More long-winded pedantry about drugs - Tactical Ninja
Apr. 3rd, 2013
10:34 am - More long-winded pedantry about drugs
You might remember that last week the lecturer for the course I was so critical of sent me some references so I could check for myself. Last week I looked at the statement that 500,000 users of heroin in the US in the early 1970s was reduced to 200,000 by 1974, and that this was due to the influence of this dude. While I couldn't find evidence to support that exact figure and discovered that exact figures on this are pretty much impossible to produce, I did find support for the idea that the number of heroin users dropped significantly in the early 1970s. I also found a number of reasons for that drop, the most likely being the cessation of the Vietnam War meaning that addicted soldiers were no longer being introduced to the population at a high rate, a swing to a preference for other drugs in the population (mostly cocaine from what I gathered), a shortage of heroin due to policies implemented in the Middle East and Asia, and targeted interventions such as the methadone program. I am less sure about the Maharishi, as I couldn't find anything at all about that.
However, the reference supplied by the lecturer on a reduction in the number of heroin users was supported in principle, if not in direct evidence. That's good enough for me to accept the first part of that argument.
The other set of refs he sent me were related to research into the effects of long term heroin use on the brain. The lecture slide claimed that long term drug use damages the brain, and I had asked for references, mostly because of the generalisation of 'drug use', because I know this is not the case for all drugs. However, I was personally unclear on whether heroin was a culprit or not, so I read the references. Now my brain hurts. I should write an article on how reading about the neuroscience of addiction damages the brain. *snerk*
The first one was Profiles of Cognitive Dysfunction in Chronic Amphetamine and Heroin Abusers.
This study compared amphetamine users with heroin users and control subjects on a battery of cognitive tests. It found that while both amphetamine users and opiate users were impaired, it was in different ways - the amphetamine users were impaired on extra-dimensional shift tasks, spatial working memory, and pattern recognition memory (associated with temporal lobes). Heroin users were impaired in learning intra-dimensional shifts, spatial working memory, and strategic performance - they struggled to learn how to strategise a test even after training, and tended to repeat behaviours.
They concluded that different drugs may lead to different types of cognitive impairment, that amphetamine seems to be associated mainly with loss of 5-HT from the orbitofrontal cortex, and they mention that their results stand in contrast to previous studies that heroin abusers do not exhibit typical frontal-executive deficits - which implies they think there's a frontal association there too, but it seems unclear.
Dissociable deficits in the decision-making cognition of chronic amphetamine abusers, opiate abusers, patients with focal damage to prefrontal cortex, and tryptophan-depleted normal volunteers: Evidence for monoaminergic mechanisms.
This one compared amphetamine users with opiate users, and also with people with lesions on their prefrontal cortex, and finally people in a tryptophan-depleted state; using a cognitive decision-making test. They found that amphetamine users made suboptimal decisions and made them slowly, whereas opiate users made good decisions but made them slowly. The prefrontally damaged people showed results similar to amphetamine users, and also the lowered tryptophan people.
They associate prefrontal cortex activity with decision making, and conclude that both depleted tryptophan and chronic amphetamine abuse can lead to behaviour consistent with impaired prefrontal cortex function. Opiate use, on the other hand, demonstrates a different type of impairment, and they say this about it:
"Thus, the increased deliberation times shown by both the chronic amphetamine and opiate abusers in our decision-making task is consistent with altered neuromodulation of the circuitry incorporating ventral areas of PFC, ventral striatum, and amygdala, associated with the abuse of these substances. Moreover, the absence of any relationship between this particular impairment and years of abuse suggests that this deficit does not necessarily reflect an enduring or cumulative disruption of this circuitry. Additionally, in the case of opiates, it is possible that chronic abuse may directly alter opioid receptor functions in the PFC itself (Mansour et al. 1988)."
This is interesting. I think it's trying to say that this impairment shown by opiate users is not consistent with cumulative damage to the prefrontal cortex, but instead with the function of the opioid receptors - but I'm finding it a bit hard to interpret that sentence, not being a neuroscientist. Anyway, the study itself focuses mainly on amphetamine and its effects being similar to the other test subjects, with the heroin associations being somewhat less focused-on.
It mentions that further research is needed to ensure that the correlation between the different drugs and associated behaviour patterns is fully understood - that poor decision making may lead to amphetamine abuse, for example, rather than the other way around. This is good to see - so many researchers draw a causal conclusion when it's drugs being researched, and don't even entertain the possibility that it may be more complex. So this makes their study much more credible in my opinion.
You'll note that the first two studies had a bunch of crossover in terms of authors and researchers, and also that these studies involved performing tests designed to measure cognitive function and drawing conclusions from the results. The next study, they actually looked inside (sort of) people's brains.
Brain Disintegration in Heroin Addicts: The Natural Course of the Disease and the Effects of Methadone Treatment. I have to say the title of this one makes me go *gnng*, especially after you read the article and discover that at no point is anyone's brain actually seen to be disintegrating. However, I'll cut them some slack for English not being their first language, and also for going for the shock-value title - I've done that myself. But, it does set it up to appear as if they are firmly in the 'drugs are bad' camp, and brings their objectivity into question.
