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Does drug abuse affect memory?

Can the habitual use of illicit drugs damage our memory system? Scientific studies suggest there is a link but more research is needed in this complicated contentious area.

Everything we do changes our brain in some way. The very act of reading this sentence will (very) subtly alter your brain chemistry. However, drugs of abuse such as cocaine, cannabis and ecstasy set off a much more powerful cascade of changes that can have severe consequences for the user, consequences that may include memory loss.

Drugs and the brain

It is remarkable when you consider that the different active ingredients in psycho-active substances are nearly identical in structure to the brain's neurotransmitters. Neurotransmitters are the brain's chemical messengers and help to pass information between brain cells. A common neurotransmitter is dopamine, which amongst other things, activates feelings of pleasure. When our brains release dopamine, it feels pleasurable and then natural processes mop-up excess dopamine, bringing our pleasurable feelings to their natural end. But this is not the case when we introduce a drug like cocaine.

Neurotransmitters are designed to attach themselves only to specific receptors in order to pass on information. But the molecules of the active ingredients in cocaine so closely resemble the natural neurotransmitter dopamine that they too can bind to the same receptors. The result is an intense rush of pleasure but more importantly, the molecules of cocaine have also blocked the brain's natural 'mopping-up' mechanism. This helps to maintain the feelings of pleasure for much longer but has a downside to it - addiction. The brain becomes less sensitive to dopamine, in effect requiring more of it to give us the same level of pleasure and addiction is the consequence of trying to feed that ever decreasing sensitivity.


Before looking at the general direction of research data, it's worth remembering that two legal drugs of abuse, nicotine and alcohol have already been clinically proven to cause memory loss. Alcoholism can lead to brain cell death, short-term memory 'blackouts' and something called 'Korsakoff's Syndrome' which is a form of severe amnesia. Smoking is a cause of stroke which can cause short-term memory loss and can trigger dementia.

For illicit drugs of abuse, the picture is less clear but the majority of studies do tend to conclude that long-term drug use affects memory. More than 200 studies have looked at cannabis, a similar number studied cocaine, and over a hundred looked at MDMA (ecstasy). All of this appears hard to argue with but as pointed out by a number of researchers - it's not quite as straightforward as it seems. For example, a 2006 study on memory and cannabis by Riedel and Davies of the University of Aberdeen (2006) states that "care needs to be exercised since many human studies are flawed by multiple drug abuse, small sample sizes, sample selection and sensitivity of psychological tests for subtle differences". In short, there are lots of variables which could unduly influence the results of a study and skew the result. Also, more research is urgently needed into the effects of mild or recreational use of many drugs on memory since that is more likely to impact on a larger section of the population. Few if any research papers have covered all the bases which is why their conclusions are often cautious.

What about drugs to improve memory?

Most of us know a few cups of coffee will keep you going through the night if you're up against a deadline. Mild stimulants can help us concentrate which in turn might also improve our learning abilities. But could a pill really ever improve our memories? Our ability to recall something? It's a topic of serious research and has major implications for the treatment of dementia as well.

Professor Stephen Rose of the Open University has spent a lifetime studying memory and so far, he's pretty sceptical of many claims about memory enhancers: "the idea of memory-boosting pills is appealing". "But," he asks "should we resist the claim that there is automatically a chemical fix for all our psychological fallings?."

Rose recently reviewed the evidence for claims that certain substances can improve memory. What he found, after examining over 100 studies, some on animals, some on people with dementia and some on healthy people, was that most experiments were too poorly controlled to make the claims stand up. Much of what we're told about memory-enhances substances is either "misleading" or "extravagantly over-interpreted" said Rose. Furthermore, he pointed out that most people would expect a pill to help them with recollection, rather than learning, which is what most of the studies focused on. Click to read the full account of Rose's findings.


claire gray
I have anti depressants for the treatment of depression and have been on them for years. Sometimes, I can forget I have done something or forget a simple thing. Some days are worse than others. Not sure if this is caused by the medication or that Im just a dreamer. But recreational drugs to mash your brain up, causing disorders such as Korsakoff's. Not sure if I have spelt it correctly..

