One idea I’ve been musing about is the connections between IQ, Conscientiousness, and testosterone. IQ and Conscientiousness do not correlate to a remarkable degree - even though one would expect IQ to at least somewhat enable a long-term perspective, self-discipline, metacognition, etc! There are indications in studies of gifted youth that they have lower testosterone levels. The studies I’ve read on testosterone indicate no improvements to raw ability. So, could there be a self-sabotaging aspect to human intelligence whereby greater intelligence depends on lack of testosterone, but this same lack also holds back Conscientiousness (despite one’s expectation that intelligence would produce greater self-discipline and planning), undermining the utility of greater intelligence? Could cases of high IQ types who suddenly stop slacking and accomplish great things sometimes be due to changes in testosterone? Studies on the correlations between IQ, testosterone, Conscientiousness, and various measures of accomplishment are confusing and don’t always support this theory, but it’s an idea to keep in mind.
Fortunately for me, the FDA decided Smart Powder’s advertising was too explicit and ordered its piracetam sales stopped; I was equivocal at the previous price point, but then I saw that between the bulk discount and the fire-sale coupon, 3kg was only $99.99 (shipping was amortized over that, the choline, caffeine, and tryptophan). So I ordered in September 2010. As well, I had decided to cap my own pills, eliminating the inconvenience and bad taste. 3kg goes a very long way so I am nowhere close to running out of my pills; there is nothing to report since, as the pills are simply part of my daily routine.
(On a side note, I think I understand now why modafinil doesn’t lead to a Beggars in Spain scenario; BiS includes massive IQ and motivation boosts as part of the Sleepless modification. Just adding 8 hours a day doesn’t do the world-changing trick, no more than some researchers living to 90 and others to 60 has lead to the former taking over. If everyone were suddenly granted the ability to never need sleep, many of them would have no idea what to do with the extra 8 or 9 hours and might well be destroyed by the gift; it takes a lot of motivation to make good use of the time, and if one cannot, then it is a curse akin to the stories of immortals who yearn for death - they yearn because life is not a blessing to them, though that is a fact more about them than life.)
Brain focus pills largely contain chemical components like L-theanine which is naturally found in green and black tea. It’s associated with enhancing alertness, cognition, relaxation, arousal, and reducing anxiety to a large extent. Theanine is an amino and glutamic acid that has been proven to be a safe psychoactive substance. There are studies that suggest that this compound influences, the expression in the genes present in the brain which is responsible for aggression, fear and memory. This, in turn, helps in balancing the behavioural responses to stress and also helps in improving specific conditions, like Post Traumatic Stress Disorder (PTSD).
Mercury exposure is among several other heavy metals, such as lead, aluminium and cadmium, that have been implicated in the aetiology of ADHD. Childhood exposure to mercury is predominantly through the consumption of seafood, dental amalgams and vaccines containing thimerosal. The reason why mercury can be so problematic, as well as other metals, is that it is capable of breaching the blood brain barrier. This is the brain’s ‘high fortress’, an intelligent gateway system that filters through molecules that are needed in the brain such as cells, nutrients and signalling molecules, and filters out pathogens and toxins.
Such competitive anxieties are already being felt in the workplace. Recently an advice column in Wired featured a question from a reader worried about "a rising star at the firm" who was "using unprescribed modafinil to work crazy hours. Our boss has started getting on my case for not being as productive." And on internet forums such as ImmInst (Immortality Institute), whose members share a nerdy passion for tweaking their cognitive function through drugs and supplements, people trade advice about dosages and "stacks" - improvised combinations - of neuroenhancers ("Cut a tablet into fourths and took 25mg every four hours, four times today, and had a great and productive day - with no side-effects"). In one recent post a 52-year-old - who was working full time, studying for an advanced degree at night and "married, etc" - wrote that after experimenting with modafinil he had settled on two daily doses of 100mg each. He believed that he was "performing a little better", adding: "I also feel slightly more animated when in discussion."
It’s that time of the year again. It’s Blue Monday. We’re halfway into January, trudging through the deepest and darkest of the winter months, as we try to keep our heads high after the Christmas festivities with the motivation of our New Year’s resolutions. Some of you may have never heard of Blue Monday and let’s just say you’re not exactly missing out.
