An evaluation of the sensitivity of the Standardised Field Sobriety Tests (SFSTs) to detect impairment due to marijuana intoxication

Effects of acute cannabis inhalation on reaction time, decision-making, and memory using a tablet-based application

BACKGROUND

Acute cannabis use has been demonstrated to slow reaction time and affect decision-making and short-term memory. These effects may have utility in identifying impairment associated with recent use. However, these effects have not been widely investigated among individuals with a pattern of daily use, who may have acquired tolerance. The purpose of this study was to examine the impact of tolerance to cannabis on the acute effects as measured by reaction time, decision-making (gap acceptance), and short-term memory.

METHODS

Participants (ages 25-45) completed a tablet-based (iPad) test battery before and approximately 60 min after smoking cannabis flower. The change in performance from before to after cannabis use was compared across three groups of cannabis users: (1) occasional use (n = 23); (2) daily use (n = 31); or (3) no current use (n = 32). Participants in the occasional and daily use group self-administered ad libitum, by smoking or vaping, self-supplied cannabis flower with a high concentration of total THC (15-30%).

RESULTS

The occasional use group exhibited decrements in reaction time (slowed) and short-term memory (replicated fewer shapes) from before to after cannabis use, as compared to the no-use group. In the gap acceptance task, daily use participants took more time to complete the task post-smoking cannabis as compared to those with no use or occasional use; however, the level of accuracy did not significantly change.

CONCLUSIONS

The findings are consistent with acquired tolerance to certain acute psychomotor effects with daily cannabis use. The finding from the gap acceptance task which showed a decline in speed but not accuracy may indicate a prioritization of accuracy over response time. Cognitive and psychomotor assessments may have utility for identifying impairment associated with recent cannabis use.

Drug driving: a secondary analysis of factors associated with driving under the influence of cannabis in Jamaica

OBJECTIVES

To determine cannabis use patterns, the predictive sociodemographic correlates of driving under the influence of cannabis (DUIC) and the association between risk perception and cannabis dependence among vehicle drivers in Jamaica.

DESIGN

Secondary data analysis.

SETTING

Used the Jamaica National Drug Prevalence Survey 2016 dataset.

PARTICIPANTS

1060 vehicle drivers extracted from the population sample of 4623.

PRIMARY AND SECONDARY OUTCOME MEASURES

Analysis used Pearson's χ2 test and logistic regression. ORs and 95% CIs were recorded. A p<0.05 was considered statistically significant.

RESULTS

More than 10% of Jamaican drivers admitted to DUIC in the past year. Approximately 43.3% of drivers who currently use cannabis reported DUIC only. Evidently, 86.8% of drivers who DUIC were heavy cannabis users. Approximately 30% of drivers with moderate to high-risk perception of smoking cannabis sometimes or often were dependent on cannabis. Notwithstanding, drivers with no to low-risk perception of smoking cannabis sometimes or often were significantly likelier to be dependent (p<0.001 and p<0.001, respectively). Logistic regression highlighted male drivers (OR 4.14, 95% CI 1.59 to 14.20, p=0.009) that were 34 years and under (OR 2.97, 95% CI 1.71 to 5.29, p<0.001) and were the head of the household (OR 2.22, 95% CI 1.10 to 4.75, p=0.031) and operated a machine as part of their job (OR 1.87, 95% CI 1.09 to 3.24, p=0.023) were more likely to DUIC, while those who were married (OR 0.42, 95% CI 0.22 to 0.74, p=0.004) and had achieved a tertiary-level education (OR 0.26, 95% CI 0.06 to 0.76, p=0.031) were less likely.

CONCLUSIONS

Two in five Jamaican drivers, who currently smoke cannabis, drive under its influence, with over 85% engaging in heavy use. Public health implications necessitate policy-makers consider mobile roadside drug testing and amending drug-driving laws to meet international standards.

Enhancing the Standardized Field Sobriety Test to detect cannabis impairment: An observational study

OBJECTIVE

The purpose of this study was to explore various tests of impairment that could potentially be added to the Standardized Field Sobriety Test (SFST) to enhance its sensitivity to identify drivers whose abilities are adversely affected by cannabis.

METHODS

An observational study was conducted in which participants were invited to use their own cannabis at the research facility. Once prior to cannabis use and at four times during the 150 min after cannabis use, participants performed the three tests of the Standardized Field Sobriety Test (SFST) (i.e., Horizontal Gaze Nystagmus, Walk and Turn, and One Leg Stand) as well as the Modified Romberg Balance and Finger to Nose tests. In addition, assessments were made of physiological indicators (i.e., eyelid, leg and body tremors, rebound dilation, lack of convergence) and vital signs (pulse, blood pressure and body temperature). Participants also completed a digit-symbol substitution task at each testing interval. With the exception of vital signs and the digit symbol task, all tests and assessments were administered and scored by certified Drug Recognition Experts using the standard procedures of the Drug Evaluation and Classification Program.

RESULTS

Twenty minutes after vaping cannabis (mean THC concentration = 6.34 ng/mL), participants displayed performance deficits on a variety of tasks; 67% met the criterion for suspected impairment on the SFST. Addition of the Finger-to-Nose (FTN) test along with observations of head movements and jerks (HMJ) increased the percentage of participants who met the criterion for suspected impairment by 33% and improved the sensitivity of the test from 0.67 to 0.88.

CONCLUSIONS

The results of this study support supplementing the SFST with the Finger-to-Nose test and observations of HMJ to assist in the detection of drivers who are adversely affected by the use of cannabis. The observational study design and the use of assessors who were not blinded as to the use of cannabis by participants limits the strength of the evidence. Further research, including randomized trials and field studies of drivers, is required to confirm and validate this enhanced version of the SFST.

Evaluation of Field Sobriety Tests for Identifying Drivers Under the Influence of Cannabis: A Randomized Clinical Trial

Importance

With increasing medicinal and recreational cannabis legalization, there is a public health need for effective and unbiased evaluations for determining whether a driver is impaired due to Δ9-tetrahydrocannabinol (THC) exposure. Field sobriety tests (FSTs) are a key component of the gold standard law enforcement officer-based evaluations, yet controlled studies are inconclusive regarding their efficacy in detecting whether a person is under the influence of THC.

Objective

To examine the classification accuracy of FSTs with respect to cannabis exposure and driving impairment (as determined via a driving simulation).

Design, Setting, and Participants

This double-blind, placebo-controlled parallel randomized clinical trial was conducted from February 2017 to June 2019 at the Center for Medicinal Cannabis Research, University of California, San Diego. Participants were aged 21 to 55 years and had used cannabis in the past month. Data were analyzed from August 2021 to April 2023.

Intervention

Participants were randomized 1:1:1 to placebo (0.02% THC), 5.9% THC cannabis, or 13.4% THC cannabis smoked ad libitum.

Main Outcome and Measures

The primary end point was law enforcement officer determination of FST impairment at 4 time points after smoking. Additional measures included officer estimation as to whether participants were in the THC or placebo group as well as driving simulator data. Officers did not observe driving performance.

Results

The study included 184 participants (117 [63.6%] male; mean [SD] age, 30 [8.3] years) who had used cannabis a mean (SD) of 16.7 (9.8) days in the past 30 days; 121 received THC and 63, placebo. Officers classified 98 participants (81.0%) in the THC group and 31 (49.2%) in the placebo group as FST impaired (difference, 31.8 percentage points; 95% CI, 16.4-47.2 percentage points; P < .001) at 70 minutes after smoking. The THC group performed significantly worse than the placebo group on 8 of 27 individual FST components (29.6%) and all FST summary scores. However, the placebo group did not complete a median of 8 (IQR, 5-11) FST components as instructed. Of 128 participants classified as FST impaired, officers suspected 127 (99.2%) as having received THC. Driving simulator performance was significantly associated with results of select FSTs (eg, ≥2 clues on One Leg Stand was associated with impairment on the simulator: odds ratio, 3.09; 95% CI, 1.63-5.88; P < .001).

