March 5, 2014
Virginia Hughes has a nice piece out on generational transmission of……experiences. In this case she focuses on a paper by Dias and Ressler (2014) showing that if you do fear conditioning to a novel odor in mice, the next two generations of offspring of these mice retain sensitivity to that odor.
This led me to mention that there is a story in substance abuse that has been presented at meetings in the past couple of years that is fascinating. Poking around I found out that the group of Yasmin Hurd (this Yasmin Hurd, yes) has a new paper out. I’ve been eagerly awaiting this story, to say the least.
Szutorisz H, Dinieri JA, Sweet E, Egervari G, Michaelides M, Carter JM, Ren Y, Miller ML, Blitzer RD, Hurd YL. Parental THC Exposure Leads to Compulsive Heroin-Seeking and Altered Striatal Synaptic Plasticity in the Subsequent Generation.Neuropsychopharmacology. 2014 Jan 2. doi: 10.1038/npp.2013.352. [Epub ahead of print] [PubMed, Neuropsychopharmacology]
This study was conducted with Long-Evans rats. The first step was to expose both male and female rats, during adolescence, to Δ9tetrahydrocannabinol (THC) at a dose of 1.5 mg/kg, i.p. every third day from Post Natal Day 28-49. No detectable THC was still present in the animals 16 (and 28) days later. The animals were bred at PND 64-68. Parallel Vehicle exposed rats were the comparison.
The resulting pups were fostered out to surrogate mothers in new “litters” consisting of approximately equal male/female pubs and an equal number from the THC-exposed and Vehicle-exposed parents. So this rules out any effects the adolescent THC might have on parenting behavior (that would affect the pups) and mutes any effect of littermates who are offspring of the experimental or control parents.
The paper shows a number of phenotypes expressed by the offspring of parents exposed to THC in adolescence. I’ve picked the one that is of greatest interest to me to show. Figure 1d from the paper depicts behavioral data for a heroin intravenous self-administration study conducted when the offspring had reached adulthood. As you can see, under Fixed-Ratio 5 (5 presses per drug infusion) the animals with parents who were exposed to THC pressed more for heroin than did the control group. They were equal in presses directed at the inactive lever and exhibited equal locomotor activity during the self-administration session. This latter shows that the drug-lever pressing was not likely due to a generalized activation or other nonspecific effect.
The paper contains some additional work- electrophysiology showing altered Long Term Depression in the dorsal striatum, differential behavior during heroin withdrawal and alterations in glutamate and dopamine-related gene expression. I’ll let you read the details for yourself.
But the implications here are stunning and much more work needs to be completed post-haste.
We’ve known for some time (centuries?) that substance abuse runs in families. The best studied case is perhaps alcoholism. The heritability of alcoholism has been established using human twin studies, family studies in which degree of relatedness is used and adoption studies. Establishing that alcoholism has a heritable component led to attempts to identify genetic variations that might confer increased risk.
The findings of Szutorisz and colleagues throws a new wrinkle into the usual human study designs. It may be possible to identify another factor- parental drug exposure- which explains additional variability in family outcomes. This would probably help to narrow the focus on the genetic variants that are important and also help to identify epigenetic mechanism that change in response to actual drug use.
On the pre-clinical research side…..wow. Is it via the male or female…or is it both? Does the specific developmental window of exposure (this was adolescent) matter? Does the specific drug matter? Is the downstream effect limited to some substances but not others? Is there a general liability for affective disorder being wrought? Does the effect continue off into subsequent generations? Can it be amped up in magnitude for the F2 generation (and onward) if the F0 and F1 generations are both exposed?
I think if this finding holds up it will help to substantially advance understanding of how An Old Family Tradition can become established. As I posted before:
In his classic song the great philosopher and student of addictive disorders, Hank Williams, Jr., blames a traditional source for increasing the probability of developing substance abuse:
….Hank why do you drink?
(Hank) why do you roll smoke?
Why must you live out the songs you wrote?
Stop and think it over
Try and put yourself in my unique position
If I get stoned and sing all night long
It’s a family tradition!
March 4, 2014
A communication to the blog raised an issue that is worth exploring in a little more depth. The questioner wanted to know if I knew why a NIH Program Announcement had disappeared.