The blood half-life is 12-36 hours; hence two or three days ought to be enough to build up and wash out. A week-long block is reasonable since that gives 5 days for effects to manifest, although month-long blocks would not be a bad choice either. (I prefer blocks which fit in round periods because it makes self-experiments easier to run if the blocks fit in normal time-cycles like day/week/month. The most useless self-experiment is the one abandoned halfway.)
Another prescription stimulant medication, modafinil (known by the brand name Provigil), is usually prescribed to patients suffering from narcolepsy and shift-work sleep disorder, but it might turn out to have broader applications. “We have conducted at the University of Cambridge double-blind, placebo-controlled studies in healthy people using modafinil and have found improvements in cognition, including in working memory,” Sahakian says. However, she doesn’t think everyone should start using the drug off-label. “There are no long-term safety and efficacy studies of modafinil in healthy people, and so it is unclear what the risks might be.”
As expected since most of the data overlaps with the previous LLLT analysis, the LLLT variable correlates strongly; the individual magnesium variables may look a little more questionable but were justified in the magnesium citrate analysis. The Noopept result looks a little surprising - almost zero effect? Let’s split by dose (which was the point of the whole rigmarole of changing dose levels):
Took full pill at 10:21 PM when I started feeling a bit tired. Around 11:30, I noticed my head feeling fuzzy but my reading seemed to still be up to snuff. I would eventually finish the science book around 9 AM the next day, taking some very long breaks to walk the dog, write some poems, write a program, do Mnemosyne review (memory performance: subjectively below average, but not as bad as I would have expected from staying up all night), and some other things. Around 4 AM, I reflected that I felt much as I had during my nightwatch job at the same hour of the day - except I had switched sleep schedules for the job. The tiredness continued to build and my willpower weakened so the morning wasn’t as productive as it could have been - but my actual performance when I could be bothered was still pretty normal. That struck me as kind of interesting that I can feel very tired and not act tired, in line with the anecdotes.
Oxidative stress refers to a biochemical process that occurs as a result of an accumulative everyday exposure to toxic burdens such as chemicals in cosmetics, furniture, paints, cars, and pollution. Our body has its own way of armouring itself from the damage that exposure to toxins can create through its production of endogenous antioxidants, which is nature’s way of neutralising oxidative stress. Although we have our own production of these wonder molecules, when we are continuously overloaded with toxins in our environment and have problems detoxifying, the liver can become overwhelmed. Research shows that over time oxidative stress can lead to an increase in inflammatory molecules such as cytokines, which have been shown to correlate with depression (5).This is why it is important to have a high intake of nutrients that support the liver in metabolising and removing toxins from the body, as well as regulating the inflammatory response. There are a few things we can change in our diet to support this area, for example eating foods such as the cruciferous family of vegetables which includes kale, cauliflower, broccoli and cabbage. These are particularly effective at supporting the liver in ushering out toxins as they all share an antioxidant compound called indole-3 Carbinol, which plays an important role in liver health (6). In addition, bitter greens such as collard greens, rocket, chicory and swiss chard are also great for supporting the liver’s own antioxidant defence system.
Coconut oil was recommended by Pontus Granström on the Dual N-Back mailing list for boosting energy & mental clarity. It is fairly cheap (~$13 for 30 ounces) and tastes surprisingly good; it has a very bad reputation in some parts, but seems to be in the middle of a rehabilitation. Seth Robert’s Buttermind experiment found no mental benefits to coconut oil (and benefits to eating butter), but I wonder.
Like everything else in your body, the brain cannot work without energy. The ability to concentrate and focus comes from an adequate, steady supply of energy - in the form of glucose in our blood to the brain. Achieve this by choosing wholegrains with a low-GI, which release glucose slowly into the bloodstream, keeping you mentally alert throughout the day. Opt for 'brown' wholegrain cereals, granary bread, rice and pasta.
Qualia claims that its product stems from a new approach to science based on “principled meta-analysis and synthesis of existing research” to optimize “memory, focus, the speed of information processing, and pattern analysis.” The bottom line, however, is in its online medical disclaimer, which says: “These statements have not been evaluated by the Food and Drug Administration. . . . No claims are made about the safety of this product, nor are any medical or psychological benefits claimed.”
