In a paper recently published in the journal Drug and Alcohol Dependence, Danish researchers attempted to establish standard mortality ratios for the drugs cannabis, cocaine, amphetamine, MDMA (ecstasy) and opioids (e.g. heroin)*, while taking into consideration the effects of two intervening variables: drug injection with needles and psychiatric disorders (Is the mortality rate of cocaine users mediated by whether they have, for example, clinical depression?)
(*Individuals’ primary drug of choice)
The population they looked at included 20,581 people treated for drug abuse in Denmark over a 10-year period from 1996-2006. (These data are correlational and, therefore, the possibility of unidentified moderating variables exerting an effect on death rates is high.)
In brief, the results showed the following:
1. Those who injected drugs showed significantly higher mortality rates across the board. (This does conflict with past findings, which found no difference.)
2. Overall, psychiatric illness was not associated with higher mortality rates, with the exception of cocaine/amphetamine users, who, if they presented with psychiatric disorders, did show higher morality rates.
3. Pot smokers showed 5x increase in mortality rates (compared to the general population). Researchers suggest that increased mortality among pot smokers could be related to driving accidents, violent injuries and various other types of accidents. (a personal note: Based on my personal experience, this seems unlikely. Pot smokers tend to drive very conservatively (too slow, if anything!) and are famously not prone to violence.) What seems more likely to explain pot smokers’ higher mortality rate is that they are also using other drugs. Other studies have borne this out.
4. Cocaine and amphetamine users showed 6x death rates of the general population. Previous reports on stimulant abuse related deaths are highly variable. The variability is likely the result of other factors including physical conditions, HIV/AIDS, overdose, cardiovascular problems, injuries accidents, violent deaths and suicides.
5. Opiod users show increased mortality rates. Findings for both stimulants and opioids are in accordance with studies from other countries. Users of Heroin and other opioids showed by far the highest mortality rates of all drugs of abuse.
6. Ecstasy (MDMA) users did not show increased mortality rates. (However, it’s possible that a low number of deaths from MDMA contribute to low statistical power).
Conclusions that can be drawn from this report? Stay away from all drugs if you want to increase your chances of staying alive; but, especially, don’t do intravenous heroin. Psychiatric disorders plus drugs of abuse aren’t associated with increased mortality risks except for in the case of cocaine/amphetamine. Ecstasy is unlikely to kill you on its own, but that’s not to say it won’t do some long-term damage if abused. Although marijuana users showed higher mortality rates, there’s not good reason to believe this is solely the effect of marijuana, but other factors. Finally, the population under study here consisted of people seeking treatment, so it’s unknown if this represents the drug using population as a whole.
I think it’s pretty clear, given the number of questions and unknowns this study presents, that there is a lot more to learn about drug-related mortality risk.
Arendt M, Munk-Jørgensen P, Sher L, & Jensen SO (2011). Mortality among individuals with cannabis, cocaine, amphetamine, MDMA, and opioid use disorders: a nationwide follow-up study of Danish substance users in treatment. Drug and alcohol dependence, 114 (2-3), 134-9 PMID: 20971585
Research has shown that people’s names influence what professions they choose to enter; for example, men named Dennis are overrepresented among dentists and men named Raymond are overrepresented among doctors who specialize in radiology.
I wonder if guilt about his name is what drove the third author below to study the ill effects of cigarette smoking …
A couple of nights back, I attended a panel discussion at Rockefeller University in NYC, organized by SONYC and sponsored by Nature. Entitled Courting Controversy : how to successfully engage an online audience with complex or controversial topics, The meeting consisted of a three person panel, a climate scientist, a pediatric clinician and a former science journalist, addressing a crowd full of journalists and scientists. I won’t give a full review but just a couple of quick points.
One question that emerged from the meeting was whether or not the role of scientist bloggers and/or science journalists should be to educate their readers. The consensus that emerged from the panel seemed to be that education should not be a goal. One panelist, Gavin Schmidt, a climate researcher at NASA’s Goddard Institute for Space Studies and a driving force behind the RealClimate blog, made mention of how scientists live in the space between the known and the unknown, and that in order to really understand discoveries that emerge from this space in a given field, one would need an extensive background education, e.g. the kind of background that one receives when doing a PhD. This kind of education, Schmidt said takes many thousands of hours and can’t very well be accomplished through reading blogs or articles in mainstream media.
While this is certainly true, I’m not sure that science writers are not educating their readers. It’s perhaps a question of how you define “educate”. It might be defined as an act by which one is, “qualified or trained for a particular calling, practice, or trade.” By that definition, any given piece of science writing would certainly not qualify. But, education can also be defined, more simply, as the act of providing something of informational value. Science writers certainly do that. And to the extent that a person’s opinion is influenced by information they’ve consumed, whatever the format, then I think we can say some educating has taken place.
