I've always been a proponent of wearing helmets. Our noggins embody a lot of valuable stuff. I had generally stopped my thinking though at "wearing one all the time" on a bike. Witnessing the different looking POC helmets, or watching NFL/NHL debates didn't spark additional thinking. Cycling doesn't have the repetitive hits those sports do, but it does have the potential for large impacts.
I've now had the opportunity to read Bicycling Magazine's June 2013 article on this. Great job. It still is journalism, and even if its investigative, doesn't give me the perspective of a brain engineer (ha ha) on the subject. I respect copyright, but if ever an article should be freeware for the benefit of humans, this would be a good one. Get your hands on a copy, or find it online. I'll summarize some points.
The good thing is - bicycle use, trips, and commuter traffic is all increasing on decade long statistical measures, while death and injury isn't increasing at the pace of growth. Great.
Helmets you buy in bike stores meet legal standards. Those standards haven't changed in a long time. They are focused on perpendicular, linear, single shocks. That's good. It prevents your skull from cracking.
Skulls cracking and severity of concussion, which is in some ways worse and longer debilitating, isn't really correlated. Nothing in current helmet design really is designed to reduce concussive injury.
The highest liklihood of concussion involves rotational stresses, vs. direct impacts. Heads at the end of a spine is like a flap at the end of a flyswatter - whippy and acceleration prone. Woodpeckers don't get concussions, and on slow motion analysis, are observed to have developed perfectly linear (and force limited) strike paths. Interestingly as well, 60's studies on monkeys, researchers "couldn't induce concussion from linear blows, only from rotational accelerations". Nobody said research was pretty back then.
Measuring, testing devices, and standards don't exist for this aspect of helmet design. Standards bodies who need to adhere as well to economic principals to not abuse industries with cost burden make it unlikely standards will change. Secondly, helmet manufactures who add words like "concussion reducing" or totally separate topic, multi impact use, basically are penalized for this through becoming magnets for class action litigators who make livings by reading new features in helmet ads, waiting for an injury to occur contradictory to what the design improvement is meant to address, then suing. Cannondale and others have found that out. Awful.
But we have self will to preserve, and the internet. If, and that's your choice, you want to increase your head's protection, you kind of can. All hemets sold meet existing standards, so you can't do worse.
Rotative stress essentially can shear brain matter/structure/cells over a certain threshold, measured in a scientific unit. Video study of pro sports concussive injury makes estimates of ranges - above a threshold you're essentially guaranteed severe concussion, down to ranges where you're safe. 11,000 radians/second2 is downright awful, under 4,000 radians/second2 is "fine", middle is still concussion causing. Helmets can't prevent this. They can reduce, some can reduce the brain's exposure to those forces by several thousand of that unit, or call it 20-25%. Rotative, or impact reduction both spread out force over time and space to reduce its peak. Helmets that take this into consideration thus far mimic the brain's design of a layer of fluid between the brain and skull that stunts rotative energy in a variety of ways.
POC brand helmets offer an attempt at this that measurably addresses this type of impact. Scott has a 2013 design that does as well. Equestrian helmets have incorporated this. The Scott one is no heavier than a standard helmet. A real dumbed down statement is they have ways to slip internally from shell to head layer to absorb some of that force.
We spend lots of money on cool parts - light, functional, etc. Maybe allocate some extra to your next helmet. We don't crash much, but you will at some point. To be honest, I've never really banged my head in my life through skiing, snowboarding, biking, skateboarding - and all with a degree of "gusto" I'd add. But innovation that's no extra weight penalty, that's burdened by immovable bureaucracy and hindered by predatory legal action, is exactly the kind of innovation that I'd like to support. That's what the internet can help advance faster.
Read up. Consider a helmet that helps. There's not a lot of other products where I prefer the "minimum standard acceptable" as set, so why I do that in helmets is more just my lack of knowledge. I'm going to do a lot more research on my next one. You can purchase a directional improvement that you'll have to believe in. Swedish studies don't match US ones in measurement, but they show directional results that favor the claim of muting rotational force peaks. Neither is wrong, neither is "right". They are done my different equipment and different tests, but by active cyclist helmet designers who care about their heads and yours, and are trying to help.