"They're not regulated by the FDA like other drugs, so safety testing isn't required," Kerl says. What's more, you can't always be sure that what's on the ingredient label is actually in the product. Keep in mind, too, that those that contain water-soluble vitamins like B and C, she adds, aren't going to help you if you're already getting enough of those vitamins through diet. "If your body is getting more than you need, you're just going to pee out the excess," she says. "You're paying a lot of money for these supplements; maybe just have orange juice."
The ‘Brain-Gut Axis’ is a term used to describe the two-way communication system between our digestive tract and the brain. A growing body of research into this axis demonstrates how much influence the gut can have over the brain and vice versa (1). When we speak about reactions to foods, we most commonly understand them as immediate and often dangerous allergic responses, such as the constriction of the throat and trouble breathing, or dizziness and fainting. It is usually easy to pinpoint the food that causes these reactions because of the immediate immune system response, caused by a type of immune cell known as IgE antibodies. In contrast to this, food intolerances are mediated by IgG antibodies and these reactions can take up to 48 hours to have an effect. Symptoms related to IgG reactions can often be manifested as chronic issues like joint ache, IBS and depression or anxiety, which are often overlooked and not associated with what we eat.
Though their product includes several vitamins including Bacopa, it seems to be missing the remaining four of the essential ingredients: DHA Omega 3, Huperzine A, Phosphatidylserine and N-Acetyl L-Tyrosine. It missed too many of our key criteria and so we could not endorse this product of theirs. Simply, if you don’t mind an insufficient amount of essential ingredients for improved brain and memory function and an inclusion of unwanted ingredients – then this could be a good fit for you.
This is the same fallacious argument made for superfoods. The same levels of dietary nutrients can be supplied by eating more of other foods. Caviar contains more omega-3s than salmon, but the typical serving of caviar is much smaller than the typical serving of salmon. And it’s possible to get plenty of omega-3s in a varied diet without eating either one.
A key ingredient of Noehr’s chemical “stack” is a stronger racetam called Phenylpiracetam. He adds a handful of other compounds considered to be mild cognitive enhancers. One supplement, L-theanine, a natural constituent in green tea, is claimed to neutralise the jittery side-effects of caffeine. Another supplement, choline, is said to be important for experiencing the full effects of racetams. Each nootropic is distinct and there can be a lot of variation in effect from person to person, says Lawler. Users semi-annonymously compare stacks and get advice from forums on sites such as Reddit. Noehr, who buys his powder in bulk and makes his own capsules, has been tweaking chemicals and quantities for about five years accumulating more than two dozens of jars of substances along the way. He says he meticulously researches anything he tries, buys only from trusted suppliers and even blind-tests the effects (he gets his fiancée to hand him either a real or inactive capsule).
The metal magnesium (Examine.com), like potassium (which didn’t help me), plays many biological roles and has an RDA for me of 400mg which is higher than I likely get (most people apparently get less, with 68% of American adults
Modafinil is a stimulant specifically designed to reduce fatigue and sleepiness. It was approved for treatment of narcolepsy in 1998, and although the exact mechanism behind its effects is not fully understood, most research indicates that modafinil also works by inhibiting reuptake of dopamine, which produces effects similar to those of methylphenidate. It’s also believed that by inhibiting dopamine uptake, more acetylcholine (another neurotransmitter) is released by the hippocampus, which leads to improved cognitive performance, specifically memory.
All clear? Try one (not dozens) of nootropics for a few weeks and keep track of how you feel, Kerl suggests. It’s also important to begin with as low a dose as possible; when Cyr didn’t ease into his nootropic regimen, his digestion took the blow, he admits. If you don’t notice improvements, consider nixing the product altogether and focusing on what is known to boost cognitive function – eating a healthy diet, getting enough sleep regularly and exercising. "Some of those lifestyle modifications," Kerl says, "may improve memory over a supplement."
My first dose on 1 March 2017, at the recommended 0.5ml/1.5mg was miserable, as I felt like I had the flu and had to nap for several hours before I felt well again, requiring 6h to return to normal; after waiting a month, I tried again, but after a week of daily dosing in May, I noticed no benefits; I tried increasing to 3x1.5mg but this immediately caused another afternoon crash/nap on 18 May. So I scrapped my cytisine. Oh well.