I smoked cannabis daily fo fifteen years and it affected all aspects of my life, mostly in a detrimental way. My ability to remember even the simplest of things was seriously impaired and lack of motivation was another problem. Since virtually cutting it out completely, my thirst for knowledge and memory has returned as has my social life!

drugs have mushed up my brain, my ability to remember things now is unbelievable, sometimes ill say something then just after i've spoken it i'll forget or think "did i just say that, maybe i just thought it" i think lowering the class for cannabis was a joke, i've coutless friends who are a mess now from it, they dont do anything all day, no motivation, no wonder the countrys a a strong beliver in drugs are illegal for a reason now....

I too have partaken of various illicit substances over the years, including Cannabis, LSD, and Speed. I have cut back on my intake of these substances and have found that my memory is as sharp today as ever it was - I'm 43 by the way. I hope this puts your minds at rest - memory can return, you just need to exercise it.

helen - again !
regarding the cannabis use of my ex, I have since found out that over the past year he has also been using ecstasy and speed. He snaps at people, including his closest friends when they challenge his behviour. He continually makes excuses not to do things, like find a better job or some decent living accomodation. Both myself and his friends are now wondering if he makes excuses because he knows he won`t remember what he said. I`m not sure what this contribution may have to do with your memory page really. I suppose it could act as a warning to others. The saddest part is that his children don`t like his behaviour, he irritates them. He obviously has some serious issues related around his mental health, memory, well being etc. This has to be exacerbated by his drug use.

I have smoked cannabis almost daily for about 4 years now, since I was 18. I just took the memory test on this site and I thought I did pretty well. I acknowledge that smoking marijuana has an effect on the way my brain operates (obviously, that's why I do it) but I do not seriously believe that it has (yet) had any strong effect on my memory, either short or long-term. I used to forget things a fair bit anyway (before I smoked) and I wouldn't say that I forget things more now. If anything, because I am aware that people claim smoking weed causes memory loss, I have paid close attention to my abilities of recall and tried to ensure that I focus and excersise my memory. If there's something I can't remember that I know I should, I will concentrate until I find it and, only occasionally do I have to look the information up. From another perspective, smoking weed has prompted me to research into all kinds of areas of knowledge that I might not have done (more motivated and curious when stoned) so it is entirely possible that my memory is being used more thoroughly now than before.

Im 18 years of age and for 3months straight, beginning May 2005, I smoked weed quite frequently, bordering on non-stop, and my ability to remember things was...abysmal and I found myself in a perpetual state of unawareness which was terribly unlike me as I was used to having the memory of an elephant and being recognized as quite "intelligent". I feel I currently suffer from a bad memory among other things, however my memory operates better when I am focused on a task or in a good mood. When I am depressed or feeling lethargic, granted, it doesn't work so well. And I like many others have said before me am almost certain I haven't fully recovered my keen memory which I most definately have/had.

my ex has been smoking cigarettes and cannabis since the age of 10, he is now 53. He finds it hard to remember things that were said to him 10 minutes ago and cannot recall conversations from the previous week. I used to think, and still do,that he deliberatly forgot things he was asked to do around the house because he was too lazy to do anything.I also think he has a `selective memory` in that he will do the things that please him or do things for his friends but not his family. He also suffers from bouts of depression. I am so convinced that his long term cannabis use has affected his memory .

I have the same experience as Minx: my memory works fine during the day and after smoking I have the memory of a goldfish. I don't think smoking cannabis in moderation has long-term effects on memory. Memory ability declines with age anyway, so when people say their memory has never recovered after smoking then how do you know it was the smoking that caused it?!

I have had exactly the same experience – after smoking cannabis socially, I have difficulties recalling details. It’s a shame it weren’t advertised as harmful as much as other ‘Harder Drugs’ – but I’m fully responsible for my own actions :-( Now i've been Weed-Free for 6 months, but im convinced i still havn't recoverd from the memory dilemma!!

Well I can agree if you were stoned at work. I remember hundreds of phone numbers and account numbers at work. Have smoked cannabis for 7 years now and still have a sharp memory during the day. Once I start smoking however I can't remember anything! Quite nice to forget for a while tho!

Susie Flux
I was on chemotherapy (FEC) for breast cancer and think my memory went rather hazy. Kylie Minogue mentioned this in her recent interview. I wonder if this is a common occurance. My memory seems to have gone back to normal - I think!

When I was around 19 years old I work in a garage. One of my jobs was to order parts for the workshop. I could remember over 30 telephone numbers of all the various suppliers and what they sold and many part numbers. Unfortunately I got involved in smoking cannabis quite heavily and after about 3 months I couldn't remember that last number I dialled. I am not sure if I have now recovered my full memory capability!!



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