Substance use disorders: a comprehensive update of classification,epidemiology, neurobiology,clinical aspects,treatment and prevention

Substance use disorders (SUDs) are highly prevalent and exact a large toll on individuals’ health, well-being, and social functioning. Long-lasting changes in brain networks involved in reward, executive function, stress reactivity, mood, and self-awareness underlie the intense drive to consume substances and the inability to control this urge in a person who suffers from addiction (moderate or severe SUD). Biological (including genetics and developmental life stages) and social (including adverse childhood experiences) determinants of health are recognized factors that contribute to vulnerability for or resilience against developing a SUD. Consequently, prevention strategies that target social risk factors can improve outcomes and, when deployed in childhood and adolescence, can decrease the risk for these disorders. SUDs are treatable, and evidence of clinically significant benefit exists for medications (in opioid, nicotine and alcohol use disorders), behavioral therapies (in all SUDs), and neuromodulation (in nicotine use disorder). Treatment of SUDs should be considered within the context of a Chronic Care Model, with the intensity of intervention adjusted to the severity of the disorder and with the concomitant treatment of comorbid psychiatric and physical conditions. Involvement of health care providers in detection and management of SUDs, including referral of severe cases to specialized care, offers sustainable models of care that can be further expanded with the use of telehealth. Despite advances in our understanding and management of SUDs, individuals with these conditions continue to be stigmatized and, in some countries, incarcerated, highlighting the need to dismantle policies that perpetuate their criminalization and instead develop policies to ensure support and access to prevention and treatment.     

THE EVOLUTIONARY ECOLOGY OF AN ANTIPREDATOR REACTION NORM: DAPHNIA PULEX AND CHAOBORUS AMERICANUS

Ponds containing the parthenogenetic zooplankter Daphnia pulex with and without chaoborid predators were sampled over the course of a season. A significant (P < 0.05) Spearman rank correlation was found between predator density and the expression of an antipredator defense (neckteeth) by the Daphnia. The reaction norms (percent induction of a single genotype versus predator density) of clones isolated from predator-free and predator-rich habitats were determined in a laboratory setting. There was a statistically significant different response among the six clones tested (P < 0.05). Clones isolated from chaoborid ponds showed significantly greater sensitivity to the presence of predator than clones from predator-free ponds (P < 0.05). In the laboratory, food levels under which prey were cultured affected induction of the antipredator response. Highest induction was found at the lowest food level used.     

Patterns of parasitism among conopid flies parasitizing bumblebees

The effects of host size and host species on the prevalence and fitness of conopid flies (Diptera: Conopidae) parasitizing bumblebees (Hymenoptera: Apidae) were investigated. Field data from nine sites across south‐western Alberta, Canada, showed that conopids parasitized, on average, 12.3% of workers and 3.5% of male bees. In general, bee mass was a better predictor of host use and conopid offspring size than bee species. Host mass could not, however, explain the very low prevalence of conopids in the long‐tongued bumblebee, Bombus californicus Smith, or in male bees in general. Conopids predominately infested bees of intermediate size, and as a result, occurred most commonly in the intermediately sized species, B. flavifrons Cresson. Host quality, in terms of conopid offspring size, increased as a non‐linear function of bee size. The results are discussed with respect to the impact of conopids on bumblebee populations, and the relation between host quality and patterns of host use.     

Non‐target habitat exploitation by Trichogramma brassicae (Hym. Trichogrammatidae): what are the risks for endemic butterflies?

Abstract 1 Trichogramma brassicae Bezdenko is inundatively released against the European corn borer in Switzerland. Because parasitoids dispersing from the release fields might pose a threat to native butterflies, the searching efficiency of T. brassicae was investigated in nontarget habitats. 2 In field studies, T. brassicae was released at rates of 120 000 females/ha. Parasitism of sentinel Ephestia kuehniella egg clusters was 1.6–3.6% in meadows and 2.0–4.0% in flower strips. The respective figures were 57.6–66.7% and 19.2–46.9% in maize, significantly higher than the parasitism rates in the nontarget habitats. Experiments carried out in small field cages confirmed these results: Again, significantly higher parasitism rates were found in maize compared to meadows and flower strips, and also compared to hedgerows (in sleeve cages). 3 To elucidate potential factors underlying the low searching efficiency in nontarget habitats, the behaviour of individual T. brassicae females was investigated on four meadow plants comparatively to maize and a filter paper control. Mean (±SE) walking speed on maize was 2.2 ± 0.2 mm/s, similar to three of the plants tested and filter paper but significantly higher than on Trifolium pratense (0.85 mm/s). A higher turning rate was found on T. pratense, Viola wittrockiana and Plantago lanceolata, in contrast to the longer leaved maize and Alopecurus pratensis. The number of wasps leaving the plant within the observation period differed significantly between plant species, and was twice as high for T. pratense (and the filter paper control) compared to the other plant species. 4 In a choice experiment carried out in a climate cabinet with all five host plant species in cages, we obtained the highest parasitism rates on maize and the lowest parasitism on T. pratense, thus confirming the behavioural observations. 5 In conclusion, there is evidence for a decreased searching efficiency on plants in nontarget habitats compared to maize. However, the data explain only part of the differences found between parasitism in maize compared to nontarget habitats. Other factors, such as the structural complexity of a habitat, may also play a role. We conclude that the risk for butterfly populations in the tested nontarget habitat due to mass released T. brassicae is low.     