20 March, 2x 13mg; first time, took around 11:30AM, half-life 3 hours, so halved by 2:30PM. Initial reaction: within 20 minutes, started to feel light-headed, experienced a bit of physical clumsiness while baking bread (dropped things or poured too much thrice); that began to pass in an hour, leaving what felt like a cheerier mood and less anxiety. Seems like it mostly wore off by 6PM. Redosed at 8PM TODO: maybe take a look at the HRV data? looks interestingly like HRV increased thanks to the tianeptine 21 March, 2x17mg; seemed to buffer effects of FBI visit 22 March, 2x 23 March, 2x 24 March, 2x 25 March, 2x 26 March, 2x 27 March, 2x 28 March, 2x 7 April, 2x 8 April, 2x 9 April, 2x 10 April, 2x 11 April, 2x 12 April, 2x 23 April, 2x 24 April, 2x 25 April, 2x 26 April, 2x 27 April, 2x 28 April, 2x 29 April, 2x 7 May, 2x 8 May, 2x 9 May, 2x 10 May, 2x 3 June, 2x 4 June, 2x 5 June, 2x 30 June, 2x 30 July, 1x 31 July, 1x 1 August, 2x 2 August, 2x 3 August, 2x 5 August, 2x 6 August, 2x 8 August, 2x 10 August, 2x 12 August: 2x 14 August: 2x 15 August: 2x 16 August: 1x 18 August: 2x 19 August: 2x 21 August: 2x 23 August: 1x 24 August: 1x 25 August: 1x 26 August: 2x 27 August: 1x 29 August: 2x 30 August: 1x 02 September: 1x 04 September: 1x 07 September: 2x 20 September: 1x 21 September: 2x 24 September: 2x 25 September: 2x 26 September: 2x 28 September: 2x 29 September: 2x 5 October: 2x 6 October: 1x 19 October: 1x 20 October: 1x 27 October: 1x 4 November: 1x 5 November: 1x 8 November: 1x 9 November: 2x 10 November: 1x 11 November: 1x 12 November: 1x 25 November: 1x 26 November: 1x 27 November: 1x 4 December: 2x 27 December: 1x 28 December: 1x 2017 7 January: 1x 8 January: 2x 10 January: 1x 16 January: 1x 17 January: 1x 20 January: 1x 24 January: 1x 25 January: 2x 27 January: 2x 28 January: 2x 1 February: 2x 3 February: 2x 8 February: 1x 16 February: 2x 17 February: 2x 18 February: 1x 22 February: 1x 27 February: 2x 14 March: 1x 15 March: 1x 16 March: 2x 17 March: 2x 18 March: 2x 19 March: 2x 20 March: 2x 21 March: 2x 22 March: 2x 23 March: 1x 24 March: 2x 25 March: 2x 26 March: 2x 27 March: 2x 28 March: 2x 29 March: 2x 30 March: 2x 31 March: 2x 01 April: 2x 02 April: 1x 03 April: 2x 04 April: 2x 05 April: 2x 06 April: 2x 07 April: 2x 08 April: 2x 09 April: 2x 10 April: 2x 11 April: 2x 20 April: 1x 21 April: 1x 22 April: 1x 23 April: 1x 24 April: 1x 25 April: 1x 26 April: 2x 27 April: 2x 28 April: 1x 30 April: 1x 01 May: 2x 02 May: 2x 03 May: 2x 04 May: 2x 05 May: 2x 06 May: 2x 07 May: 2x 08 May: 2x 09 May: 2x 10 May: 2x 11 May: 2x 12 May: 2x 13 May: 2x 14 May: 2x 15 May: 2x 16 May: 2x 17 May: 2x 18 May: 2x 19 May: 2x 20 May: 2x 21 May: 2x 22 May: 2x 23 May: 2x 24 May: 2x 25 May: 2x 26 May: 2x 27 May: 2x 28 May: 2x 29 May: 2x 30 May: 2x 1 June: 2x 2 June: 2x 3 June: 2x 4 June: 2x 5 June: 1x 6 June: 2x 7 June: 2x 8 June: 2x 9 June: 2x 10 June: 2x 11 June: 2x 12 June: 2x 13 June: 2x 14 June: 2x 15 June: 2x 16 June: 2x 17 June: 2x 18 June: 2x 19 June: 2x 20 June: 2x 22 June: 2x 21 June: 2x 02 July: 2x 03 July: 2x 04 July: 2x 05 July: 2x 06 July: 2x 07 July: 2x 08 July: 2x 09 July: 2x 10 July: 2x 11 July: 2x 12 July: 2x 13 July: 2x 14 July: 2x 15 July: 2x 16 July: 2x 17 July: 2x 18 July: 2x 19 July: 2x 20 July: 2x 21 July: 2x 22 