The Program Announcement (PA) is the most general of the NIH Funding Opportunity Announcements (FOAs). It is described with these key features:
- Identifies areas of increased priority and/or emphasis on particular funding mechanisms for a specific area of science
- Usually accepted on standard receipt (postmarked) dates on an on-going basis
- Remains active for three years from date of release unless the announcement indicates a specific expiration date or the NIH Institute/Center (I/C) inactivates sooner
In my parlance, the PA means “Hey, we’re interested in seeing some applications on topic X“….and that’s about it. Admittedly, the study section reviewers are supposed to conduct review in accordance with the interests of the PA. Each application has to be submitted under one of the FOAs that are active. Sometimes, this can be as general as the omnibus R01 solicitation. That’s pretty general. It could apply to any R01 submitted to any of the NIH Institutes or Centers (ICs). The PAs can offer a greater degree of topic specificity, of course. I recommend you go to the NIH Guide page and browse around. You should bookmark the current-week page and sign up for email alerts if you haven’t already. (Yes, even grad students should do this.) Sometimes you will find a PA that seems to fit your work exceptionally well and, of course, you should use it. Just don’t expect it to be a whole lot of help.
This brings us to the specific query that was sent to the blog, i.e., why did the PA DA-14-106 go missing, only a week or so after being posted?
Sometimes a PA expires and is either not replaced or you have happened across it in between expiration and re-issue of the next 3-year version. Those are the more-common reasons. I’d never seen one be pulled immediately after posting, however. But the NOT-DA-14-006 tells the tale:
This Notice is to inform the community that NIDA’s “Synthetic Psychoactive Drugs and Strategic Approaches to Counteract Their Deleterious Effects” Funding Opportunity Announcements (FOAs) (PA-14-104, PA-14-105, PA-14-106) have been reposted as PARs, to allow a Special Emphasis Panel to provide peer review of the applications. To make this change, NIDA has withdrawn PA-14-104, PA-14-105, PA-14-106, and has reposted these announcements as PAR-14-106, PAR-14-105, and PAR-14-104.
This brings us to the key difference between the PA and a PAR (or a PAS):
- Special Types
- PAR: A PA with special receipt, referral and/or review considerations, as described in the PAR announcement
- PAS: A PA that includes specific set-aside funds as described in the PAS announcement
Applications submitted under a PA are going to be assigned to the usual Center for Scientific Review (CSR) panels and thrown in with all the other applications. This can mean that the special concerns of the PA do not really influence review. How so? Well, the NIDA has a generic-ish and long-running PA on the “Neuroscience Research on Drug Abuse“. This is really general. So general that several entire study sections of the CSR fit within it. Why bother reviewing in accordance with the PA when basically everything assigned to the section is, vaguely, in this sphere? And even on the more-specific ones (say, Sex-Differences in Drug Abuse or HIV/AIDS in Drug Abuse, that sort of thing) the general interest of the IC fades into the background. The panel is already more-or-less focused on those being important issues. So the Significance evaluation on the part of the reviewers barely budges in response to a PA. I bet many reviewers don’t even bother to check the PA at all.
The PAR means, however, that the IC convenes their own Special Emphasis Panel specifically for that particular funding opportunity. So the review panel can be tailored to the announcement’s goals much in the way that a panel is tailored for a Request for Applications ( RFA) FOA. The panel can have very specific expertise for both the PAR and for the applications that are received and, presumably, have reviewers with a more than average appreciation for the topic of the PAR. There is no existing empaneled population of reviewers to limit choices. There is no distraction from the need to get reviewers who can handle applications that are on topics different from the PAR in question. An SEP brings focus. The mere fact of a SEP also tends to keep the reviewer’s mind on the announcement’s goals. They don’t have to juggle the goals of PA vs PA vs PA as they would in a general CSR panel.
As you know, Dear Reader, I have blogged about both synthetic cannabinoid drugs and the “bath salts” here on this blog now and again. So I can speculate a little bit about what happened here. These classes of recreational drugs hit the attention of regulatory authorities and scientists in the US around about 2009, and certainly by 2010. There have been a modest but growing number of papers published. I have attended several conference symposia themed around these drugs. And yet if you do some judicious searching on RePORTER you will find precious few grants dedicated to these compounds. It it no great leap of faith to figure that various PIs have been submitting grants on these topics and are not getting fundable scores. There are, of course, many possible reasons for this and some may have influenced NIDA’s thinking on this PA/PAR.
