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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.
helen - again !