July: 2x 23 July: 2x 24 July: 2x 25 July: 2x 26 July: 2x 27 July: 2x 28 July: 2x 29 July: 2x 30 July: 2x 31 July: 2x 01 August: 2x 02 August: 2x 03 August: 2x 04 August: 2x 05 August: 2x 06 August: 2x 07 August: 2x 08 August: 2x 09 August: 2x 10 August: 2x 11 August: 2x 12 August: 2x 13 August: 2x 14 August: 2x 15 August: 2x 16 August: 2x 17 August: 2x 18 August: 2x 19 August: 2x 20 August: 2x 21 August: 2x 22 August: 2x 23 August: 2x 24 August: 2x 25 August: 2x 26 August: 1x 27 August: 2x 28 August: 2x 29 August: 2x 30 August: 2x 31 August: 2x 01 September: 2x 02 September: 2x 03 September: 2x 04 September: 2x 05 September: 2x 06 September: 2x 07 September: 2x 08 September: 2x 09 September: 2x 10 September: 2x 11 September: 2x 12 September: 2x 13 September: 2x 14 September: 2x 15 September: 2x 16 September: 2x 17 September: 2x 18 September: 2x 19 September: 2x 20 September: 2x 21 September: 2x 22 September: 2x 23 September: 2x 24 September: 2x 25 September: 2x 26 September: 2x 27 September: 2x 28 September: 2x 29 September: 2x 30 September: 2x October 01 October: 2x 02 October: 2x 03 October: 2x 04 October: 2x 05 October: 2x 06 October: 2x 07 October: 2x 08 October: 2x 09 October: 2x 10 October: 2x 11 October: 2x 12 October: 2x 13 October: 2x 14 October: 2x 15 October: 2x 16 October: 2x 17 October: 2x 18 October: 2x 20 October: 2x 21 October: 2x 22 October: 2x 23 October: 2x 24 October: 2x 25 October: 2x 26 October: 2x 27 October: 2x 28 October: 2x 29 October: 2x 30 October: 2x 31 October: 2x 01 November: 2x 02 November: 2x 03 November: 2x 04 November: 2x 05 November: 2x 06 November: 2x 07 November: 2x 08 November: 2x 09 November: 2x 10 November: 2x 11 November: 2x 12 November: 2x 13 November: 2x 14 November: 2x 15 November: 2x 16 November: 2x 17 November: 2x 18 November: 2x 19 November: 2x 20 November: 2x 21 November: 2x 22 November: 2x 23 November: 2x 24 November: 2x 25 November: 2x 26 November: 2x 27 November: 2x 28 November: 2x 29 November: 2x 30 November: 2x 01 December: 2x 02 December: 2x 03 December: 2x 04 December: 2x 05 December: 2x 06 December: 2x 07 December: 2x 08 December: 2x 09 December: 2x 10 December: 2x 11 December: 2x 12 December: 2x 13 December: 2x 14 December: 2x 15 December: 2x 16 December: 2x 17 December: 2x 18 December: 2x 19 December: 2x 20 December: 2x 21 December: 2x 22 December: 2x 23 December: 2x 24 December: 2x 25 December: 2x ran out, last day: 25 December 2017 –>
Pop this pill and improve your memory. Swallow that one and reduce your cognitive decline. We see ads for such products all the time and I suspect they will increase as the baby boomers reach senior citizenhood. The most popular brain boosting supplements are fish oil pills and they are also probably the best studied ones. The results are not encouraging. When all the studies are pooled, we are left with the possibility of a barely significant improvement in recalling lists of words soon after they have been learned, but the effect does not last. Extracts of the ginkgo biloba tree are also popular, and here the prospects are even dimmer. There is no impact on memory, despite claims of increased circulation in the brain. And ginkgo can interfere with the action of anticoagulants and has also been shown to be an animal carcinogen.
