In a new article published in Psychopharmacology, Anne Vingaard Olesen and her colleagues explore the correlation between psychotropic drug use and car accidents. Cognitive impairment is an effect of many commonly prescribed psychotropic drugs and a common cause of car accidents. The authors investigated psychotropic drug use and car accidents by comparing data from 130,000 people involved in car accidents to prescription data from Denmark between 1996 and 2018. The present research concludes that using cognitively impairing drugs positively correlates with involvement in car accidents.
The authors suggest that while it may seem tempting to ban psychotropic medication while operating a motor vehicle, this may not be a viable or fair solution. While there does seem to be a link between psychotropic drugs and car accidents, the authors remind us that we accept the increased risk of traffic accidents from many groups, including young drivers and the physically disabled. They write:
“The study shows that the use of psychotropic medication is associated with an increased risk of traffic crashes, but whether these results should lead to driving bans is, as in many other situations in road traffic, a political trade-off between the risk of crashes and mobility.”
Many commonly prescribed psychotropic drugs cause cognitive impairment. For example, researchers have found that long-term Benzodiazepine use impairs cognitive function. Moreover, this impaired cognition likely remains even after withdrawing from the drug.
Research has found that anticholinergic medications (many antidepressants and antipsychotics) are linked to cognitive impairment in service users diagnosed with schizophrenia. These medications are also linked to cognitive decline, particularly in people at risk for Alzheimer’s. Similarly, antipsychotics are positively correlated with cognitive and memory impairments.
A study of antidepressant use in postmenopausal women found a 70% increased risk of cognitive impairment in women using antidepressant drugs. These drugs have also been linked to the development of dementia. In addition, research has also found that antidepressant medications are linked to cognitive impairment in otherwise healthy subjects.
Many people prescribed psychotropic medications take more than one at a time; a practice called polypharmacy. Research has found that polypharmacy is common in psychiatry, with prevalence rates between 13%-90%. Research has also found that polypharmacy can lead to cognitive impairment.
While some champions of psychotropic medication have suggested that it is a mental illness rather than the drugs causing cognitive impairment, research has found that antidepressants are linked to cognitive impairment in healthy subjects. Other researchers have suggested that the cognitive impairments associated with schizophrenia may be due mainly to factors such as medications, motivation, and stigma.
The current work begins by explaining that many people that use psychotropic drugs also drive automobiles. Exploratory studies have found between 67% – 89% of people taking psychotropic drugs have a driver’s license, with between 77% and 92% of license holders driving regularly. As many of these drugs impair cognition, the current study aims to quantify the risk of car crashes in people using psychotropic drugs.
The researchers collected crash and prescription data of 130,000 people involved in car crashes resulting in personal injury. To be included in the study, the driver had to have a Danish civil registration number and be old enough to hold a driver’s license. The researchers examined both single-car crashes (where the responsibility for the accident was clear) and crash involving two or more automobiles.
The risk of any traffic accident causing personal injury was 24% higher for psychotropic drug users than non-users. For single car accidents, the increased risk was 117% for psychotropic drug users.
Antipsychotics showed a 14% decrease in the risk of any traffic accident with a 29% increase in the risk of a single car accident. Antidepressants and benzodiazepines showed a 30% increase in the risk of traffic accidents, with a 125% and 149% increase in the risk of single car accidents, respectively. The use of stimulants was associated with a 62% increase in the risk of traffic accidents, with the risk of single car accidents doubled compared to non-users.
Most of the individual drugs the researchers analyzed were associated with an increased risk of traffic accidents of 30% or less. For example, Zolpidem, venlafaxine, nitrazepam, escitalopram, and mianserin were associated with a 50% increase in the risk of traffic accidents. Chlordiazepoxide showed a 74% increase in traffic accident risk, and methylphenidate showed a 67% increase.
The authors note that the discrepancy between single car accidents and multiple car accident risks in psychotropic drug users is significant, with psychotropic drug users only slightly more likely to be involved in numerous car accidents but almost twice as likely to be involved in single car accidents. The authors suggest this discrepancy may be due to the low number of single car accidents used in the study (only 13.5% of the crashes were single car accidents). Another possible explanation suggested by the authors for the increased risk of single-car crashes is that they resulted from suicide attempts.
The authors found that antipsychotics were protective against crash risk, with users showing a 14% decreased risk of traffic accidents compared to non-users. However, this was not in line with the 29% increase in single car accidents for users of the same drugs. The authors suggest that this anomaly could be due to driving prohibition and refraining among users of antipsychotics. As a result, these individuals drive at a lower rate than their non-drug-using counterparts.
The authors also note that some of the increased risks of traffic accidents could result from the underlying disease or presenting symptoms rather than the drugs used to treat it.
Olesen, A. V., Madsen, T. K., Lahrmann, H., & Nielsen, J. (2022). Use of psychotropic medication and risk of Road Traffic Crashes: A registry-based case–Control Study in Denmark, 1996–2018. Psychopharmacology, 239(8), 2537–2546. https://doi.org/10.1007/s00213-022-06146- (Link)