Conclusions and Relevance

This randomized clinical trial found that when administered by highly trained officers, FSTs differentiated between individuals receiving THC vs placebo and driving abilities were associated with results of some FSTs. However, the high rate at which the participants receiving placebo failed to adequately perform FSTs and the high frequency that poor FST performance was suspected to be due to THC-related impairment suggest that FSTs, absent other indicators, may be insufficient to denote THC-specific impairment in drivers.

Trial Registration

ClinicalTrials.gov Identifier: NCT02849587.

Effect of CannEpil® on simulated driving performance and co-monitoring of ocular activity: A randomised controlled trial

BACKGROUND

Medicinal cannabis products containing Δ9-tetrahydrocannabinol (THC) are increasingly accessible. Yet, policy guidelines regarding fitness to drive are lacking, and cannabinoid-specific indexations of impairment are underdeveloped.

AIMS

To determine the impact of a standardised 1 mL sublingual dose of CannEpil^®, a medicinal cannabis oil containing 100 mg cannabidiol (CBD) and 5 mg THC on simulated driving performance, relative to placebo and whether variations in vehicle control can be indexed by ocular activity.

METHODS

A double-blind, within-subjects, randomised, placebo-controlled, crossover trial assessed 31 healthy fully licensed drivers (15 male, 16 female) aged between 21 and 58 years (M = 38.0, SD = 10.78). Standard deviation of lateral position (SDLP), standard deviation of speed (SDS) and steering variability were assessed over time and as a function of treatment during a 40 min simulated drive, with oculomotor parameters assessed simultaneously. Oral fluid and plasma were collected at 30 min and 2.5 h.

RESULTS

CannEpil did not significantly alter SDLP across the full drive, although increased SDLP was observed between 20 and 30 min (p < 0.05). CannEpil increased SDS across the full drive (p < 0.05), with variance greatest at 20-30 min (p < 0.001). CannEpil increased fixation duration (p < 0.05), blink rate (trend p = 0.051) and decreased blink duration (p < 0.001) during driving. No significant correlations were observed between biological matrices and performance outcomes.

CONCLUSIONS

CannEpil impairs select aspects of vehicle control (speed and weaving) over time. Alterations to ocular behaviour suggest that eye tracking may assist in determining cannabis-related driver impairment or intoxication. Australian and New Zealand Clinician Trials Registry, https://anzctr.org.au(ACTRN12619000932167).

A Video Segmentation Pipeline for Assessing changes in Pupil Response to Light After Cannabis Consumption

Due to long-standing federal restrictions on cannabis-related research, the implications of cannabis legalization on traffic and occupational safety are understudied. Accordingly, there is a need for objective and validated measures of acute cannabis impairment that may be applied in public safety and occupational settings. Pupillary response to light may offer an avenue for detection that outperforms typical sobriety tests and THC concentrations. We developed a video processing and analysis pipeline that extracts pupil sizes during a light stimulus test administered with goggles utilizing infrared videography. The analysis compared pupil size trajectories in response to a light for those with occasional, daily, and no cannabis use before and after smoking. Pupils were segmented using a combination of image pre-processing techniques and segmentation algorithms which were validated using manually segmented data and found to achieve 99% precision and 94% F-score. Features extracted from the pupil size trajectories captured pupil constriction and rebound dilation and were analyzed using generalized estimating equations. We find that acute cannabis use results in less pupil constriction and slower pupil rebound dilation in the light stimulus test.

An electrochemical aptasensor for Δ9-tetrahydrocannabinol detection in saliva on a microfluidic platform

We present a novel "on-off", cost-effective, rapid electrochemical aptasensor combined with a microfluidics cartridge system for the detection of Δ⁹-THC (Δ⁹-tetrahydrocannabinol) in human saliva via differential pulse voltammetry. The assay relied on the competitive binding between the Δ⁹-THC and a soluble redox indicator methylene blue, using an aptamer selected via FRELEX. We found that the aptasensor can detected 1 nM of Δ⁹-THC in PBS in a three-electrode cell system, while the sensitivity and both the dissociation constant (K_d) and association constant (K_b) were dependent on the aptamer density. The aptamer also showed great affinity towards Δ⁹-THC when tested against cannabinol and cannabidiol. The same limit of detection of 1 nM in PBS was achieved in small volume samples (∼60 μL) using the aptamer-modified gold screen-printed electrodes combined with the microfluidic cartridge setup, however, the presence of 10% raw human saliva had a negative effect which manifested in a 10-fold increase in the LOD due to interfering elements. Filtering the saliva, improved the tested volume to 50% and the LOD to 5 nM of Δ⁹-THC which is lower than the concentrations associated with impairment (6.5-32 nM). The aptasensor showed a good storage capability up to 3 days, however, the reusability significantly dropped from 10 cycles (freshly prepared) to 5 cycles. The results clearly demonstrate the feasibility of the aptasensor platform with the microfluidics chamber towards a point-of-care testing application for the detection of Δ⁹-THC in saliva.

Waiting for the Stop Sign to Turn Green: Contemporary Issues on Drug and Alcohol Impaired Driving Policy

Impaired driving has been a considerable social problem in the U.S. for decades, but efforts to reduce it have stalled after the initial reductions in the 1980's. As a result, legislators continue to develop more polices aimed at deterring impaired driving. Although alcohol has historically been the focus of these efforts, recently there has been increased concern about marijuana impaired driving policies as well. However, alcohol and marijuana impaired driving differ in many ways. This paper explores the costs and benefits of new zero-tolerance policies such as the reduction of the per-se Blood Alcohol Concentration (BAC) level from .08 to .05 for alcohol and the establishment of similar per-se limits for marijuana. These policies are not based on actual impairment and reflect a net widening effect that will criminalize unimpaired drivers, divert criminal justice resources away from the most problematic impaired drivers, and will have little impact on impaired driving crashes. As such, they have the potential to do more harm than good.

The effects of oral and vaporized cannabis alone, and in combination with alcohol, on driving performance using the STISIM driving simulator: A two-part, double-blind, double-dummy, placebo-controlled, randomized crossover clinical laboratory protocol

The legalization of cannabis for medicinal and non-medicinal purposes, and the corresponding increase in diversity of cannabis products, has resulted an urgent need for cannabis regulatory science. Among the most pressing needs is research related to impairment due to cannabis exposure, especially on driving performance. The present project was designed to evaluate the impact of oral and vaporized cannabis, when administered alone or in combination with alcohol, on simulated driving performance (STISIM driving simulator), cognitive/psychomotor ability, and field sobriety performance. Healthy adults will complete two, double-blind, double-dummy, placebo-controlled, randomized crossover clinical laboratory studies, one with oral cannabis (16 men/16 women) and the second with vaporized cannabis (16 men/16 women). In each study, participants will complete seven experimental sessions during which acute doses of placebo or high Δ9-THC cannabis containing 0, 10, or 25 mg Δ9-THC will be administered both alone and in combination with placebo or alcohol-containing beverages (target breath alcohol concentrations, BAC, of 0.0% or 0.05%). A positive control session (i.e., alcohol at target BAC of 0.08% with placebo cannabis) will also be completed. Simulated driving performance tests (available for download; see Methods), field sobriety assessments, subjective drug effect questionnaires, a mobile device impairment test (DRUID app), and collection of whole blood specimens will be completed repeatedly during each session. Linear mixed models will be used to test for differences across experimental conditions and a priori planned comparisons will be used to determine differences between conditions of interest (e.g., cannabis alone vs cannabis with alcohol). This research is designed to extend prior studies of cannabis and alcohol on driving performance by using oral and vaporized routes of cannabis administration. By increasing understanding of impairment associated with co-use of alcohol and these novel forms of cannabis, this research could inform impairment detection standards for cannabis and alcohol and have important implications for law enforcement, public policy decisions regarding accessibility of these substances, and education of the general population who may use cannabis and/or alcohol. Lastly, this manuscript provides interested researchers with access to the simulated driving scenarios and data extraction tools developed for this study as a means of facilitating future cross-study comparisons, which is important given the heterogeneity in methods used across laboratories in prior research.

