We thank Beckson et al. for their thoughtful comments 1, and agree with the need for more research on cannabis, especially with respect to driving. Our goal was to provide an unbiased, policy-relevant estimate of the risk of crashing associated with tetrahydrocannabinol (THC) levels obtained within a realistic time after a collision. We aimed to minimize or eliminate many of the biases found in previous research. The responsibility analysis design minimizes the problem of differential ascertainment of THC in cases versus controls. Unlike some previous studies, we adjusted for multiple confounders (age, sex, other substance use). We measured THC in blood obtained for clinical purposes with waiver of consent, eliminating potential bias from high refusal rates common in previous research, and minimizing the time from collision to blood draw. Despite the limitations that Dr Beckson correctly indicates, blood THC levels are more meaningful than urine or oral fluid cannabis tests, which is why we chose this biological sample. We acknowledge that the THC levels in our study are less than at time of crash. THC levels decline rapidly in during the first hour after smoking, as THC distributes into the body tissue, and then decline more slowly as THC is eliminated. In our study the median time from crash until blood draw was 84 minutes, and 76% of samples were obtained within 2 hours, a significant improvement over previous research.2-5 For drivers smoking cannabis in the vehicle, THC levels in our study would be lower than at time of collision. However, if there was a delay of more than an hour between smoking and collision, THC levels would decline more slowly and the drop in THC between collision and blood draw would be less. Most importantly, it is unlikely that blood samples could be obtained more quickly for law enforcement purposes than for medical reasons. Hence, our risk estimates are based on THC levels obtained within a feasible time after collision and are relevant to evaluating enforceable per se limits. Beckson states, without reference, that postmortem THC concentrations more accurately reflect concentration at time of crash ‘because circulation and metabolism ceases with death’. This statement is misleading, and we disagree strongly with the implication that postmortem studies yield more meaningful results; in fact, the opposite is probably true. People may survive for hours following a collision and there will be ongoing distribution and metabolism of THC during that time. In the Vancouver region, where many of our cases came from, 50% of trauma deaths occur more than 6 hours after injury 6. Beckson cites a postmortem study by Drummer et al. [10] that yielded an odds ratio (OR) of 6.1 for drivers with THC > 5 ng/ml. That study included drivers who survived up to 4 hours after the collision 7, 8. Equally importantly, THC undergoes significant postmortem redistribution as it diffuses from body stores into blood. The extent of postmortem distribution depends on the time from death until blood is obtained and on the body site where blood is obtained from 9, 10. As such, THC levels in postmortem blood correlate poorly with THC concentration at time of death,9 and antemortem hospital samples, when available, are more reliable 10. We also point out that studying non-fatal crashes is important, because the vast majority of collisions are non-fatal and the likelihood of surviving a collision has increased substantially with advances in automotive safety (crumple zones, airbags) and improvements in trauma systems and care. Beckson describes our study as underpowered. This might be said of virtually every study with a modest association and no statistical significance. The important questions are whether our methods were valid and the findings meaningful. We analyzed blood THC levels in a large sample (1825) of crash involved drivers with determinate crash responsibility. For drivers with THC < 5 ng/ml (n = 145), confidence intervals were narrow and there was no evidence of increased risk. Only 20 drivers (1.0%) had THC > 5 ng/ml and the OR was not significant for those drivers. In contrast, risk was substantially elevated (OR = 6.0; P < 0.01) in the 241 drivers (13.2%) with BAC > 0.08%.11 Hence our conclusion that the impact of cannabis on road safety is relatively small. Compared with alcohol, this is a fair conclusion. Beckson also criticizes our use of pre-legalization data. We see no plausible reason that the collision risk associated with cannabis will change following legalization. As discussed in the paper, we acknowledge that the overall road safety impact of cannabis may increase if more people drive after using cannabis, especially if they also use alcohol. We are collecting post-legalization data using identical methods to test for this possibility. None.

The proper description of former populations is one of the most difficult tasks in anthropology. Archaeological material is often limited due to fragmented and sometimes poorly preserved bone material resulting in incomplete data. Published skeletal raw data are available from the past, but much of this data is either unavailable or not used for scientific studies. The authors seek to elicit more information about prehistoric times by using this dataset to introduce a new method. The purpose is to provide an approach to reconstruct a former population in respect to robusticity and health status. For this in the pilot study the Body Mass Index (BMI) and Frame Index (FI) of early medieval South-West Germany have been analysed. The FI, in contrast to the BMI, has not yet been used for robusticity analysis utilizing only skeletal remains. As far as we know, this is the first time that the FI has been calculated using archaeological material. Due to unknown soft-tissue thickness we introduce the Osseous Frame Index (OFI). The measured OFI reveals new insights in (pre-)historic populations and allows comparisons with modern reference samples. Our OFI calculations are relatively similar to modem calculations. Males have a higher robusticity than females, slightly increasing during life-time compared to females. These calculations provide a better historical understanding of human body composition.