That left me with 329 days of data. The results are that (correcting for the magnesium citrate self-experiment I was running during the time period which did not turn out too great) days on which I happened to use my LED device for LLLT were much better than regular days. Below is a graph showing the entire MP dataseries with LOESS-smoothed lines showing LLLT vs non-LLLT days:
The nootropics community is surprisingly large and involved. When I wade into forums and the nootropics subreddit, I find members trading stack recipes and notifying each other of newly synthesized compounds. Some of these “psychonauts” seem like they’ve studied neuroscience; others appear to be novices dipping their toes into the world of cognitive enhancement. But all of them have the same goal: amplifying the brain’s existing capabilities without screwing anything up too badly. It’s the same impulse that grips bodybuilders—the feeling that with small chemical tweaks and some training, we can squeeze more utility out of the body parts we have. As Taylor Hatmaker of the Daily Dot recently wrote, “Together, these faceless armchair scientists seek a common truth—a clean, unharmful way to make their brains better—enforcing their own self-imposed safety parameters and painstakingly precise methods, all while publishing their knowledge for free, in plain text, to relatively crude, shared databases."
It’s not clear that there is much of an effect at all. This makes it hard to design a self-experiment - how big an effect on, say, dual n-back should I be expecting? Do I need an arduous long trial or an easy short one? This would principally determine the value of information too; chocolate seems like a net benefit even if it does not affect the mind, but it’s also fairly costly, especially if one likes (as I do) dark chocolate. Given the mixed research, I don’t think cocoa powder is worth investigating further as a nootropic.
We recently held an informative event in London with Dr Gill Hart, a biochemist and expert in the field of food intolerances and their global effect on health and we wanted to share some of the highlights of what Dr Hart covered. Based on some of her recent research (1), the talk offered some interesting insights into how food intolerances may have a role to play in our mental health. It honed in on the differences between food allergies and food intolerances within our immune system; some of the ways that our immune system, gut and brain are believed to influence each other, and how food intolerances, therefore, can play a role in mental health symptoms. She also spoke about how to go about testing and managing these intolerances through elimination diet strategies.
And if you obtain your vitamin C from a multivitamin, you receive other key nutrients that many studies over the years have linked to healthy brain function, including beta carotene, iron, zinc, B12 and folic acid. In the June 1999 issue of the Journal of Biology and Psychiatry, for instance, researchers at Sweden's Gotenborg University reported that older people were more likely to score poorly on word memory tests if they had low levels of folic acid.
For example, a study published in the journal Psychopharmacology in 2000 found that ginkgo improved attention. A 2001 study in the journal Human Psychopharmacology suggested that it improves memory. Nevertheless, in a review of studies on ginkgo in healthy people, researchers found no good evidence that it improved mental abilities, according to a 2002 report in Psychopharmacology Bulletin.
I’ve been taking nootropics on and off for a month, and despite my spurts of productivity, I’m still not 100 percent sure that they’re working. I could well be placebo-ing myself into thinking I'm working harder and focusing better than I typically do. But apparently enough people are feeling some effect, placebo or not, because nootropics start-ups are thriving. There’s truBrain, Nootrobrain, Nootroo, and a host of others. Nootrobox, the company that makes my pills, says that it’s selling "five figures" worth of cognitive supplements monthly to customers that include top Silicon Valley executives and Hollywood moguls.
As Sulbutiamine crosses the blood-brain barrier very easily, it has a positive effect on the cholinergic and the glutamatergic receptors that are responsible for vital activities impacting memory, concentration, and mood. The compound is also fat soluble, which means it circulates rapidly and widely throughout the body and the brain, ensuring positive results. Thus, patients with schizophrenia and Parkinson’s disease will find the drug to be very effective.
Dr. Mosconi’s book is keystone book for advancing the dialogue and practice of integrative brain health. This is the book I’ve been waiting for. As someone who is obsessed with nutrition, it’s very hard to find REAL research and sound logic. There’s a lot of people who proclaim to be health experts, but few people who can say they are trained in both scientific and holistic approaches. Dr. Mosconi’s book FINALLY gets to the bottom of what we all need to know to take care of our brains.
Jump up ^ Weyandt LL, Oster DR, Marraccini ME, Gudmundsdottir BG, Munro BA, Zavras BM, Kuhar B (September 2014). "Pharmacological interventions for adolescents and adults with ADHD: stimulant and nonstimulant medications and misuse of prescription stimulants". Psychol. Res. Behav. Manag. 7: 223–249. doi:10.2147/PRBM.S47013. PMC 4164338. PMID 25228824.