Effects of High-Potency Cannabis on Psychomotor Performance in Frequent Cannabis Users

Background: Recently increased access to cannabis products in the United States has been associated with increased rates of driving after cannabis use. Although numerous studies indicate that cannabis impairs psychomotor and neurocognitive functions that can affect driving ability, the determination of cannabis-impaired driving risk is complicated by the extent to which frequent cannabis users develop tolerance to THC's subjective, cognitive, and psychomotor effects, and by the fact that there is no validated behavioral or biological marker of recent cannabis use or cannabis-related impairment. This study examined the psychomotor impairment-related effects experienced by frequent cannabis users in Colorado after naturalistic consumption of smoked cannabis, both immediately and 1 h postuse. Results were then validated in a smaller replication sample from Washington state. Methods: In the primary Colorado study, participants (n=70) used the DRUID^® mobile app, a brief measure of psychomotor and cognitive domains that are sensitive to the effects of cannabis. First, participants used DRUID to establish a sober baseline impairment score. During a second appointment, they used DRUID at three time points: preuse, immediately after acutely using cannabis, and 1 h postuse. In the Washington replication sample, participants (n=39) used DRUID before acute cannabis consumption and then every half hour for 2.5 h. Results: In both studies, peak DRUID impairment effects were seen immediately after cannabis use, with recovery of performance at 1 h postuse. Specifically, significant quadratic effects of time emerged for both studies (Colorado study: (β=-0.935, SE=0.204, p<0.001); Washington study: β=3.0299, SE=1.3085, p<0.01). Domain-specific effects were tested in the larger Colorado study and were observed for reaction time within a complex divided attention task and a postural-stability balance task. Conclusions: These findings demonstrate that psychomotor impairment emerges immediately after acute cannabis use even in regular users, but decreases significantly 1 h postuse. These results underscore the potential utility of the DRUID app for assessing acute cannabis-related psychomotor impairment. Further research is needed to explore whether the DRUID app and/or the specific psychomotor functions it assesses might serve as a tool for measuring cannabis-related driving impairment. Clinical trials registration number for the Colorado Study: NCT03522103.

Impact of smoking cannabidiol (CBD)-rich marijuana on driving ability

To investigate effects of smoking cannabidiol (CBD)-rich marijuana on driving ability and determine free CBD and Δ⁹-tetrahydrocannabinol (THC) concentrations in capillary blood samples, a randomised, double-blind, placebo-controlled, two-way crossover pilot study was conducted with 33 participants. Participants smoked a joint containing 500 mg of tobacco and either 500 mg of CBD-rich marijuana (16.6% total CBD; 0.9% total THC) or 500 mg of a placebo substance, then performed three different dimensions of the Vienna Test System TRAFFIC examining reaction time, behaviour under stress, and concentration performance. For further assessment of participants' fitness to drive, three tests of balance and coordination were evaluated and vital signs (blood pressure and pulse) were measured. Dried blood spot samples of capillary blood were taken after smoking and after completion of the tests to determine the cannabinoid concentrations (CBD, THC and THC-metabolites). The results revealed no significant differences between the effects of smoking CBD-rich marijuana and placebo on reaction time, motor time, behaviour under stress, or concentration performance. Maximum free CBD and THC concentrations in capillary blood were detected shortly after smoking, ranging between 2.6-440.0 ng/mL and 6.7-102.0 ng/mL, respectively. After 45 min, capillary blood concentrations had already declined and were in the range of 1.9-135.0 ng/mL (free CBD) and 0.9-38.0 ng/mL (free THC). Although the observed levels of free THC concentrations have been reported to cause symptoms of impairment in previous studies in which THC-rich marijuana was smoked, no signs of impairment were found in the current study. This finding suggests that higher CBD concentrations cause a negative allosteric effect in the endocannabinoid system, preventing the formation of such symptoms. Nevertheless, it is recommended that consumers refrain from driving for several hours after smoking CBD-rich marijuana, as legal THC concentration limits may be exceeded. Supplemental data for this article is available online at https://doi.org/10.1080/20961790.2021.1946924 .

Female Sex as a Protective Factor in the Effects of Chronic Cannabis Use on Verbal Learning and Memory

OBJECTIVE

The variability of findings in studies examining the effects of chronic cannabis use on neuropsychological functioning highlights the importance of examining contributing factors. Few studies examine the role of sex in the relationship between cannabis and neuropsychological functioning, despite known neurobiological structural differences between males and females. This study examined whether males and females experience differential cognitive effects of chronic cannabis use.

METHOD

Chronic cannabis users (3+ days per week for >12 months, n = 110, 72% male) and non-users (n = 71, 39% male) completed a neuropsychological test battery. Two multivariate analyses of covariance (MANCOVAs) examined for sex differences in performance within users and non-users on neuropsychological tests, controlling for potential confounding variables. Bonferroni corrections were applied to adjust for multiple comparisons.

RESULTS

Male and female cannabis users did not differ in cannabis use variables. Female cannabis users performed better than males on multiple subtests of the California Verbal Learning Test-II (CVLT-II), a verbal learning and memory test. Male cannabis users performed better than female users on Trial 1 of the CVLT-II (p = .002), and Trail Making Test B (p = .001), which measure attention and cognitive flexibility, respectively. Non-user males and females performed comparably, with the exception of Trail Making Test B (p = .001).

CONCLUSIONS

Results suggest that chronic cannabis use differentially impacts males and females, with females exhibiting better verbal learning and memory despite males demonstrating better attention and cognitive flexibility. Further research is needed to understand the potential protective mechanism of female sex on learning and memory effects of cannabis use.

Assessment of cognitive and psychomotor impairment, subjective effects, and blood THC concentrations following acute administration of oral and vaporized cannabis

BACKGROUND

Cannabis legalization is expanding, but there are no established methods for detecting cannabis impairment.

AIM

Characterize the acute impairing effects of oral and vaporized cannabis using various performance tests.

METHODS

Participants (N = 20, 10 men/10 women) who were infrequent cannabis users ingested cannabis brownies (0, 10, and 25 mg Δ-9-tetrahydrocannabinol, THC) and inhaled vaporized cannabis (0, 5, and 20 mg THC) in six double-blind outpatient sessions. Cognitive/psychomotor impairment was assessed with a battery of computerized tasks sensitive to cannabis effects, a novel test (the DRiving Under the Influence of Drugs, DRUID^®), and field sobriety tests. Blood THC concentrations and subjective drug effects were evaluated.

RESULTS

Low oral/vaporized doses did not impair cognitive/psychomotor performance relative to placebo but produced positive subjective effects. High oral/vaporized doses impaired cognitive/psychomotor performance and increased positive and negative subjective effects. The DRUID^® was the most sensitive test to cannabis impairment, as it detected significant differences between placebo and active doses within both routes of administration. Women displayed more impairment on the DRUID^® than men at the high vaporized dose only. Field sobriety tests showed little sensitivity to cannabis-induced impairment. Blood THC concentrations were far lower after cannabis ingestion versus inhalation. After inhalation, blood THC concentrations typically returned to baseline well before pharmacodynamic effects subsided.

CONCLUSIONS

Standard approaches for identifying impairment due to cannabis exposure (i.e. blood THC and field sobriety tests) have severe limitations. There is a need to identify novel biomarkers of cannabis exposure and/or behavioral tests like the DRUID^® that can reliably and accurately detect cannabis impairment at the roadside and in the workplace.