It may be the case that NIDA felt that reviewers simply did not know that they wanted to see some applications funded and were consequently not prioritizing the Significance of such applications. Or it may be that NIDA felt that their good PIs who would write competitive grants were not interested in the topics. Either way, a PA would appear to be sufficient encouragement.
The replacement of a PA with a PAR, however, suggests that NIDA has concluded that the problem lies with study section reviewers and that a mere PA was not going to be sufficient* to focus minds.
As one general conclusion from this vignette, the PAR is substantially better than the PA when it comes to enhancing the chances for applications submitted to it. This holds in a case in which there is some doubt that the usual CSR study sections will find the goals to be Significant. The caveat is that when there is no such doubt, the PAR is worse because the applications on the topic will all be in direct competition with each other. The PAR essentially guarantees that some grants on the topic will be funded, but the PA potentially allows more of them to be funded.
It is only “essentially” because the PAR does not come with set-aside funds as does the RFA or the PAS. And I say “potentially” because this depends on their being many highly competitive applications which are distributed across several CSR sections for a PA.
*This is a direct validation of my position that the PA is a rather weak stimulus, btw.
As always when it comes to NIDA specifics, see Disclaimer.
February 25, 2014
Apparently pot CAN kill.
Hartung and colleagues conclude from two Cases:
After exclusion of other causes of death we assume that the young men died from cardiovascular complications evoked by smoking cannabis….The assumption of fatal heart failure in both cases is corroborated by the acute effects of marijuana, including a marked increase in heart rate that may result in cardiac ischemia in susceptible individuals, lesser increases in cardiac output, supine blood pressure and postural hypotension….We assume the deaths of these two young men occurred due to arrhythmias evoked by smoking cannabis; however this assumption does not rule out the presence of predisposing cardiovascular factors.
The ONDCP twitter account just posted a very interesting graph on past-month marijuana use rates in the 12-17 year old adolescent population.
This dovetails very nicely with a factoid being twittered today in the #MTF2013 hashtag which is covering the release of the mid-term data from the Monitoring the Future project.
this actually surprised me. That it was so low.
Of course, one’s first suspicion is that states which are liberal enough to pass medical marijuana laws might have adolescent populations that are more likely to smoke marijuana anyway, i.e., regardless of the medical legalization. Be nice to see a workup on teen marijuana use in these states before and after they legalized medical marijuana.
November 4, 2013
The conditional probability of dependence on a given drug is a question that is of substantial interest to users, parents of users, public policy makers and heath care providers. After all, if people simply stopped using a drug once a problem arises then many of the negative effects could be avoided. There is a fair degree of correlation between meeting diagnostic criteria for dependence and someone failing to stop using a drug despite clear and growing negative consequences. (Indeed this is one of the dependence criteria). Therefore, we must consider dependence to be a target of substantial interest.
It can be difficult to estimate the conditional probability of dependence in humans because we mostly have cross-sectional data to work with. And so we must infer conditional probability from dividing the currently dependent population by some denominator. Depending on what one uses for the denominator, this estimate can vary. Obviously you would like some population that uses the substance but what represents a level of “use” that is relevant? One time ever? Use in the past 12 months? Use in the past 30 days?
A new paper by van der Pol and colleagues uses a prospective design to provide additional data on this question.
The authors recruited 600 frequent cannabis users, aged 18-30, and assessed them for cannabis dependence at start, after 18 months and after 36 months using the:
Composite International Diagnostic Interview (CIDI) version 3.0 (Kessler and Ustun, 2004), and required the presence of three or more of seven symptoms within the 12-month period since the previous interview (without requiring the presence of all symptoms at the same time). It should be noted that the CIDI includes a withdrawal symptom, which is not included in the DSV-IV manual.
The study defined “frequent” use as 3 or more times per week for 12 months or more. This is important to remember when trying to assess the conditional probability. It all depends on what you construe as an at-risk population. Here, I’d say these were already rather confirmed cannabis fans.
The authors were interested in the very first incidence of dependence and so therefore excluded subjects who had ever met criteria, this left 269 subjects at intake (retention in the study left N=216 at 18 mo and N=199 at 36 mo). This is another point of interest to me and affects our estimation. Three or more times per week for 12 months or more and 45% of them had never previously met criteria for dependence. There are two ways to look at this. First, the fact that a lot of similarly screened users had already met criteria for dependence suggest that this remaining population was at high risk, merely waiting for the shoe to drop. Conversely it might be the case that these were the resistant individuals. The ones who were in some way buffered from the development of dependence. Can’t really tell from this design….it would be nice to see similar studies with various levels of prior cannabis use.
