The effects of chronic marijuana use on circadian entrainment

Animal literature suggests a connection between marijuana use and altered circadian rhythms. However, the effect has not yet been demonstrated in humans. The present study examined the effect of chronic marijuana use on human circadian function. Participants consisted of current users who reported smoking marijuana daily for at least a year and non-marijuana user controls. Participants took a neurocognitive assessment, wore actigraphs and maintained sleep diaries for three weeks. While no significant cognitive changes were found between groups, data revealed that chronic marijuana use may act as an additional zeitgeber and lead to increased entrainment in human users.     

Legalize use of marijuana for medical purposes,MDs and patients plead

As debate about the legalization of marijuana continues in Canada, physicians are joining the fray. Ottawa family physician Don Kilby is working hard to make it easier for ill patients to use the marijuana that alleviates their symptoms. A recent case in Toronto indicates that the courts are starting to share these views.     

Traditional marijuana,high‐potency cannabis and synthetic cannabinoids: increasing risk for psychosis

Epidemiological evidence demonstrates that cannabis use is associated with an increased risk of psychotic outcomes, and confirms a dose‐response relationship between the level of use and the risk of later psychosis. High‐potency cannabis and synthetic cannabinoids carry the greatest risk. Experimental administration of tetrahydrocannabinol, the active ingredient of cannabis, induces transient psychosis in normal subjects, but this effect can be ameliorated by co‐administration of cannabidiol. This latter is a constituent of traditional hashish, but is largely absent from modern high‐potency forms of cannabis. Argument continues over the extent to which genetic predisposition is correlated to, or interacts with, cannabis use, and what proportion of psychosis could be prevented by minimizing heavy use. As yet, there is not convincing evidence that cannabis use increases risk of other psychiatric disorders, but there are no such doubts concerning its detrimental effect on cognitive function. All of the negative aspects are magnified if use starts in early adolescence. Irrespective of whether use of cannabis is decriminalized or legalized, the evidence that it is a component cause of psychosis is now sufficient for public health messages outlining the risk, especially of regular use of high‐potency cannabis and synthetic cannabinoids.     

The YouTube generation: implications for medical professionalism

While medical education has remained relatively constant over the past century, the rising popularity of internet-based technologies, such as applications for social networking, media sharing, or blogging, has drastically changed the way in which physicians-in-training interact with educators, peers, and the outside world. The implementation of these new technologies creates new challenges and opportunities for medical educators. Representation, the absence of established policies and legal precedents, and the perception of the lay public exemplify some of the issues that arise when considering the digital images used by trainees. While some of these issues affect higher education generally, medical schools are faced with additional challenges to ensure that graduates exemplify the ideals of medical professionalism. We present a case vignette with subsequent discussion to highlight the complexities of ensuring medical professionalism in the digital age.     

Neuropsychological effects of marijuana

This study assigned 81 non-naïve subjects, divided into low- and high-dose groups, to four experimental conditions (marijuana/marijuana, marijuana/placebo, placebo/marijuana and placebo/placebo) for two sessions separated by about one week. The low dose was 4.8 mg. Δ⁹-THC followed by 2.4 mg. one hour later. The high dose was 9.1 mg. followed by 4.5 mg. one hour later. A battery of neuropsychological tests was administered.The low dose produced generalized impairment of all mental processes (concept formation, memory, tactile form discrimination and motor function) and the effect was generalized to all modalities. The high dose resulted in more extensive impairment, again generalized.The drug effects noted were explained in terms of generalized impairment of central integrative processes. The effects of marijuana on learning as well as memory were explained in terms of impaired output (recall), but the impairment was transient.     

The effects of cannabinoids on the regulation of reproduction.

It has been shown that the main psychoactive component of marihuana, delta9-tetrahydrocannabinol (THC) has mainly inhibitory effects on the regulation of reproduction. Recently, the purification and availability of the endogenous ligand of the cannabinoid receptor, arachidonyl ethanolamide, anandamide, (ANA) and its specific long lasting antagonist, the SR 141716 (SR) provided us the opportunity to compare the effects of THC and ANA on the neuroendocrine regulation of reproduction. ANA decreases serum luteinizing hormone (LH) and prolactin (PRL) levels in rats of both sexes. It has no action on serum follicle stimulating hormone (FSH) level. When ANA was administered to pregnant rats it resulted in an increase of the duration of pregnancy and in the frequency of stillbirths. The postnatal development of hypothalamo-pituitary axis in offspring was temporarily inhibited. In conclusion, we found that exogenous and endogenous cannabinoids have only slightly different effects on the reproductive parameters. These effects may occur via the central cannabinoid receptor. It is possible that the sites of action are at both hypothalamic and pituitary levels. The results further support the view that ANA may be a central neurotransmitter or neuromodulator.     