Effects of chronic marijuana use on driving performance

OBJECTIVES

The effects of marijuana on driving pose a significant public health concern. More studies on chronic marijuana use in driving are needed. The study objectives were to (1) assess differences in the Standardized Field Sobriety Test (SFST) and driving performance outcomes between chronic medical marijuana users and nonusers and (2) identify a cutoff tetrahydrocannabinol (THC) concentration above which chronic medical marijuana users demonstrate driving impairment.

METHODS

This prospective cross-sectional study assessed 31 chronic marijuana users and 41 nonusers. Rapid Detect Saliva Drug Screen 10-panel was administered to all participants. Participants were given a simple visual reaction time test (SVRT) and SFST consisting of the horizontal gaze nystagmus (HGN), the one leg stand (OLS), and the walk and turn (WAT) tests. The STISIM Drive M100 driving simulator assessed driving performance. Driving parameters included standard deviation of speed (SDS), deviation of mean lane position, off-road accidents, collisions, pedestrians hit, and car-following modulus, delay, and coherence. Cannabinoid blood plasma was obtained from marijuana users.

RESULTS

Marijuana users and nonusers did not differ in age (40.06 ± 13.92 vs. 41.53 ± 15.49, P = .6782). Marijuana users were more likely to fail the SFST (P = .005) and the WAT (P = .012) and HGN (P = .001) components. Marijuana users had slower SVRT (P = .031), less SDS (P = .039), and lower modulus (P = .003). Participants with THC >2 ng/mL (P = .017) and TCH >5 ng/mL (P = .008) had lower SDS. Participants with THC >2 ng/mL (P = .021) and THC >5 ng/mL (P = .044) had decreased modulus.

CONCLUSION

Chronic marijuana users had slower reaction times, deviated less in speed, and had difficulty matching a lead vehicle's speed compared to nonusers. The effects on SDS and modulus were present at cutoffs of 2 and 5 ng/mL.

A Two-Year Study of Δ 9 Tetrahydrocannabinol Concentrations in Drivers; Part 2: Physiological Signs on Drug Recognition Expert (DRE) and non-DRE Examinations,

Whole blood samples were examined for ∆⁹ -Tetrahydrocannabinol (THC) over 2 years in drivers suspected of driving under the influence. Part one of the study examined the link between [THC] and performance on field sobriety tests. This portion examined objective signs, eye examinations and physiological indicators; and their relationship to the presence of THC. Several objective signs were excellent indicators of the presence of THC: red eyes (94%), droopy eyelids (85.6%), affected speech (87.6%), tongue coating (96.2%), and odor of marijuana (82.4%). About 63.6% of THC positive subjects had dialted pupils (room light). THC positive subjects had either rebound dilation or hippus in 88.8% of cases. Pulse and blood pressure (BP) were evaluated to determine any correlation with [THC]. An increased pulse rate correlated well to the presence of THC (88.5%), but not [THC]. BP did not correlate to [THC] and was also a poor indicator of THC in the blood (50% high).

Evaluation of divided attention psychophysical task performance and effects on pupil sizes following smoked, vaporized and oral cannabis administration

Establishing science-based driving per se blood Δ⁹ -tetrahydrocannabinol (THC) limits is challenging, in part because of prolonged THC detection in chronic, frequent users. Therefore, documenting observable signs of impairment is important for driving under the influence of drugs. We evaluated frequent and occasional cannabis smokers' performance on the modified Romberg balance, one leg stand (OLS), and walk and turn (WAT) tasks, and pupil size effects following controlled placebo (0.001% THC), smoked, vaporized and oral (6.9% [~50.4 mg] THC) cannabis administration. Significant effects following inhaled doses were not observed due to delayed tasks administration 1.5 and 3.5 h post-dose, but significant impairment was observed after oral dosing (blood THC concentrations peaked 1.5-3.5 h post-dose). Occasional smokers' odds of exhibiting ≥2 clues on the OLS or WAT following oral dosing were 6.4 (95% CI 2.3-18.4) times higher than after placebo, with THC and 11-hydroxy-THC blood concentrations individually producing odds ratios of 1.3 (1.1-1.5) and 1.5 (1.3-1.8) for impairment in these tasks, respectively. Pupil sizes after oral dosing under the direct lighting condition were significantly larger than after placebo by mean (SE, 95% CI) 0.4 (0.1, 0.2-0.6) mm at 1.5 h and 0.5 (0.2, 0.2-0.8) mm at 3.5 h among all participants. Oral cannabis administration impaired occasional cannabis users' performance on the OLS and WAT tasks compared to placebo, supporting other reports showing these tasks are sensitive to cannabis-related impairment. Occasional smokers' impairment was related to blood THC and 11-hydroxy-THC concentrations. These are important public health policy findings as consumption of edible cannabis products increases. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

A Judicial Perspective on Expert Testimony in Marijuana Driving Cases

The decriminalization of marijuana and propagation of marijuana prescribed for medical reasons have resulted in an increase in driving while under the influence of marijuana. Currently, the legal definition of marijuana driving impairment varies by state across the United States. Expert witnesses such as drug recognition experts and medical toxicologists are needed during a discovery to educate attorneys and during a testimony to educate judges and juries. These proceedings provide an overview of the US case law about driving impairment, the current status of the legal thresholds used in the courts for the admission of the medical toxicologist as an expert witness in marijuana driving and related cases, and provides an understanding of evolving issues surrounding the admissibility of their scientific opinion testimony.

Drug Recognition Expert (DRE) examination characteristics of cannabis impairment

BACKGROUND

The Drug Evaluation and Classification Program (DECP) is commonly utilized in driving under the influence (DUI) cases to help determine category(ies) of impairing drug(s) present in drivers. Cannabis, one of the categories, is associated with approximately doubled crash risk. Our objective was to determine the most reliable DECP metrics for identifying cannabis-driving impairment.

METHODS

We evaluated 302 toxicologically-confirmed (blood Δ(9)-tetrahydrocannabinol [THC] ≥1μg/L) cannabis-only DECP cases, wherein examiners successfully identified cannabis, compared to normative data (302 non-impaired individuals). Physiological measures, pupil size/light reaction, and performance on psychophysical tests (one leg stand [OLS], walk and turn [WAT], finger to nose [FTN], Modified Romberg Balance [MRB]) were included.

RESULTS

Cases significantly differed from controls (p<0.05) in pulse (increased), systolic blood pressure (elevated), and pupil size (dilated). Blood collection time after arrest significantly decreased THC concentrations; no significant differences were detected between cases with blood THC <5μg/L versus ≥5μg/L. The FTN best predicted cannabis impairment (sensitivity, specificity, positive/negative predictive value, and efficiency ≥87.1%) utilizing ≥3 misses as the deciding criterion; MRB eyelid tremors produced ≥86.1% for all diagnostic characteristics. Other strong indicators included OLS sway, ≥2 WAT clues, and pupil rebound dilation. Requiring ≥2/4 of: ≥3 FTN misses, MRB eyelid tremors, ≥2 OLS clues, and/or ≥2 WAT clues produced the best results (all characteristics ≥96.7%).

CONCLUSIONS

Blood specimens should be collected as early as possible. The frequently-debated 5μg/L blood THC per se cutoff showed limited relevance. Combined observations on psychophysical and eye exams produced the best cannabis-impairment indicators.

The Standardized Field Sobriety Tests (SFST) and measures of cognitive functioning

OBJECTIVE

The Standardized Field Sobriety Tests (SFST) are utilised widely to assess fitness to drive when law enforcement suspects a driver's ability to drive is impaired, whether by drugs or alcohol. The SFST ostensibly achieve this through assessment of the level of drivers' cognitive and psychomotor impairment, although no studies have explicitly assessed the relatedness of cognitive ability and performance on the SFST. The current study aimed to assess the relationship between the three components of the SFST with a well validated computerised cognitive battery.

