I'd like to inject some data into this discussion.
For the article on risk taking and helmet wearing, let me please inform you all of the actual experiment performed:
The participants were told they were involved in an eye-tracking study, and they either mounted the fake eye-tracking equipment on a helmet or a cap.
Anxiety was measured using a validate questionnaire on acute anxiety.
Sensation-seeking was measured with a different questionnaire.
Risk-taking was determined by having the participants "inflate" a computer animation of a balloon and basically seeing how much they inflated it, knowing it could pop and they lose all their points. It did not involve any bicycling, simulated bicycling or questions regarding bicycling.
Results:
The difference in the risk-taking score was 40.4 with a helmet vs 31.1 with a cap, on a 100-point scale. p=0.01.
There was no relationship between risk taking and gender (p = .66), [self-reported] bicycling experience ( p = .27), and [self-reported] extent of helmet use when bicycling ( p = .60).
The authors also note in their discussion:
"Our findings initially appear different from those of some other studies. Fyhri and Phillips (2013; Phillips et al., 2011) found that risk taking in downhill bicycling,
measured through riding speed, did not simply increase when a helmet was worn; rather, the people who normally cycled with a helmet took fewer risks
when riding without one."
In that study, the authors found that routine helmet wearers slowed down when not wearing a helmet, but also reported increased anxiety. Routine non-wearers had no difference in speed or anxiety. Essentially all they demonstrated was that people who normally wear helmets don't like bicycling without a helmet.
So - neither study demonstrates decreased safety as a result of wearing helmets. The first study has limited validity to anything related to actually bicycling. The second demonstrated increased anxiety in helmet-wearers if they don't have them on.
Evidence for helmet safety:There is a meta-analysis regarding bicycle helmet safety. This was a Cochrane Collaborative meta-analysis, considered one of the best groups for reviewing medical studies. Their reports are conducted by experts in the field in question, undergo rigorous statistical review by independent parties, and are generally cited in major evidence-based guidelines by professional medical societies.
https://www.ncbi.nlm.nih.gov/pubmed/10796827Their main conclusions:
"No randomized controlled trials were found. This review identified five well conducted case control studies which met our selection criteria. Helmets provide a 63%-88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists. Helmets provide equal levels of protection for crashes involving motor vehicles (69%) and crashes from all other causes (68%). Injuries to the upper and mid facial areas are reduced 65%."
Another meta-analysis was again performed in 2018.
https://www.ncbi.nlm.nih.gov/pubmed/29677686This included some more studies because their inclusion criteria were less strict, but found the same findings.
"179 effect estimates from 55 studies from 1989-2017 are included in the meta-analysis. The use of bicycle helmets was found to reduce head injury by 48%, serious head injury by 60%, traumatic brain injury by 53%, face injury by 23%, and the total number of killed or seriously injured cyclists by 34%. Bicycle helmets were not found to have any statistically significant effect on cervical spine injury. "
Now for some anecdoteHaving taken care of many trauma patients during my training, I can tell you that relatively few bicyclists suffer major trauma (much higher for motorcyclists. However, those who do tend to have been hit by cars, and generally the cause of death is from traumatic brain injury. We are very good at fixing almost all other blunt injuries from moderate-speed collisions, but if your brain is severely injured there's essentially nothing that we can do. Either it recovers or it doesn't. Either you walk and talk again or you don't. The current evidence indicates that helmet wearing does reduce this specific form of injury. There is a fraction of people who suffer severe enough collisions that they would have died regardless, and that sucks. It does not take away from the fact that even low-impact head injuries can have serious consequences. If we had that attitude, we'd say fuck airbags, seatbelts, and hell metal cars. Let's drive around in paper-mache crotch rockets and have fun!
I personally don't give a damn if anyone other than my friends or family members wear a helmet, and especially don't care about people who purposefully refuses to wear them (since I don't do trauma anymore! Hooray!) I sure got sick of explaining to patients' families why their loved one is never going to wake up. So if you don't, please write a letter so it can be given to your family members in the event of your permanent neurologic disability and/or death. Thanks!