CHRONIC CANNABIS CONSUMPTION IMPAIRS PERFORMANCE ABILITY
In addition to alcohol, the use of drugs such as cannabis when driving is increasingly posing a problem. International studies show that the extent to which a person consumes cannabis correlates with driving under the influence of this substance and risky driving behavior. There are a number of sociodemographic traits that have been proven to be strongly linked to driving after cannabis consumption – for example young men between the ages of 20 and 25 who had learning difficulties in school (evident from poor academic performance and truancy in school), coming from a single-parent family, or having previously committed several traffic offenses. The main psychosocial factors that can help predict whether someone will drive under the influence of cannabis include a poor state of health, sensation-seeking tendencies, a poor ability to exercise self-control, a personality with a high affinity to risk, as well as aggressive tendencies. All of these are personality traits also exhibited by motorists who commit alcohol-related offenses, unlike those who do not.
For Germany, there are not yet any official statistics on accident numbers, criminal offenses, or administrative offenses in connection with cannabis. For this reason, extracts from available datasets have had to suffice. Out of 1,487 blood samples taken following traffic checks in 2014 in the south and west of Saxony, 39 percent were found to contain cannabis. During the mandated blood tests as part of the medical review for gathering evidence, substance-related behavioral problems and uncertainties could only be established to a limited extent and only rarely. The results are in the low two-figure percentage range – for example problems when walking straight ahead 16.2 percent, turning around 16.5 percent, finger-to-finger test 11.1 percent, finger-to-nose test 10.0 percent, and speech 6.1 percent.
As various studies show, cannabis consumption begins between the ages of 13 and 14 with consumption rates monotonically increasing up to 19 years of age. The highest risk period for firsttime consumption, i.e., the age range when most cannabis users start using cannabis, is between 16 and 18. However, starting drug consumption from an early age (under 15) is considered a significant risk factor for causing later health, social, and emotional disorders, as the physical development of teenagers is not complete at this stage and the drugs seriously disrupt the psychosocial maturation process during puberty. The following factors, among others, play a role in causing young people to continue with their drug consumption beyond the initial try-out stage: anticipated effects, encouragement through social ties to peer group, observing positive effects of drug consumption in others, as well as having experienced subjectively positive pharmacological effects of the psychoactive substance. These experiences cause the development of states such as excitation or calm, relaxation, euphoria, or experiences being intoxicated, which can encourage future cannabis consumption and maintain it on a continual basis.
The consequences of chronic cannabis consumption are multifaceted and can affect people’s willingness and ability to perform. It can impair all of the same cognitive processes that are affected after acute intoxication: concentration, attention level, response capacity, short-term memory and working memory, psychomotor skills/abilities, as well as perception of time and space. In terms of performance willingness, apathy as well as loss of drive, motivation and interest have a negative impact on a person’s cognitive ability to control their actions, and thus on the execution of the driving task.
On the basis of unknown individual genetic dispositions, cannabis can also trigger psychological problems, such as anxiety, depression, or hallucinations, through to fully formed psychiatric disorders, such as mania or a psychotic illness. For this reason, there are certainly good reasons for setting the limit for tetrahydrocannabinol (THC) consumption as low as possible. In Germany for example, the limit is 1.0 nanograms per milliliter of blood serum, which currently constitutes the threshold for an administrative offense. It also marks the point at which a person’s fitness to drive a motor vehicle is called into question and requires evaluation, as it is not possible to exclude for certain the possibility of driving safety being impaired.
By way of comparison, in Europe several countries such as France, Great Britain, the Netherlands, Norway, Portugal, Slovenia, Spain, Sweden, and the Czech Republic have also set THC thresholds. These thresholds range quite substantially between 0.0 and 6.0 nanograms per milliliter of blood serum. The limits set in the states of the USA also vary considerably, ranging between 0 nanograms per milliliters of blood serum, such as in Arizona, Georgia, and Virginia, and 10 nanograms in Maine and Washington state.