METHOD

A sub-set of 61 placebo condition participants comprised the sample, with 33 females and 28 males (mean age 25.45 years). Correlations between the individual SFST subscales 'Horizontal Gaze Nystagmus' (HGN), the 'One Leg Stand' (OLS) and the 'Walk and Turn' test (WAT) and Cognitive Drug Research (CDR) sub-scales of 'Quality of Working Memory', 'Power of Attention' and 'Continuity of Attention' were analysed using point-biserial correlation.

RESULTS

Sixty participants were included for analyses. A weak-moderate positive (five subscales) and a moderate-strong negative (two subscales) association was noted between seven of the nine individual CDR subscales and the SFST subscale of the WAT test (all p<0.05). Individually, a moderate positive association was noted between the sub-scale 'Nystagmus lack of smooth pursuit' and 'digit vigilance reaction time' and 'choice reaction time; reaction time' (both p<0.05) and 'Nystagmus head move and/or jerk' and 'simple reaction time' (p<0.001). When assessed as a partially composite factor, a comparable association was also noted between the composite score of the SFST subscale 'Nystagmus head move and/or jerk' and both (a) simple and (b) digit vigilance reaction time (both p<0.05). No association was noted between any of the individual cognitive variables and the SFST subscale 'OLS', or between composite cognitive scores 'Quality of Working Memory', 'Power of Attention' and 'Continuity of Attention' and total SFST scores.

DISCUSSION

Variation in some aspects of cognitive performance was found to be moderately and positively correlated with some individual aspects of the SFST; particularly among tasks which assess reaction time. Impairment of these cognitive processes can also contribute to the completion of complex tasks such as driving or the SFST. Complex behavioural tasks such as driving are often severely impaired due to intoxication, and thus in a practical sense, the SFST can still be considered a useful screening tool to identify drug or alcohol impaired drivers.

The Effects of Dextromethorphan on Driving Performance and the Standardized Field Sobriety Test

Dextromethorphan (DXM) is abused most commonly among adolescents as a recreational drug to generate a dissociative experience. The objective of the study was to assess driving with and without DXM ingestion. The effects of one-time maximum daily doses of DXM 120 mg versus a guaifenesin 400 mg dose were compared among 40 healthy subjects using a crossover design. Subjects' ability to drive was assessed by their performance in a driving simulator (STISIM® Drive driving simulator software) and by conducting a standardized field sobriety test (SFST) administered 1-h postdrug administration. The one-time dose of DXM 120 mg did not demonstrate driving impairment on the STISIM® Drive driving simulator or increase SFST failures compared to guaifenesin 400 mg. Doses greater than the currently recommended maximum daily dose of 120 mg are necessary to perturb driving behavior.

The relationship between observed signs of impairment and THC concentration in oral fluid

BACKGROUND

Studies have shown that cannabis intake increases the risk of traffic accidents. Controlled experiments support these findings and have shown a positive dose-effect relationship.

METHODS

In this retrospective cross-sectional study of data from a roadside survey, we investigated whether a police officer's judgment regarding signs of impairment is related to the concentration of delta-9-tetrahydrocannabinol (THC) in the oral fluid (OF). We investigated 2,632 cases from a representative sample of 3,302 Spanish drivers: 253 drivers positive for THC only, 32 positive for THC and ethanol, 201 with only ethanol detected in their breath, and 2,146 drivers who tested negative for ethanol in breath and drugs in OF. Recorded data comprised breath alcohol concentrations, THC concentrations in the OF, and the 31 observed signs of impairment. Subject groups were compared using the chi-square test, and logistic regression was used to examine the risk of being categorized as exhibiting signs of impairment.

RESULTS

A relationship was found between the OF THC concentration and some observed signs of impairment. Eye signs were noticeable from a THC concentration >3.0 ng/ml in OF, and >25 ng/ml was related to behavior, facial expression, and speech signs. Alcohol and THC contribute to impairment independently and, when taken simultaneously, the effects are comparable to the sum of the effects when consumed separately.

CONCLUSIONS

The observation of signs of impairment due to cannabis occurs in an OF concentration-related manner but, as a clinical test, OF has low sensitivity and specificity in a random roadside survey.

An examination of the validity of the standardized field sobriety test in detecting drug impairment using data from the Drug Evaluation and Classification program

OBJECTIVE

The purpose of this study is to assess the validity of the 3 components of the Standardized Field Sobriety Test (SFST), including the Horizontal Gaze Nystagmus (HGN), One Leg Stand (OLS), and Walk and Turn (WAT) tests, in identifying impairment among suspected drug-impaired drivers using data recorded during drug evaluation and classification (DEC) evaluations.

METHODS

Data from 2142 completed DEC evaluations of central nervous system (CNS) stimulants, CNS depressants, narcotic analgesics, cannabis, or no drugs were analyzed using multinomial logistic regression.

RESULTS

All drug categories were significantly associated with impaired performance. On the HGN, users of CNS depressants were significantly more likely to experience lack of smooth pursuit and distinct nystagmus at maximum deviation compared to non-drug users. On the OLS, users of all drug classes were significantly more likely to sway while balancing and use their arms to maintain balance but significantly less likely to hop compared to drug-free cases. Users of CNS depressants, CNS stimulants, and narcotic analgesics were significantly more likely to put their raised foot down during the test. On the WAT, users of CNS depressants, CNS stimulants, and narcotic analgesics were significantly less likely to keep their balance while listening to test instructions compared to those who had not used drugs. Users of CNS depressants were less likely to touch heel-to-toe while walking, whereas individuals who had used narcotic analgesics were less likely to take the correct number of steps.

CONCLUSIONS

These findings provide support for the use of the SFST as a screening tool for law enforcement to identify impairment in persons who have used CNS stimulants, CNS depressants, cannabis, or narcotic analgesics.

The methodological quality of three foundational law enforcement Drug Influence Evaluation validation studies

BACKGROUND

A Drug Influence Evaluation (DIE) is a formal assessment of an impaired driving suspect, performed by a trained law enforcement officer who uses circumstantial facts, questioning, searching, and a physical exam to form an unstandardized opinion as to whether a suspect's driving was impaired by drugs. This paper first identifies the scientific studies commonly cited in American criminal trials as evidence of DIE accuracy, and second, uses the QUADAS tool to investigate whether the methodologies used by these studies allow them to correctly quantify the diagnostic accuracy of the DIEs currently administered by US law enforcement.

RESULTS

Three studies were selected for analysis. For each study, the QUADAS tool identified biases that distorted reported accuracies. The studies were subject to spectrum bias, selection bias, misclassification bias, verification bias, differential verification bias, incorporation bias, and review bias. The studies quantified DIE performance with prevalence-dependent accuracy statistics that are internally but not externally valid.

CONCLUSION

The accuracies reported by these studies do not quantify the accuracy of the DIE process now used by US law enforcement. These studies do not validate current DIE practice.

Toxicology observation: nystagmus after marijuana use

Traditional teaching has held that horizontal-gaze nystagmus is a sign of intoxication by sedatives such as alcohol but not marijuana. This is a case report of an adult male who presents with 3 days of visual disturbance and dizziness following marijuana use. The exam was notable for gaze-evoked nystagmus and ataxia. Lab testing was normal except that urine drug screening was positive for marijuana only. Imaging included computed tomography (CT) and magnetic resonance imaging (MRI) scans of the head. Prior studies showing a negative association of nystagmus with marijuana are reviewed. This case is presented as a possible exception to the generalisation that marijuana is not associated with nystagmus.

The effects of cannabis and alcohol on simulated driving: Influences of dose and experience

BACKGROUND

Cannabis and alcohol are the most popular drugs amongst recreational users, and most prevalent in injured and deceased drivers. Clarification of the interactive effects of these drugs upon driving behaviour is critical for reducing drug-related road deaths.

OBJECTIVES

The current study had two objectives, to examine the effects of cannabis and alcohol on driving performance, and identify if any differences between the effects of cannabis and alcohol on driving performance exist between regular cannabis users and non-regular cannabis users.