One other point that stuck with me was made by David Ropeik, a former journalist who runs the blog, On Risk. He made the point that negative messages carry much more weight than positive messages. Not a new observation, to be sure, but it’s good to be reminded that to participate in the news/information space is to be in competition for reader’s eyeballs. How one frames their message is probably as important as the message itself. The “competition” probably has less scruples than you. Negative sells. One ignores this maxim at their own peril.
There was some good vigorous discussion in the latter part of the event and the whole thing should be online soon.
The ability to dance to music comes naturally to most members of the human species, and even exists in some species of bird, most famously a cockatoo and YouTube celebrity named Snowball.
But it doesn’t come naturally to everyone.
Researchers from McGill University and the University of Montreal (Phillips-Silver, 2011) have recently published a case study of a student named Matthieu, who not only can’t dance to the beat, but also can’t tell when someone else is dancing asyncronously, although he can dance in time if he is able to watch someone else doing it.
“Mathieu was discovered through a recruitment of subjects
who felt they could not keep the beat in music, such as in clapping
in time at a concert or dancing in a club. Mathieu was the
only clear-cut case among volunteers who reported these problems.
Despite a lifelong love of music and dancing, and musical
training including lessons over several years in various instruments,
voice, dance and choreography, Mathieu complained that
he was unable to find the beat in music. Participation in music
and dance activities, while pleasurable, had been difficult for
Experimenters put Matthieu and a group of control subjects through a series of tests in which they danced to various types of music. Measurements were gathered by way of a Wii controller (which contains a accelerometer) that was strapped to the trunk of each subject’s body and was able to track and quantify their movements. They also had participants tap their hands to the beat, while not dancing. Finally, they watched videos of someone else dancing (increasingly out of sync) to some Merengue music, and were to asked to identify if the person dancing in the videos was in sync with the music or not.
Matthieu couldn’t tap a beat in time and the style of music didn’t seem to matter; across numerous styles of music, he couldn’t dance in sync with the groove.*
*He was able to sync himself somewhat to a techno beat, which is basically a glorified metronome but nonetheless slightly more complex.
However, he had no problem locking his movements to the beat of a metronome and could bounce with a consistent tempo without music, while showing normal levels of pitch and tonal perception. He demonstrated normal intelligence, presented no history of neurological or psychiatric disorders and showed so signs of obvious cognitive deficits. It seems Matthieu’s deficit is specific to perceiving the underlying pulse in a piece of music and moving his body to it. In other words, he’s got beat (rhythm) deafness.
Scientists have been aware of the condition for quite a while.
In an Australian Medical Journal from 1890, a surgeon from the Victorian Eye and Ear Hospital in Melbourne described a case of rhythm deafness in a 27-yr. old farmer named W.M.:
(Unlike Matthieu, the farmer’s deficit was much less selective; he also suffered from tone deafness and had severely reduced pain sensitivity)
More recently, Oliver Sacks touched upon rhythm blindness in his book Musiciophilia:
Google and PubMed searches find numerous casual references to “rhythm deafness”, but this does seem to be the first well documented case in the scientific literature. So, if its been talked about for so long but documented so infrequently, how rare is it?
Lead author Jessica Phillips-Silver suggested that it might be as rare as tone deafness, which affects about 4 to 5% of the population. If that’s the case, it could be a real challenge locating enough participants to conduct an fMRI study, which would help reveal the neural regions implicated in the condition. But the research team is confident, in part due to ample press coverage of the paper, that they’ll find more subjects.
So, what might an fMRI study reveal about the condition?
A 2005 study (Brown) examining the neural substrates of dance points to one possibility. In this study, subjects lay in a PET scanner and danced a tango with their legs only, both accompanied by music and free form (without music).
Participants in the dancing-to-music condition showed BOLD activation suggesting that audio-motor entrainment might be mediated through a connection between subcortical auditory areas and the cerebellum. This would make sense give that one of the primary functions of the cerebellum is to coordinate motor actions, particularly precision and accurate timing, by receiving input from the sensory system and integrating those incoming signals to execute fine tuned motor activity.
The authors suggest that the deficit might be primarily perceptual and point to the fact that he failed on a task which did not require body movement, nor does not have any basic motor impairments They also suggest that basal ganglia connections between auditory and motor cortices could play a role, particularly the dorsal auditory pathway leading to the dorsal premotor cortex. Silver and colleagues already have some neuroimaging work underway with Matthieu.