There were 73 cases of cannabis dependence of the 199 individuals who were followed all the way to 36 months, representing a conditional probability of transitioning to dependence of 36.7% within 3 years.
Now, of course the authors were interested in far more than the mere probability of meeting dependence criteria. They assessed a number of predictor variables to find differences between the individuals that met criteria and those that did not. Significant variables included living alone, mean number of prior cannabis use disorder symptoms, a continual smoking pattern per episode, using [also] during the daytime, using cannabis to “cope”, child abuse incidents, motor and attentional impulsivity and recent negative life events. For this latter, followup analysis identified major financial crisis and separation from someone important as driving events.
As the authors point out in the discussion, the predictors differ from those identified from a more general population. This makes sense if you consider that the range on numerous variables has been seriously restricted by their catchment criteria. The amount of cannabis exposure, for example, did not predict transition to dependence in this study–perhaps because it was well over the “necessary if not sufficient” threshold. This underlines my theme that the denominator matters a lot to our more colloquial estimates of the risks of dependence on cannabis.
Another issue identified in the discussion was the choice to start at 18 years of age for the captured population. Cannabis use frequently starts much earlier than this and many studies of epidemiology suggest that initiation of drug use in the early teens, mid teens, late teens and early twenties confers substantially different lifetime risk of dependence. “The earlier someone starts using, the more likely to become dependent” is the general findings. The authors cite a study showing that the mean age of meeting cannabis dependence criteria for the first time is 18. This is at least consistent with the fact that 65% of their collected sample had previously met criteria for dependence. No study is perfect or gives us the exact answer we are looking for, of course.
A final note on estimating the conditional probability of dependence in the population that uses cannabis 3 or more times per week for over a year. Of the original sample, 331 had already met dependence criteria and were excluded because the interest here was on the first time dependent. If we ignore those 70 people lost to followup during the study, and add the 73 to the 331 then we end up with 76% of those individuals smoking that much cannabis who have already, or will soon, meet dependence criteria.
van der Pol P, Liebregts N, de Graaf R, Korf DJ, van den Brink W, van Laar M. Predicting the transition from frequent cannabis use to cannabis dependence: A three-year prospective study. Drug Alcohol Depend. 2013 Jul 22. pii: S0376-8716(13)00228-7. doi: 10.1016/j.drugalcdep.2013.06.009. [Epub ahead of print]. [Publisher, PubMed]
October 28, 2013
There was a twitt from Dirk Hansen today
which pointed to Chen and McCarron in Current Psychiatry. This paper seems to be a set of diagnostic and therapy recommendations and contains an example Case Report.
This triggered a bunch of the usual incredulity, in this case from @drogoteca.
those two are but the tip of this person’s denialist iceberg on cannabis hyperemesis. He or she is quite convinced that this cannot be a real outcome of chronic pot smoking.
It can and is.
For grins I thought I’d see if there were any new Case reports and found several I had not seen before.
Hickey and colleagues (2013) report a Case of Cannabis Hyperemesis Syndrome that was treated with haloperidol:
A 34-year-old man well known to our ED arrived with epigastric pain, nausea, and vomiting for 4 days. He had been unable to tolerate anything orally but reported temporary relief only with long hot showers. He came to the ED that night to be admitted because he knew his symptoms would not improve, and he was always admitted in the past when his symptoms were so severe. He denied fevers, chills, diarrhea, hematemesis, melena, or hematochezia.
The patient’s history was significant for similar symptoms every 2 to 3 months for approximately 10 years. He reported daily cannabis use since 1992, with only short intervals of abstinence resulting in complete resolution of his vomiting. He has been admitted to our hospital from the ED 7 times and had multiple unremarkable diagnostic tests including 3 computed tomographic scans, an esophagogastroduodenoscopy, and several specialty consults. He has also been admitted to several other local hospitals for cyclical vomiting. Other than substance abuse, he has no known psychiatric history. A diagnosis of CHS was finally made in 2012, a few months before this ED arrival.
Mohammed and colleagues (2013) reported a Case (which they are at pains to point out is from the Caribbean) that resolved with abstinence.