METHODS

The project involved 80 participants (49 male, 31 female) who were abstinent recreational users of alcohol and marijuana. They participated in six experimental sessions that involved the consumption of cannabis cigarettes containing no THC, 1.8% THC or 3% THC together with the consumption of alcohol to obtain either 0% BAC, 0.03% BAC or 0.05% BAC. The six sessions were double-blind, counter-balanced, placebo-controlled and medically supervised. Forty participants were allocated to the cannabis with low alcohol (0.03% BAC) group, and 40 participants were allocated to the cannabis with high alcohol (0.05% BAC) group. Driving simulator performance was assessed at 20min post-drug administration and blood samples were taken before and after driving.

RESULTS

Driving simulator performance was more impaired in the THC and alcohol combined conditions. Consistent with past research, the level of THC detected in blood is higher when THC is consumed with alcohol, than when cannabis is consumed alone, and regular cannabis users returned higher levels of THC in plasma than non-regular users. Generally, regular cannabis users displayed more driving errors than non-regular cannabis users.

Detecting impairment associated with cannabis with and without alcohol on the Standardized Field Sobriety Tests

RATIONALE

Cannabis and alcohol are the most popular drugs amongst recreational users and most prevalent in injured and deceased drivers. The Standardized Field Sobriety Tests (SFST) are commonly used to establish impairment due to drugs and alcohol, but limited empirical evidence exists concerning the combined effects of these drugs on SFST performance.

METHODS

The sample comprised 80 individuals (31 females; 49 males). Age ranged between 21 and 35 years (M = 26.5, SD = 5). Forty participants (15 females; 25 males) took part in the low alcohol condition (BAC, <0.05 %), and 40 participants (16 females; 24 males), took part in the high alcohol condition (BAC, >0.05 %). For each part of the study, two levels of ∆9-tetrahydrocannabinol (THC) were administered (1.8 and 3 % THC) or a matching placebo cigarette (0 % THC) in combination with alcohol. Performance on the SFST was assessed 30 min post-dosing.

RESULTS

A number of significant differences in SFST performance were identified with 28 % of the sample failing the test (when the head movement and jerks sign was included) when low alcohol and low THC were administered together. When a higher dose of alcohol was administered with a low dose of THC, 38 % of the sample failed the test, and 35 % also failed when the high dose of alcohol was combined with a higher dose of THC.

CONCLUSIONS

The current results highlight the limited ability of the SFST to identify drug consumption in the absence of any evidence of driving impairment or physiological indicators.

A placebo-controlled study to assess Standardized Field Sobriety Tests performance during alcohol and cannabis intoxication in heavy cannabis users and accuracy of point of collection testing devices for detecting THC in oral fluid

RATIONALE

Standardized Field Sobriety Tests (SFST) and oral fluid devices are used to screen for driving impairment and roadside drug detection, respectively. SFST have been validated for alcohol, but their sensitivity to impairment induced by other drugs is relatively unknown. The sensitivity and specificity for Δ(9)-tetrahydrocannabinol (THC) of most oral fluid devices have been low.

OBJECTIVE

This study assessed the effects of smoking cannabis with and without alcohol on SFST performance. Presence of THC in oral fluid was examined with two devices (Dräger Drug Test® 5000 and Securetec Drugwipe® 5).

METHODS

Twenty heavy cannabis users (15 males and 5 females; mean age, 24.3 years) participated in a double-blind, placebo-controlled study assessing percentage of impaired individuals on the SFST and the sensitivity of two oral fluid devices. Participants received alcohol doses or alcohol placebo in combination with 400 μg/kg body weight THC. We aimed to reach peak blood alcohol concentration values of 0.5 and 0.7 mg/mL.

RESULTS

Cannabis was significantly related to performance on the one-leg stand (p = 0.037). Alcohol in combination with cannabis was significantly related to impairment on horizontal gaze nystagmus (p = 0.029). The Dräger Drug Test® 5000 demonstrated a high sensitivity for THC, whereas the sensitivity of the Securetec Drugwipe® 5 was low.

CONCLUSIONS

SFST were mildly sensitive to impairment from cannabis in heavy users. Lack of sensitivity might be attributed to tolerance and time of testing. SFST were sensitive to both doses of alcohol. The Dräger Drug Test® 5000 appears to be a promising tool for detecting THC in oral fluid as far as correct THC detection is concerned.

Medicinal Δ(9) -tetrahydrocannabinol (dronabinol) impairs on-the-road driving performance of occasional and heavy cannabis users but is not detected in Standard Field Sobriety Tests

AIMS

The acute and chronic effects of dronabinol [medicinal Δ(9) -tetrahydrocannabinol (THC)] on actual driving performance and the Standard Field Sobriety Test (SFST) were assessed. It was hypothesized that occasional users would be impaired on these tests and that heavy users would show less impairment due to tolerance.

DESIGN, SETTING AND PARTICIPANTS

Double-blind, placebo-controlled, randomized, three-way cross-over study. Twelve occasional and 12 heavy cannabis users (14 males/10 females) received single doses of placebo, 10 and 20 mg dronabinol.

MEASUREMENTS

Standard deviation of lateral position (SDLP; i.e. weaving) is the primary measure of road-tracking control. Time to speed adaptation (TSA) is the primary reaction-time measure in the car-following test. Percentage of impaired individuals on the SFST and subjective high on a visual analogue scale were secondary measures.

FINDINGS

Superiority tests showed that SDLP (P = 0.008) and TSA (P = 0.011) increased after dronabinol in occasional users. Equivalence tests demonstrated that dronabinol-induced increments in SDLP were bigger than impairment associated with BAC of 0.5 mg/ml in occasional and heavy users, although the magnitude of driving impairment was generally less in heavy users. The SFST did not discriminate between conditions. Levels of subjective high were comparable in occasional and heavy users.

CONCLUSIONS

Dronabinol (medicinal tetrahydrocannabinol) impairs driving performance in occasional and heavy users in a dose-dependent way, but to a lesser degree in heavy users due possibly to tolerance. The Standard Field Sobriety Test is not sensitive to clinically relevant driving impairment caused by oral tetrahydrocannabinol.

The acute effects of 3,4-methylenedioxymethamphetamine and methamphetamine on driving: a simulator study

OBJECTIVES

Illicit drugs such as MDMA and methamphetamine are commonly abused drugs that have also been observed to be prevalent in drivers injured in road accidents. Their exact effect on driving and driving behavior has yet to be thoroughly investigated.

METHODS

Sixty-one abstinent recreational users of illicit drugs comprised the participant sample, with 33 females and 28 males, mean age 25.45 years. The three testing sessions involved oral consumption of 100 mg MDMA, 0.42 mg/kg methamphetamine, or a matching placebo. The drug administration was counter-balanced, double-blind, and medically supervised. At each session driving performance was assessed 3 h and 24 h post drug administration on a computerized driving simulator.

RESULTS

At peak concentration overall impairment scores for driving (F(2,118)=9.042, p<0.001) and signaling (F(2,118)=4.060, p=0.020) were significantly different for the daytime simulations. Performance in the MDMA condition was worse than both the methamphetamine (p=0.023) and placebo (p<0.001) conditions and the methamphetamine condition was also observed to be worse in comparison to the placebo (p=0.055). For signaling adherence, poorer signaling adherence occurred in both the methamphetamine (p=0.006) and MDMA (p=0.017) conditions in comparison to placebo in the daytime simulations.

CONCLUSIONS

The findings of this study have for the first time illustrated how both MDMA and methamphetamine effect driving performance, and provide support for legislation regarding testing for the presence of illicit drugs in impaired or injured drivers as deterrents for driving under the influence of illicit drugs.

The effect of d-methamphetamine on simulated driving performance

OBJECTIVES

Methamphetamine is considered to be one of the most popularly abused drugs by drivers; however, its exact effect on driving and driving behaviour has yet to be thoroughly investigated. This being despite methamphetamine's increased prevalence in injured and deceased drivers.

