible that the latter may have been the earliest signs of unrecognised Alzheimer's disease, although the authors have tried to control for this as far as was possible in their study," Prof Gordon Wilcock, Emeritus Professor of Geratology at the University of Oxford, told The Telegraph.

The study has been published in BMJ on Tuesday.