A significant proportion of drivers using drugs or medicines is probably not fully aware of the possible risks. Research shows that information on this subject does not reach everyone, or it is not read or understood by everyone.
A review of several European studies on risk information and education about drugs/medicines showed that 50 to 80% of the patients had received risk information ((package) leaflets). Of all patients that had received the information, 90% had read the leaflets. But, in a knowledge test, not even 40% of the questions was correctly answered by a majority (> 60%) [40]. Similar figures were found in Dutch research: 56% of the users had received some information, 86% of them had read the information entirely and 30% had correctly answered all knowledge questions [41].
Dutch research among younger users of drugs and impairing medicines shows that knowledge and awareness about risks are present to a certain extent, but are far from complete. In the Netherlands, a proportion of young people are indeed aware of the general and personal dangers involved in driving under the influence of drugs. A 2018 questionnaire among 361 young drivers (aged 18-24) showed that 63% agreed with the statement that crash risk is higher after drug use and 53% with the statement that they are themselves behaving dangerously when using drugs in traffic [42]. The need for better information and more knowledge about drugs is also felt: 60% of the young participants indicated they would like to have more information about drug safety; 49% would like more information about the risk of drug use in traffic [42].
More knowledge about the dangers of drugs and medicines is a prerequisite for changing one’s own attitude or behaviour, but it is insufficient in itself. Several studies show that people systematically overestimate their own abilities to drive safely. They do not realise that drugs and medicines may be just as dangerous as alcohol and that the effects are greater when combined substances are used [43]. In this respect, optimism bias may be relevant: in general, people think they run fewer risks than others [44].Consequently, risk information in package leaflets of medicines may be considered relevant to others, but not to themselves [45] [46]. Research shows that even when patients are informed about adverse side effects of impairing medicines, more than half of them do not adapt their driving behaviour. Research also shows that experience with medicine use may even lead to reduced risk assessment [41] [47]. The effect of information and education may be short-lived and may quickly fade. In France, the introduction of pictograms concerning the danger of medicines led to adaptation of medicine users’ driving behaviour shortly after the introduction, thereby reducing the risk of causing a crash. Over time, however, this risk increased again [48].