METHODS

Twenty healthy recreational illicit stimulant users (10 male and 10 female), aged between 21 and 32 years (mean = 25.4 years, SD = 3.3 years) attended two testing sessions involving oral consumption of 0.42 mg/kg d-methamphetamine or a matching placebo. The drug administration was counter-balanced, double-blind, and medically supervised. At each session driving, performance was assessed 2.5 h post drug administration.

RESULTS

d-methamphetamine (0.42 mg/kg) did not significantly impair overall simulated driving performance 2.5 h post drug administration. At the individual driving variable level, participants in the d-methamphetamine condition were observed to be driving slower when an emergency situation occurred (T = 44, p < 0.05), but interestingly, participants in both conditions recorded average speeds in excess of the speed limit (100 km/h) when the emergency situations occurred. The d-methamphetamine condition did also produce four times more infringements where participants did not stop at red traffic light in comparison to the placebo, but this effect was only evident at a trend level (T = 7, p = 0.11).

CONCLUSIONS

The findings presented herein suggest that d-methamphetamine administered at the levels supplied did not impair driving performance in a manner consistent with epidemiological evidence. Further research is certainly required to elucidate the effects of various doses of methamphetamine, alone and in combination with other legal and illicit substances.

The effect of d,l-methamphetamine on simulated driving performance

RATIONALE

Illicit drugs such as methamphetamine are commonly abused drugs that have also been observed to be prevalent in drivers injured in road accidents. The exact effect of methamphetamine or its specific isomers on driving and driving behaviour have yet to be thoroughly investigated.

METHODS

Twenty healthy recreational illicit stimulant users (ten males, ten females), aged between 21 and 34 years (mean = 24.3 years, SD = 3.4 years), attended two testing sessions involving oral consumption of 0.42 mg/kg d,l-methamphetamine or a matching placebo. The drug administration was counterbalanced, double-blind, and medically supervised. At each session, driving performance was assessed 2.5 h post-drug administration.

RESULTS

Mean blood and saliva d,l-methamphetamine concentrations of approximately 90 and 400 ng/ml, respectively, at 2 h and 95 and 475 ng/ml at 3 h were observed. These levels of d,l-methamphetamine were found not to significantly impair, or improve, driving performance at the 2.5-h post-drug administration time point.

CONCLUSIONS

The findings of this study illustrate that d,l-methamphetamine has no significant effect on simulated driving performance.

Gender moderates the impact of stereotype threat on cognitive function in cannabis users

Research reveals mixed results for the effects of cannabis on cognitive functioning. These divergent results might stem from stereotype threat (ST), which occurs when individuals believe that a group to which they belong is inferior, resulting in poor test performance. Widespread media coverage of purported cannabis-related deficits in cognitive functioning may elicit ST among cannabis users, particularly among men, who may be more likely than women to identify with the cannabis-user stereotype. To investigate this hypothesis, cannabis users (30 male, 27 female) read a summary of research indicating either that cannabis produced deficits (ST condition), or that cannabis actually created no changes in cognitive functions. Participants then completed cognitive tests. Examination of the gender x condition interaction revealed significant results on 4 tests: the California Verbal Learning Test-II immediate recall task, the Controlled Oral Word Association Test for number of words generated and number of switches between clusters, and the Digit Symbol Substitution Task. Males exposed to ST performed worse on all tests compared to men not exposed to ST, while women exposed to ST performed better than women not exposed. These results suggest that cognitive deficits observed in male cannabis users may be attributed to ST rather than decreased functioning. Surprisingly, women in the ST condition scored higher than controls. Perhaps female users do not identify with the typical cannabis stereotype. This study highlights the importance of disconfirming relevant stereotypes prior to examination of the cognitive abilities of cannabis users.

Impairment due to cannabis and ethanol: clinical signs and additive effects

AIMS

Studies have shown that the impairing effects of Delta-9-tetrahydrocannabinol (THC) are dose-related. Cannabis intake increases the risk of traffic accidents. The purpose of this study was to see how different clinical tests and observations were related to blood THC concentrations and to determine whether the combined influence of THC and ethanol was different from either drug alone.

DESIGN

A retrospective cross-sectional forensic database study.

SETTING

Drivers apprehended by the police suspected of driving under the influence of alcohol and other drugs.

PARTICIPANTS

We investigated 589 cases positive for THC only. In addition, 894 cases with THC and ethanol were included. A comparison was made with 3480 drivers with only ethanol in their blood and 79 drivers who tested negative.

MEASUREMENTS

Data were analytical results of blood samples and the 27 clinical tests and observations included in the Norwegian clinical test for impairment (CTI).

FINDINGS

No relationship was found between blood THC concentration and most of the CTI tests. Blood THC concentration was, however, related to conjunctival injection, pupil dilation and reaction to light and to the overall risk of being judged impaired. When THC and ethanol were detected together the risk of being judged impaired was increased markedly.

CONCLUSIONS

This study demonstrates that cannabis impairs driving ability in a concentration-related manner. The effect is smaller than for ethanol. The effect of ethanol and cannabis taken simultaneously is additive. Conjunctival injection, dilated pupils and slow pupil reaction are among the few signs to reveal THC influence.

Implications of plasma Delta9-tetrahydrocannabinol, 11-hydroxy-THC, and 11-nor-9-carboxy-THC concentrations in chronic cannabis smokers

Delta(9)-Tetrahydrocannabinol (THC) is commonly found in toxicological specimens from driving under the influence and accident investigations. Plasma cannabinoid concentrations were determined in 18 long-term heavy cannabis smokers residing on an in-patient research unit for seven days of monitored abstinence. THC, 11-hydroxy-THC, and 11-nor-9-carboxy-THC (THCCOOH) were quantified by two-dimensional gas chromatography-mass spectrometry with cryofocusing. THC concentrations were > 1 ng/mL in nine (50.0%) participants (1.2-5.5 ng/mL) on abstinence day 7. THCCOOH was detected (2.8-45.6 ng/mL) in all participants on study day 7. THC and THCCOOH median percent concentration decreases (n = 18) were 39.5% and 72.9% from day 1 to 7, respectively. Most (88.9%) of the participants had at least one specimen with increased THC compared to the previous day. Cannabis use duration and plasma THCCOOH concentrations were positively correlated on days 1-3 (R = 0.584-0.610; p = 0.007-0.011). There were no significant correlations between THC concentrations > 0.25 ng/mL and body mass index on days 1-7 (R = -0.234-0.092; p = 0.350-0.766). Measurable THC concentrations after seven days of abstinence indicate a potential mechanism for residual neurocognitive impairment observed in chronic cannabis users. THC's presence in plasma for seven days of abstinence suggests its detection may not indicate recent use in daily cannabis users.

The Victorian legislative framework for the random testing drivers at the roadside for the presence of illicit drugs: an evaluation of the characteristics of drivers detected from 2004 to 2006

In December 2004, a new legislative framework for the random drug screening of drivers modeled on the successful random alcohol screening methodology came into force in Victoria, Australia. The new framework prohibits driving while methamphetamine (MA), 3,4-methylenedioxymethamphetamine (MDMA), and cannabis, delta-9-tetrahydrocannabinol (THC), are present at any level in a driver's specimen. This is enforced by police who have the legislative authority to randomly drug test drivers for the presence of MA, MDMA, and THC by oral fluid (saliva) sample screening at the roadside. This article outlines the new random drug testing legislative framework and the drug testing procedures currently in place in Victoria. This article also examines the data collected through the operation of the framework for the first two years since implementation in Victoria (December 2004-December 2006).

The Standardized Field Sobriety Tests: a review of scientific and legal issues

This article details the history and development of the National Highway and Safety Administration's Standardized Field Sobriety Tests. They are reviewed in terms of relevant scientific, psychometric, and legal issues. It is concluded that the research that supports their use is limited, important confounding variables have not been thoroughly studied, reliability is mediocre, and that their developers and prosecution-oriented publications have oversold the tests. Further, case law since their development has severed the tests from their validation data, so that they are not admissible on the criterion for which they were validated (blood alcohol concentration), and admissible for a criterion for which they were not (mental, physical, or driving impairment). Directions for further research are presented.