The use of a complex thermohygrometric index in predicting adverse health effects in Athens

Mortality and morbidity indices are known to depend on changes in meteorological conditions. In Athens, severe adverse health effects following extreme heat conditions have been reported. The usefulness has been investigated of the complex thermohygrometric index (THI), a simple index based on maximum daily temperature and relative humidity, in predicting the health effects of specific meteorological conditions. The values of THI were found to correlate well with more complex bioclimatic indices; the THI could successfully replace temperature and humidity in predicting the daily number of deaths through multiple linear regression modelling. Thus the introduction of THI levels more than 28.5° C and between 26.5 and 28.5° C, through dummy variables, in a regression model explained 40% of the variability in the number of deaths during the months of July and August. During days with THI values less than 26.5° C the mean number of deaths was 33.5, compared to 41.8 when THI was between 26.5 and 28.5° C. The daily number of deaths increased to 108.2 when THI exceeded 28.5° C. From this study, the exact level of THI at which public health measures must be taken was not clear and more work is needed to identify it. However, given its simplicity, the use of THI for predicting meteorological conditions which are adverse to health would appear to be promising in preventive medicine and in health services planning.     

Sex differences in behavioral effects of cannabinoids

This review summarizes the existing literature on sex differences in the effects of cannabinoid drugs on behavior, primarily in the adult rodent. These preclinical studies, taken together with preliminary reports of sex differences in cannabinoid effects in humans, suggest that sex of subject may be an important modulating factor in a variety of cannabinoid effects. When sex differences are found, females are usually more sensitive than males to cannabinoids. Both pharmacokinetic and pharmacodynamic variables may contribute to sex differences in behavioral effects of cannabinoids. Given the significant therapeutic potential of cannabinoid agonists and antagonists--as well as their widespread recreational use--it will be important to determine the reliability and functional significance of, as well as mechanisms underlying sex differences in cannabinoid effects.     

The physiological effects of cigarette smoking: implications for psychophysiological research

The present study was designed to determine the specific physiological effects of two experimental conditions, smoking and mock smoking (puffing on an unlit cigarette), with smokers and nonsmokers. Two groups (smokers versus nonsmokers) with nine subjects each (five females, four males) participated in the present study. Physiological measures included alveolar carbon monoxide (COa) levels, skin resistance, heart rate, and finger temperature across a standard session sequence. The results of the COa assessment indicated increments only in the smoking condition. Multivariate analyses of variance (MANOVA) across skin conductance, heart rate, and hand temperature were initially performed, followed by univariate analyses of variance (ANOVA) for each physiological measure. Post hoc analyses were performed using orthogonal polynomial trend analyses. A number of significant differences were found. Discussion focuses on the need for experimental controls related to cigarette smoking in psychophysiological research in general, and in hand temperature biofeedback training in particular.     

Current and former marijuana use: preliminary findings of a longitudinal study of effects on IQ in young adults

Background

Assessing marijuana''s impact on intelligence quotient (IQ) has been hampered by a lack of evaluation of subjects before they begin to use this substance. Using data from a group of young people whom we have been following since birth, we examined IQ scores before, during and after cessation of regular marijuana use to determine any impact of the drug on this measure of cognitive function.

Methods

We determined marijuana use for seventy 17- to 20-year-olds through self-reporting and urinalysis. IQ difference scores were calculated by subtracting each person''s IQ score at 9–12 years (before initiation of drug use) from his or her score at 17–20 years. We then compared the difference in IQ scores of current heavy users (at least 5 joints per week), current light users (less than 5 joints per week), former users (who had not smoked regularly for at least 3 months) and non-users (who never smoked more than once per week and no smoking in the past two weeks).

Results

Current marijuana use was significantly correlated (p < 0.05) in a dose- related fashion with a decline in IQ over the ages studied. The comparison of the IQ difference scores showed an average decrease of 4.1 points in current heavy users (p < 0.05) compared to gains in IQ points for light current users (5.8), former users (3.5) and non-users (2.6).