The 2008 U.S. presidential campaign featured “change we can believe in,” and the global marketplace and shifting economy have resulted in additional calls for change in many policies and paradigms. Political and economic issues influence education and result in modifications for schools, teachers, and students. Such developments, as well as rapid advances in technology, impact the way we teach and learn mathematics.

Orbital exenteration after craniofacial tumor resection is a common reconstructive dilemma that often results in immediate and long-term high patient dissatisfaction. Traditional reconstructive options have centered on adhesive-retained prostheses. Craniofacial implant technology offers the patient improved reconstructive options. We describe a technique used in a series of patients in whom craniofacial implant-retained prostheses were utilized following orbital exenteration. A computer-assisted navigational system was used to place two to three endosseous craniofacial implants in the remaining orbital rim. Following osseointegration, a patient-specific magnet-retained orbital prosthesis was custom fabricated. All patients reported excellent prosthesis handling and stability. This represents a significant improvement in patient satisfaction and psychosocial well-being after complex craniofacial surgery.

Attitudes toward compulsory treatment for alcohol and other drug abuse were compared among a representative sample drawn from the general public (N = 994) and convenience samples of substance abuse counselors (N = 700), probationers (N = 35) and judges (N = 89). All respondents believed that compulsory substance abuse treatment is (a) less effective than voluntary treatment and (b) most justified only for individuals whose substance use was associated with serious crimes and impaired job performance. In addition, the general public reported significantly higher support for compulsory treatment and expected forced treatment to help significantly more individuals, compared to probationers and substance abuse counselors. Judges and the general public were significantly less likely to respect client choices about whether or not to engage in treatment compared to probationers and substance abuse counsellors. These results suggest that broad implementation of compulsory substance abuse treatment policies and programs would not be uniformly supported across key stakeholders. Implications of the findings for substance abuse policy, programming and theory are discussed.

While cannabis is the most frequently found illegal drug in drivers killed or injured in motor vehicle collisions, little is know about driving under the influence of cannabis (DUIC) in the general population. We report information on the incidence of DUIC in a representative sample of the Ontario adult population. Among all drivers, 1.9% reported DUIC in the previous 12 months. Several factors influenced the likelihood of reported DUIC, including gender, age, marital status and education level. Among cannabis users, DUIC appeared to be a relatively common behaviour; 22.8% reported DUIC, and the probability of the behaviour was significantly influenced by gender and education level. As well, DUIC and drinking-driving were strongly related in this sample. These data underscore the need to obtain more information on this behaviour, including a more complete understanding of any risks involved.

DANS CE NUMERO (PAGE 1529) le Dr Christiane Poulin et ses collegues signalent qu’en 1994, 4,1 % des Canadiens etaient alcooliques et que, de ce nombre, pres de 85 % ne suivaient pas de traitement. Cette situation indique le besoin pour les medecins de soins primaires d’utiliser davantage le depistage et de breves interventions face aux problemes d’alcool. La perception generale d’inefficacite de ces types d’interventions a fait obstacle a leur utilisation. Cependant, selon de nombreuses etudes documentees, ces interventions contribueraient effectivement a diminuer les problemes de sante lies a l’alcool chez les patients et dans la population. Meme si aucune intervention particuliere ne s’applique a tous les patients, les avantages eventuels generaux d’une intervention accrue en cas d’alcoolisme sont enormes.

The impact of sentence severity on the driving behavior of offenders remains unclear despite the increase in penalties for drinking driving offences in numerous jurisdictions during the past years. In this research, relationships between sentences (license suspension, fine, jail term, assignment to probation or temproary absence programs) and post-adjudication drinking-driving convictions for alcohol-related and total collisions were examined, while controlling statistically for demographic and previous driving record factors. Licence suspensions are consistently related with traffic safety benefits. However, increased severity of other types of punishment seemed unrelated to outcome, or with increasing traffic safety problems. Further, important differences between first, second and multiple offenders were observed which may be associated with the impact of different aspects of sentence severity on driving behavior.

An approach to nonmonotonic reasoning in expert systems is presented that does not rely on numerical probabilities or confidence factors, using instead rules-of-thumb that cover the normal or typical case but are known to have exceptions. A logic for such defeasible rules is implemented in d-Prolog, an extension of Prolog. FORE, a prototype, knowledge-based system written in d-Prolog, is also presented. FORE uses ordinary Prolog rules to specify when a business forecasting method is indicated or counterindicated. A small kernel of defeasible metarules controls FORE's final recommendations.<>

Research designs, assessment instruments, and follow-up procedures for the evaluation of D.W.I. rehabilitation programmes are considered and the results of these programmes are reviewed. While evaluations of the rehabilitation programmes have been hindered by methodological difficulties, the information presently available indicates that certain of these programmes may reduce recidivism in D.W.I. offenders. These results need to be replicated in future well-controlled studies; methods for assessing which individuals would benefit most from specific programmes are also required.