A 26-year-old Caucasian male presented to our center with a
1-week history of severe colicky epigastric pain heralded by significant nausea for 3 weeks. He had approximately 20 episodes of bilious vomiting daily with numerous bouts of retching. He admitted to smoking 4 “joints” or marijuana cigars every day for the last 2 years, and denied alcohol and tobacco use. He had 4 similar episodes over the last 6 months. During
these admissions, he was rehydrated and abdominal imaging revealed no abnormalities. His ongoing nausea was relieved
by taking hot showers, of which he took up to 15 times per day, sometimes for more than an hour.
The diagnosis of CHS was made and he was counseled on abstinence from marijuana. Though he refused to enter a substance
abuse program, he remained cannabis-free and on follow-up at 1, 3 and 6 months revealed no recurrence in symptomatology.
Enuh and colleagues (2013) report a case from the US.
A 47-year-old African American male with a history of epilepsy and drug addiction presented to the hospital with a seizure complicated by nausea, vomiting, and severe abdominal pain. He was known to be diabetic, hypertensive, and addicted to marijuana for 30 years. He smoked two to three “blunts” (cigar hollowed out and filled with marijuana) most days and occasionally up to eight blunts daily. The drug was last taken on the day of his admission.
He immediately went to the bathroom and remained under a hot shower with the exception of two 15-minute breaks for the rest of the day. He believed that a warm shower could relieve his nausea and vomiting. He stated that it made him feel better than medication. Intravenous ondansetron was of limited benefit. It was difficult to persuade him to exit the shower for the rounds and physical examination. Receiving medication and eating were problems because of this compulsive showering. The same event of entrenching himself in the shower had happened 2 months prior to his hospitalization for a grand mal seizure. Abstinence from marijuana during the hospital stay made the patient’s nausea, vomiting, and obsessive warm showering resolve after 3 days.
Not as satisfying as it could be with respect to the workup and the post-hospitalization followup, of course. But interesting.
Sofka and Lerfald (2013) report a series of four Cases. All had histories of chronic cannabis use, all used hot showers to alleviate symptoms and all had negative GI scans and other clinical workups. One individual was reported to have ceased cannabis use and had remained symptom free. The other three were reported as continuing their cannabis use and continuing to have symptoms. Frustratingly, the authors do not specify the followup duration for any of the cases.
Gessford and colleagues (2012) report a Case that is significant for the comment on the efforts to find a cause prior to the identification of CHS:
A 42-year-old Caucasian female, who has routinely been seen at our institution for nausea, vomiting and abdominal pain since 2003, presented with the complaint of nausea, vomiting and abdominal pain. She stated that the symptoms occurred this time after eating four bites of ice cream. …
Her physical exam was normal except for some mild epigastric tenderness which she attributed to her excessive vomiting. Laboratory studies including a comprehensive metabolic panel, amylase, lipase, and complete blood count were normal except for anemia, which had improved since her last admission. Urine studies, including urinalysis, were normal with a urine drug screen positive for delta-9-tetrohydrocannabinol (THC), benzodiazepines and opiates. Abdominal and chest x-rays were normal.
During the course of her admission, further investigation into her history revealed chronic marijuana use. She reported that long hot showers provided the only relief for her pain and nausea. She claimed that she took so many showers that her bathroom was growing excessive amounts of mold and mildew. Research into her medical records revealed an even more disturbing fact: excessive radiation exposure and medical cost. In total, she has had in excess of 97 abdominal x-rays, eight abdominal CT scans, two abdominal MRIs, an abdominal MRA, small bowel follow-through, three gastric emptying studies, four esophagogastroduodenoscopies (EGD), and three colonoscopies. Since 2003 these tests produced two abnormal findings: (1) the two most recent gastric emptying studies at 224 and 180 minutes (gastroparesis) and (2) gastritis/duodenitis on EGD. Throughout her complete sevenyear work-up, celiac sprue, peptic ulcer disease, Barrett’s esophagus, porphyrias, ischemic bowel disease, appendicitis, ulcerative colitis, Crohn’s disease and H. pylori infection have been excluded. The patient’s medical record indicated that since 2005 she has had 97 emergency room visits. Additionally, since 2007 she has had 42 admissions.
Emphasis added. This is a feature of many of the clinical Case Reports that cannot be ignored. The lack of awareness of cannabis as the causal agent is costly. In terms of the dollar costs of diagnosis and care and in terms of the drugs and invasive diagnostic procedures administered to the patient.