Anyway, so these researchers used EEG to measure activity in the brains of chronic heroin users and control subjects. They found abnormal electrical activity in the central brain area, starting in the left hemisphere and moving to right hemisphere, correlated to the length of time using heroin. They related this to cognitive function (unspecified) and craving for heroin.
They also found that short term heroin users did not differ from 'normal' people on cognitive tests associated with prefrontal activity, but that individual variations were found in patients who injected a larger amount of heroin immediately before entering the clinic (well duh). Weirdly enough, they used this lack of difference to assume that these people had prefrontal dysfunctions and that caused them to self-administer more heroin, as opposed to perhaps assuming that having just injected heroin might affect one's performance on tests. Hmm..
In terms of long term use, they found that patients with a longer history of heroin use gave a significantly poorer performance on orbito-frontal neuropsychological tasks than 'normal' subjects. They also mentioned in their discussion of 'concomitant brain damage' that a significant number of long-term users had suffered non-fatal overdoses, which can lead to oxygen deprivation in the brain, which can cause injury. These appear to be mostly associated with posterior brain 'disintegration' - I think here they mean lesions, since in the discussion they compare it with types of lesions caused by brain diseases, injury, and age.
Apparently they also found that methadone maintenance patients had more severe cognitive impairment than heroin users.
So what can I conclude from all this? Well, first I'd like to say that due to time constraints, I haven't looked at any other refs than these ones, to see if there is research that comes to different conclusions. However, I think we can be fairly sure that long term heavy heroin use can lead to cognitive impairment that is at least in part consistent with changes to the prefrontal cortex. I would not go so far as to say 'damage' after reading these articles, but there's definitely something going on in there. Also, I couldn't conclude that it was specifically the prefrontal or frontal cortex that appear to be affected - again, not a neuroscientist, but the observed changes in cognition appear to have been spread more widely in the brain. My brief look at alcohol-related impairment seemed to show a similarly wide spread with alcohol - here acknowledging that I haven't researched this in depth.
Now, in the lecture, what I said was that as far as I knew alcohol and methamphetamine were acknowledged culprits for affecting the brains of users, and that I wasn't sure about heroin but I didn't think so. I stand corrected there, obviously, and I'm happy to acknowledge that publicly. I should also point out that in one of those articles up there, there's a discussion of cocaine that points out mild impairments having been demonstrated in long term cocaine users too, but that another article (the ones with the similar authors) says there is no evidence for the neurotoxicity of cocaine - which implies any changes in the brain due to cocaine use have a more complex correlation than simply 'cocaine use causes x'.
Anyway, this whole thing came about because in the lecture, the lecturer's slide simply said (something along the lines of): "Long term drug use damages the brain." And I took exception to that, asking for references to support the statement. The reason for this is that in the field of drug policy, the first thing you learn is that 'drug' is an arbitrary term and that it's extremely unwise to talk about 'drugs' as a monolith. For a start, it causes people to assume one drug is like another, which can be dangerous if you're talking about people assuming that heroin is the same as marijuana (the lecturer did touch on this elsewhere to his credit). Secondly, if you want policy to be based on evidence instead of moralising or assumption or ignorance, you have to be specific about what evidence relates to what drug.
The idea of 'drugs' as the scourge that's destroying our society is an old one, brought into focus by Nixon and his War on Drugs. He didn't differentiate between different drugs, and our drug law and policy is a product of that, complete with a great deal of harmful misinformation and mythology (like the gateway theory or the concepts of 'hard' and 'soft' drugs) that is accepted as true by the majority of people who have grown up immersed in Drug War rhetoric. "Long term drug use damages the brain" is part of that rhetoric. This type of statement is harmful because it reinforces this mythology in people's minds, and causes people to just accept the continuation of policies that have been so harmful in the past, because it's 'common sense'. This makes it very difficult to implement harm reduction policies in the face of the ignorance and knee-jerk reactions of politicians and the voting public. We need specifics and we need evidence, and I care a great deal about making sure these specifics and evidence get to as many people as possible.
So what should that slide have said? Well, I reckon something like "Long term chronic use of certain drugs can cause cognitive impairment." Underneath this in brackets (eg alcohol, amphetamines, heroin). Spoken: Long term heavy use of these drugs has been shown to produce cognitive impairment consistent with changes to the brain, such as.. etc etc etc.. And at the bottom of the page, footnotes linking to the studies.
That's how I'd do it anyway. The lecturer has told me he's changed the slide in question so it no longer makes that broad statement, so credit to him for that. I realise the statement above does not have the same impact, and that the next step of the argument was drawing a relationship between the effects of transcendental meditation on the brain and its potential for use in rehabilitation therapy. But if that's the case, then showing the specifics and producing evidence for how this therapy works to target the specific impairments, all backed up by research and evidence that pedants like me can look up, will make the argument stronger. And if the evidence isn't there, then not making the argument will make the lecture stronger. In my opinion, obviously.
So there you have it. The lecturer produced the refs I asked for, I read them, and learned something about heroin, while he has made an improvement to his lecture series by removing a generalisation. Win/win again. Sweet!