Birth Weight and Its Relationship to Size Attained and Relative Fat Distribution at 7 to 12 Years of Age

The relationship between birth weight and relative subcutaneous fat distribution at school age was considered in 131 boys and 106 girls 7 to 12 years of age. Relative fat distribution at school age was estimated with the ratio of the subscapular to triceps skinfolds (S/T) for the total sample, and with the ratio of the sum of two trunk (subscapular, midaxillary) to the sum of two extremity (triceps, medial calf) skinfolds (T/E) for subsamples of 102 boys and 63 girls. There were no sex differences in the S/T ratio (mm/mm), boys 0.62 ± 0.15, girls 0.63 ± 0.18; T/E ratio (mm/mm), boys 0.58 ± 0.13, girls 0.59 ± 0.16; and BMI (kg/m²), boys 17.1 ± 2.4, girls 16.9 ± 2.2. Second order partial correlations, controlling for age and the BMI or age and sum of skinfolds, between birth weight and the skinfold ratios are, respectively, ?0.22 and ?0.20 (p<0.01) for S/T and ?0.29 and ?032 (p<0.01) for T/E in girls, and ?0.18 and ?0.17 (p<0.05) for S/T and ?0.06 and ?0.6 for T/E in boys. Though low, the correlations suggest that as birth weight decreases proportionally more subcutaneous fat is accumulated on the trunk than on the extremities, more so in females than in males. Results of stepwise multiple regression analyses indicate that birth weight accounts for from 2% to 8% of the variance in relative subcutaneous fat distribution at school age.     

Protein Synthesis in Euglena gracilis is Light-and Temperature-Dependent,Oscillating in a Circadian,Temperature-Compensated Manner

Abstract: Incorporation of radiolabelled amino acids into proteins of Euglena gracilis revealed that the amount of labelled protein depends on the conditions of illumination and temperature of cultivation. Protein synthesis was generally lower under dark conditions except at 37 °C. The largest amounts of labelled protein were measured at 21 °C and decreased at higher and lower temperatures. By separating the labelled proteins of the membraneous cell fraction from subcultures under a range of culture conditions, the synthesis of some specific proteins was found to be light- and/or temperature-dependent. On incubating cells taken at different times during a light/dark cycle and under constant conditions, a circadian rhythm of ³⁵S-methionine- as well as ³⁵S-cysteine-incorporation was detected. Thereby the cells incorporated ten-times less cysteine than methionine. Protein synthesis always peaked during the last quarter of the daily light phase, confirming the rhythmic rise in total protein. The length of the rhythm period, approximately 24 h, was nearly independent of the applied temperature in the range of 16 to 27 °C.     

Environmental risk assessment of releases of transgenic plants containing virus-derived inserts

Sequences derived from the genomes of plant viruses are being used to provide virus resistance in transgenic crop plants. Although the environmental hazards associated with the release of such plants have been discussed widely, it has not been possible to reach generally acceptable conclusions about their safety. A case-by-case approach to the risk assessment of real examples is recommended as a means of building up confidence and of indicating areas of uncertainty. A logical framework for risk assessment is suggested, a key feature of which is identification of the viruses in the release environment that may infect the transgenic plants. Each of these is considered in relation to each of the three main classes of hazard (transcapsidation, recombination and synergism), and the risk associated with each event is analysed.     

Behavioral responses of a sex-role reversed pipefish to a gradient of perceived predation risk

Conspicuous behaviors such as courtship and mating often makeanimals susceptible to predation. When perceiving themselvesat an elevated level of risk, animals frequently reduce conspicuousbehaviors in tradeoff for a decrease in probability of beingpreyed upon. In the present study, we used two experiments toexamine the effect of perceived predation risk from cod (Gadusmorhud) on nonreproductive and reproductive behaviors in thesex-role reversed pipefish (Syngnathus typhle). In the firstexperiment, no differences due to predation risk were detectedin the nonreproductive behaviors of either males or females.In the second experiment, predation risk had significant effectson reproductive behaviors. Pipefish were allowed to court andcopulate at four different predation levels. We created predationlevels differing in perceived predation risk by controllingthe number of sensory modes through which pipefish could detectthe presence of a cod. As predation risk increased, pipefishcopulated and courted less frequently, swam alone (displayedand searched for conspecifics) less often, and waited longerbefore commencing courtship. These changes in behavior minimizedthe amount of time spent above the eelgrass and presumably reducedconspicuousness to visual predators. Pipefish also copulatedafter a smaller amount of courtship as predation risk increased,indicating that they may trade information concerning mate qualityfor a reduction in predation risk. No differences were foundin any response variable between males and females. The roleof operational sex ratios and intersexual competition in determiningwhich sex assumes greater costs in mate acquisition is questioned.     

Human Interindividual Variability in Cancer Risks—Technical and Management Challenges

Existing risk assessment procedures for carcinogens are intended to be “conservative” in the uncertainty dimension—giving estimates that are expected to be higher than true risks for typical people. However, these procedures do not consider the likely variability in susceptibility among individual people. This paper updates previous estimates of the likely extent of this variability for metabolically activated, genetically-acting carcinogens based on recent information on human interindividual variability in metabolic activation, detoxification, and DNA repair. The resulting expected skewness of cancer risk distributions is estimated using Monte Carlo simulations of both variability and uncertainty.

Some risk management implications are:

1. When evaluating the fairness of a particular risk distribution, managers need to gain familiarity with a three-dimensional characterization—X level of risk, for the Yth percentile individual (addressing variability) with Z degree of confidence (addressing uncertainty).

2. To the extent that variability distributions are skewed (e.g., with a long tail extending to high values) population mean risks will tend to exceed risks for median individuals. Together with the skewness in uncertainty distributions, this implies that “expected value” estimates of aggregate population risks—the estimates of interest for cost benefit analyses—are likely to be closer to traditional upper confidence limit risk estimates than has often been assumed in the past.