Interpretation

Current marijuana use had a negative effect on global IQ score only in subjects who smoked 5 or more joints per week. A negative effect was not observed among subjects who had previously been heavy users but were no longer using the substance. We conclude that marijuana does not have a long-term negative impact on global intelligence. Whether the absence of a residual marijuana effect would also be evident in more specific cognitive domains such as memory and attention remains to be ascertained.Marijuana produces well-documented, acute cognitive changes that last for several hours after the drug has been ingested.^1,2,3 Whether it produces cognitive dysfunction beyond this period of acute intoxication is much more difficult to establish. Approaches to investigating long-lasting effects include clinical assessment of long-term users,^4,5,6 observations of subcultures in countries where long-term daily use of cannabis has been the cultural norm for decades^7,8,9 and marijuana administration studies in which subjects with a history of use ranging from infrequent to extensive are given the drug in controlled laboratory settings after various periods of abstinence.^10,11,12 As discussed in several reviews of the literature,^1,13,14 the findings have been equivocal.Most studies that examined heavy marijuana users for possible cognitive dysfunction lasting beyond the acute intoxication period assessed subjects after an abstinence period of only a day or two.^10,12,15,16 The fact that cannabinoid metabolites have been detected in the urine of long-term marijuana users after weeks or even months of abstinence^17,18,19 compromises the interpretation of these studies. To account for potential pre-existing differences between users and non-users, studies have typically matched the comparison group with the user group in terms of non-marijuana variables.^6,20 Suggestions for improving study designs^13,14 have emphasized both the need for comparison groups to be as similar as possible to the drug-using group and the need for a prolonged abstinence period. The most desirable procedure would involve a longitudinal, prospective design in which cognitive measures were available for all non-using and using subjects before and after marijuana consumption had been initiated by the users.¹⁵The Ottawa Prenatal Prospective Study (OPPS), underway since 1978, satisfies these criteria. This study permits both within-subject and between-subject comparisons among relatively low-risk non-users and users before, during and after quitting regular marijuana use. The primary objective of the OPPS is the neuropsychologic assessment of children exposed prenatally to marijuana or cigarettes. Women who used and did not use marijuana and cigarettes volunteered to participate during their pregnancy, and their children, now between the ages of 17 and 20 years, have been assessed since birth. Details of the recruitment of the largely middle-class families, the assessment procedures and the findings for the children from birth to adolescence have been summarized elsewhere.^21,22The objectives of the current study were as follows: to determine if current, regular marijuana use is predictive of decline in IQ from pre-usage levels, to determine if a differential effect on IQ occurs with heavy versus light current, regular marijuana use, and to determine if any IQ effects persist after subjects cease using marijuana for at least 3 months.     

Effects of cannabinoids (marijuana) on taste intensity and hedonic ratings and salivary flow of adults

Cannabinoids purportedly improve taste responsiveness and enhancethe sensory appeal of foods. These properties and a commonlycited oral drying effect were evaluated in a series of studieswith ‘light’ marijuana users. The first was a double-blind,placebo-controlled, acute oral dosing trial, involving an ageand gender stratified sample of 57 adults. An influence of routeof drug delivery was explored in another 11 individuals whowere administered a single dose orally, sublingually and viacigarette. To explore effects following chronic administration,six additional individuals were dosed twice per day for 3 daysorally and by rectal suppository. Taste intensity and hedonicresponses for sweet, sour, salty and bitter food stimuli weremonitored at baseline, 2, 4 and 6 hours post-dosing in the acutestudies, and daily in the chronic study. Stimulated saliva sampleswere collected at these same times. Salivary flow rate was significantlynegatively correlated with plasma drug levels, and reported‘high’ 2 and 4 h post-dosing. No effects of thedrug were observed on taste responses. Self-reported shiftsin taste responsiveness and hedonics may be related to alterationsof memory and cognition, rather than gustatory function.     

Chronotype: implications for sleep quality in medical students

ABSTRACT

Medical students who suffer from poor sleep quality may be afflicted by distress. While the change of chronotype may improve sleep quality, few studies have focused on this association. The objective of this study is to analyze the effects of chronotype on sleep quality in medical students while controlling for confounding covariate factors. A cross-sectional survey on sleep quality was conducted among 5497 medical students. Sleep quality, chronotype, and lifestyle were measured according to the Pittsburgh Sleep Quality Index, Morningness-eveningness Questionnaire and Health-promoting Lifestyle Profile. Hierarchical logistic regression was conducted to analyze the influence of various factors, especially chronotype effect on sleep quality. Our results showed that the total score of sleep quality in evening-types was 5.43 ± 2.66, which was significantly higher than that in morning-types (3.88 ± 2.20, P < .001). Morning-type students (OR = 0.40, 95%CI = 0.29–0.55) and intermediate-type students (OR = 0.53, 95%CI = 0.41–0.69) had a lower risk of poor sleep quality compared to evening-types. The strongest predictor of sleep quality was chronotype while controlling for covariates (grade, gender, father’s educational level, mother’s educational level, internet addiction, mood state, midnight snack frequency, and health-promoting lifestyle profile). Based on the results, we believe that sleep quality among evening-type students may be improved by shifting to keep early hours.