The relation between the blood benzodiazepine concentration and performance in suspected impaired drivers

Several experimental studies have shown a negative influence of benzodiazepines on driving skills. The objective of this study is to study the relationship between the blood concentration of benzodiazepines and the influence on performance in field sobriety tests. A retrospective case file evaluation was conducted to select cases of drivers, tested positive for benzodiazepines only in the period from January 1999 to December 2004. Drivers were grouped into the categories sub therapeutic, therapeutic or elevated concentrations. The outcome of the tests (walking, walking after turn, nystagmus, Romberg's test, behavior, pupils and orientation) was binomial. A Chi square test was used to assess differences in proportions of the categorized cases. In total 171 cases were included. Observations of behavior (n=137; p<0.01), walking (n=109; p<0.01), walking after turn (n=89; p=0.02) and Romberg's test (n=88; p<0.05) were significantly related to the benzodiazepine concentration. There was no significant relation between benzodiazepine concentration and effect on pupil size, nystagmus or orientation. The results of our study indicate a relation between the concentration of benzodiazepines and the results of some performance tests. More effort is needed to standardize the tests and to determine the sensitivity and selectivity of the tests for benzodiazepines.

Researching the intoxicated: informed consent implications for alcohol and drug research

This article considers the informed consent process in relation to carrying out research with intoxicated participants in 'field' research settings. There is little discussion in the literature of the potential problems that the intoxication of research participants may pose to research. Intoxication is a potential problem for all researchers but is heightened in field research that takes place in settings where participants are likely to be intoxicated, such as licensed venues, in drug consumption rooms, or police custody suites. The risks to research participants that intoxication poses should not be resolved by electing not to do research with intoxicated participants; it is argued that these risks can be managed to some extent, and are offset by the benefits of such research. Moreover, intoxication (and the impairment of cognitive functions relevant to valid informed consent) may not always be identifiable through behavioural or biochemical methods of detection. The search for accurate and field-practical methods for identifying intoxication amongst participants is useful, but not the only strategy for researchers who want to ensure the validity of the consent process. Suggestions are provided for devising research protocols that acknowledge and accept intoxication of research participants and attempt to protect them. One solution is to side-step identification of intoxication per se as a strategic objective in the consent process, and turn instead to established methods for ensuring that information has been understood by potential research participants.

The Victorian legislative framework for testing drivers for impairment caused by drugs other than alcohol: an evaluation of the characteristics of drivers detected from 2000 to 2005

On December 1, 2000, new legislation came into force in Victoria, Australia, that involved a framework for the procedure to be followed by the police for the detection of drivers impaired by drugs other than alcohol. An integral part of the procedure is the use of performance tests known as the standardized field sobriety tests (SFSTs) and the analysis of blood samples for the presence of drugs other than alcohol. This paper outlines the new legislative framework and the drug impairment detection procedures currently in place in Victoria. This paper also evaluates the data collected using the framework for the first five years since implementation in Victoria.

Roadside sobriety tests and attitudes toward a regulated cannabis market

Background

Many argue that prohibition creates more troubles than alternative policies, but fewer than half of American voters support a taxed and regulated market for cannabis. Some oppose a regulated market because of concerns about driving after smoking cannabis. Although a roadside sobriety test for impairment exists, few voters know about it. The widespread use of a roadside sobriety test that could detect recent cannabis use might lead some voters who currently oppose a regulated market to support it. In contrast, a question that primes respondents about the potential for driving after cannabis use might lead respondents to be less likely to support a regulated market.

Methods

Phone interviews with a national sample of 1002 registered voters asked about support for a regulated cannabis market and support for such a market if a reliable roadside sobriety test were widely available.

Results

In this sample of registered voters, 36% supported a regulated cannabis market. Exploratory chi-square tests revealed significantly higher support among men and Caucasians but no link to age or education. These demographic variables covaried significantly. Logistic regression revealed that gender, ethnicity, and political party were significant when all predictors were included. Support increased significantly with a reliable roadside sobriety test to 44%, but some respondents who had agreed to the regulated market no longer agreed when the sobriety test was mentioned. Logistic regression revealed that ethnicity and political affiliation were again significant predictors of support with a reliable sobriety test, but gender was no longer significant. None of these demographic variables could identify who would change their votes in response to the reliable roadside test.

Conclusion

Increased awareness and use of roadside sobriety tests that detect recent cannabis use could increase support for a regulated cannabis market. Identifying concerns of voters who are not Caucasian or Democrats could help alter cannabis policy.

The relationship between performance on the standardised field sobriety tests, driving performance and the level of Δ9-tetrahydrocannabinol (THC) in blood

The consumption of Delta9-tetrahydrocannabinol (THC) as cannabis has been shown to result in impaired and culpable driving. Testing drivers for the presence of THC in blood is problematic as THC and its metabolites may remain in the blood for several days following its consumption, even though the drug may no longer have an influence on driving performance. In the present study, the aim was to assess whether performance on the standardised field sobriety tests (SFSTs) provides a sensitive measure of impaired driving behaviour following the consumption of THC. In a repeated measures design, 40 participants consumed cigarettes that contained either 0% THC (placebo), 1.74% THC (low dose) or 2.93% THC (high dose). For each condition, after smoking a cigarette, participants performed the SFSTs on three occasions (5, 55 and 105 min after the smoking procedure had been completed) as well as a simulated driving test on two occasions (30 and 80 min after the smoking procedure had been completed). The results revealed that driving performance was not significantly impaired 30 min after the consumption of THC but was significantly impaired 80 min after the consumption of THC in both the low and high dose conditions. The percentage of participants whose driving performance was correctly classified as either impaired or not impaired based on the SFSTs ranged between 65.8 and 76.3%, across the two THC conditions. The results suggest that performance on the SFSTs provides a moderate predictor of driving impairment following the consumption of THC and as such, the SFSTs may provide an appropriate screening tool for authorities that wish to assess the driving capabilities of individuals suspected of being under the influence of a drug other than alcohol.

An evaluation of the sensitivity of the standardised field sobriety tests to detect the presence of amphetamine

RATIONALE

The Standardised Field Sobriety Tests (SFSTs), designed and validated to assess impairment associated with alcohol intoxication, are currently being employed by the Victoria Police (Australia) for the identification of driving impairment associated with drugs other than alcohol.

OBJECTIVES

The aim of this study was to evaluate whether the SFSTs are a sensitive measure for identifying the presence of dexamphetamine and methamphetamine.

METHODS

Three studies each employed a repeated-measures, counterbalanced, double-blind placebo-controlled design. In each study, 20 healthy volunteers completed two treatment conditions: either 0.42 mg/kg d,l-dexamphetamine and placebo, 0.42 mg/kg d,l-methamphetamine and placebo, or 0.42 mg/kg d-methamphetamine and placebo. Performance was assessed using the SFSTs, consisting of the Horizontal Gaze Nystagmus test, the Walk and Turn test, and the One Leg Stand test. Blood and saliva samples were obtained before and immediately after the administration of the SFSTs (120 and 170 min post drug administration).

RESULTS

At 120 and 170 min post drug administration, d,l-dexamphetamine blood levels were 83.16 and 98.42 ng/ml, respectively; d,l-methamphetamine levels were 90 and 95 ng/ml, respectively; and d-methamphetamine blood levels were 72 and 67 ng/ml, respectively. None of the three amphetamine doses impaired performance on the SFSTs. Using the SFSTs, the presence of dexamphetamine was identified in 5% of cases, d-methamphetamine in 5%, and d,l-methamphetamine in 0% of cases.

CONCLUSIONS

Under these conditions, the SFSTs are not a sensitive measure for detecting the presence of low levels of amphetamine.