I don’t have access to Morris and Fisher (2013) which the Abstract states reports a single Case.
In trolling around on Google I ran across this comment in a pot user forum:
As far as symptoms are concerned, they began about 3 years ago when I would wake up feeling nauseated. Shortly after the nausea started, I’d vomit once and (after smoking) I would feel better. This continued off and on without me giving it much thought until February of this year, when I was floored by intractable vomiting for about 48 hours. I couldn’t keep anything down (not even water), and the only time I felt like I didn’t want to die was when I was in a hot shower. When the vomiting and nausea finally relented after that first episode, I chalked the experience up to acute gastroenteritis. However, about three days later, I woke up feeling nauseated. I went to work as usual, but by noon I was throwing up unstoppably again and had to go home. By the time evening came around, I could eat light food like white rice and slept. But as soon as I awoke the next morning, I had the same stomach pains and nausea. Again I went to work and again the unstoppable vomiting kicked in right around midday. The only thing that brought relief was a hot shower or bath. So long as I was under hot water, I felt alright.
This person details a history of medical workups and a bit of the recur/remit presentation before ending up with his conclusion:
At this point, I have been completely abstinent from ze herb for 5 days and I have already noticed improvement. Although I, too, was skeptical about CHS at first, I just do not know what else could be causing the problem. Although I absolutely love to get high, at my current weight/height (I am 6’1″ and 129lbs now) I am quickly running out of options. If I can’t find a solution to this problem soon, it will literally kill me. And I’ll be damned if I gonna become the first known death directly related to marijuana consumption.
Naturally, the other forum users express the usual incredulity we see from the leegalizeetmon crowd. It’s worth a read.
I also ran across this blog post from a person claiming to be an ER doc:
Since I have become aware of this association between marijuana use and CVS type presentations it has been my “good fortune” to care for nearly a dozen patients in the emergency department who self-reported diagnosis of CVS. Curiously, of these patients about 10 admitted active marijuana use, and the 2 who denied it had positive urine screenings for marijuana. This does not exactly make a case series, but is certainly another interesting observation. Of course, since the prevalence of marijuana use in our Emergency Department seems to approach 100% sometimes, this also may not be a statistically significant association!
I conclude with points I made in prior posts. At the moment, this syndrome is clearly quite rare considering estimates for chronic cannabis users worldwide. Some of this is due to lack of diagnosis..the Case Reports make very clear that an extended history of diagnostic investigation of more usual gastric disorders is typical prior to the identification of cannabis as the causal agent. But even so, very likely this is a rare reaction. Given that, it is not impossible that there is some as-yet-undetermined source of the chronic vomiting that is merely correlated with cannabis use. [In the event your imagination fails you, people tend to suggest moldy weed, herbicide/pesticide and/or contamination from smoking devices as causes.] Nevertheless, it appears to me to be likely that as we accumulate more and more Cases separated by time and place, which involve individual users with a variety of phenotypes and environmental circumstances, which present similar clinical pictures and which seem to have chronic cannabis smoking (not synthetic marijuana products, for example) as the only commonality…. well it becomes very difficult to sustain any alternative hypothesis.
Hickey JL, Witsil JC, Mycyk MB.Haloperidol for treatment of cannabinoid hyperemesis syndrome. Am J Emerg Med. 2013 Jun;31(6):1003.e5-6. doi: 10.1016/j.ajem.2013.02.021. Epub 2013 Apr 10. [link]
Mohammed F, Panchoo K, Bartholemew M, Maharaj D.Compulsive showering and marijuana use – the cannabis hyperemisis syndrome.Am J Case Rep. 2013 Aug 23;14:326-8. doi: 10.12659/AJCR.884001. [PMC link]
Enuh HA, Chin J, Nfonoyim J. Cannabinoid hyperemesis syndrome with extreme hydrophilia. Int J Gen Med. 2013 Aug 19;6:685-7. doi: 10.2147/IJGM.S49701. [OpenAccess link]
Sofka S, Lerfald N. Cannabinoid hyperemesis syndrome: A case series. W V Med J. 2013 May-Jun;109(3):20-3.
Gessford AK, John M, Nicholson B, Trout R. Marijuana induced hyperemesis: a case report. W V Med J. 2012 Nov-Dec;108(6):20-2. [link]
February 24, 2013