As for future directions, Silver-Phillips said that her group will be looking at exactly what level of musical complexity is required for Matthieu’s beat deafness to emerge. They’re also interested in exploring whether there is any sign of entrainment occurring on a neuronal level, even in the face of the behavioral deficit. In other words, maybe his neurons are dancing to the beat even if he’s not.
Phillips-Silver J, Toiviainen P, Gosselin N, Piché O, Nozaradan S, Palmer C, & Peretz I (2011). Born to dance but beat deaf: A new form of congenital amusia. Neuropsychologia, 49 (5), 961-9 PMID: 21316375
Brown, S. (2005). The Neural Basis of Human Dance Cerebral Cortex, 16 (8), 1157-1167 DOI: 10.1093/cercor/bhj057
It’s one of the truisms of human life that teenagers often do silly, stupid and/or dangerous things. We certainly don’t need science to tell us that. One reason this seems to be the case is that, on average, teens have trouble optimally weighing risk vs. reward. I’m not excluding myself from this characterization. In fact, I sometimes marvel that I survived my teen years intact, if at all.
One stupid thing I and many of my friends did as teenagers was to try smoking.
There are no rational arguments in favor of smoking. Yet, according to one study, most adult smokers start before age 19 and 70% of all adolescents report trying a cigarette at least once. Messages directed to adolescents and teens against smoking often fall on deaf ears. In addition to subpar decision making skills, many teens hold the advice of their elders in low regard and are apt to pick up a cigarette as an act of defiance or as a show of their burgeoning adulthood. Hollywood films certainly contribute to the smoking mythology through their noble portrayals of troubled, rebellious or misunderstood teens reaching for smokes when the chips are down.
Although the health risks associated with smoking are widely known, a recent Nature Neuroscience study has provided even more reasons for teens to avoid smoking. Researchers from the Netherlands found that in adolescent rats, exposure to smoking led to increased and long lasting impulsiveness and impaired measures of attention in adulthood. In contrast, adult animals exposed to similar levels of nicotine did not show these long term effects. So, the impulsiveness that might lead a teen to try smoking could be increased by the very product of that impulsiveness, creating a vicious feedback cycle. Nasty business.
What’s the molecular mechanism? A proteomic analysis of 297 different mPFC proteins in adolescent rats who had exposure to smoking showed that levels of mGLuR2 was downregulated. mGluR2 is a metabotropic glutamatergic receptor that sits on the presynaptic side of synapses in the mPFC, a brain region important for cognitive control and attention. Adolescent nicotine exposure resulted in decreased mGLuR2 signaling and reduced plasticity in the mPFC. This was shown to be directly related to attentional deficits by a rescue experiment in which a glutamate agonist was injected into the mPFC in vivo. The agonist restored attentional performance to normal levels but didn’t affect impulsiveness.
In sum, the adolescent brain is more susceptible to the consequences of smoking via alteration of synaptic mGluR2 protein levels. It’s known that nicotine exerts its initial effects on the brain through nicotinic acetylcholine receptor activation and this study suggests that adolescents are uniquely vulnerable to increased activation of these receptors.
The researchers acknowledge that the sequence of molecular events is unknown, but speculate that “…mGluR2 levels following nicotine exposure at the end of adolescence compensate for nicotine’s actions and inhibit neurotransmitter release.” One caveat to keep in mind is that it’s unknown the extent to which this effect would be replicated in humans. Another important point is that in this experiment, nicotine was dissolved in solution and administered subcutaneously. Cigarettes contain many other carcinogens and toxins to which adolescents could be particularly vulnerable, so the long-term cognitive effects of cigarette smoking could extend far beyond those uncovered in this study, which looked just at nicotine.
The takeaway message is definitely clear: Parents, do everything you can to keep your kids from smoking!*
*I’m an advocate for making the sale of tobacco and tobacco related products illegal. Tobacco offers no clear benefits to society, with the exception of a few thousand jobs and the enrichment of a couple handfuls of business executives, while incurring great economic costs to the nation as a whole. Although nicotine has shown some cognitive benefits to individuals in certain disease states, all in all its mostly detrimental. (I’m a member of that most annoyingly vociferous group of anti-smoking activists: ex-smokers. Maybe we’re so adamant because we know how hard it is to quit!) That long-term cognitive deficits are now being shown to accrue in cigarette smoking teens is hopefully another nail in the coffin of the tobacco industry and smoking culture in general, which will perhaps be looked back upon as a sign of the special ignorance of our times.
Counotte DS, Goriounova NA, Li KW, Loos M, van der Schors RC, Schetters D, Schoffelmeer AN, Smit AB, Mansvelder HD, Pattij T, & Spijker S (2011). Lasting synaptic changes underlie attention deficits caused by nicotine exposure during adolescence. Nature neuroscience, 14 (4), 417-9 PMID: 21336271