The rate of cognitive decline with aging is quite variable. 

Identifying important components of this process is needed for developing interventions to reduce the burden of Alzheimer's and other dementias.

Excess inflammation has been linked to obesity as well as aging-related cognitive decline.

Archana Singh-Manoux and colleagues recently published a study of the association between blood markers of inflammation and cognitive decline.

This study used data from the U.K. Whitehall II cohort, a group of men and women between the ages of 35-55 at intake.

This cohort has now been studied over a 20 year follow up with interval assessments about every five years.

Two blood markers of inflammation were studied in this cohort: interleukin-6 (IL-6) and C-reactive protein (CRP).

The study found strong associations between both blood markers of inflammation and rates of obesity (BMI >30) in the chart shown here.

Cognitive decline was measured by decrease scores on the Minimental Status Exam and other neuropsychological tests during the follow up period.

The primary finding from the study was that elevated IL-6 levels but not CRP levels at baseline were associated with accelerated cognitive decline.

Subjects in the highest IL-6 blood level group showed an 85% increased rate in losing 3 or more points on the Minimental Status Exam.

The authors note there study does not prove causality between IL-6 levels and cognitive decline but that:

"Inflammation is likely to play a role because of its impact on cerebral small-vessel disease, which could lead to changes that affect cognitive ageing."

It is also possible, that some of the link between obesity and cognitive decline may be attributable to increased obesity-related inflammation.

The practical clinical potential would be to attempt to identify and reduce inflammation in those most at risk. Anti-inflammatory drugs such as naproxen (Aleve in U.S.) have not been generally effect in trials to reduce rates of Alzheimer's disease.

However, these trials have typically not targeted groups with the highest blood markers of inflammation.

Readers with more interest in this topic can access the free full-text manuscript by clicking on the link in the citation below.

Photo of great blue heron from South Padre Island, TX is from the author's files.

Chart is an original figure from data abstracted from the manuscript.

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Singh-Manoux A, Dugravot A, Brunner E, Kumari M, Shipley M, Elbaz A, & Kivimaki M (2014). Interleukin-6 and C-reactive protein as predictors of cognitive decline in late midlife. Neurology, 83 (6), 486-93 PMID: 24991031

Joe: My doctor told me to give up drinking, smoking, and fatty foods.

Sam: What will you do?

Joe: I think I’ll give up my doctor.

I try not to get too excited about memory benefits of supplements, because too often the claims are not substantiated by studies that are well controlled and peer reviewed. I now think resveratrol may be one of the few supplements that benefits brain function.

When I wrote my first blog on research on resveratrol benefits for brain function and memory, there were over 2,000 scientific papers.[1]Don't worry; I am only going to tell you about a few studies.

Resveratrol is an active ingredient in red wine. This compound has been credited for explaining why red-wine drinkers in France, who drink more wine than most people, are healthier than would be predicted by their lifestyle of little exercise and eating lots of cheese. The problem is most studies suggest you would have to drink a 100 or more glasses of red wine a day to get much resveratrol effect (and that effect would obviously be negated by a toxic dose of alcohol). An obviously more healthful choice is the highly concentrated pill forms of resveratrol that are now on the market.

Most of the protective biological actions associated with resveratrol have been associated with its scavenger properties for free radicals and the protective effects that it confers on the heart and diabetes. 

One important study comes from a diabetes research group in Brazil recently who reported a beneficial effect of resveratrol on diabetic rats.[2]Resveratrol (in a modest rat dose of 10 and 20 mg per kilogram per day for 30 days) prevented the impairment of memory induced by diabetes. Resveratrol may be protecting neuron terminals that diabetes can damage. An earlier study by another group showed resveratrol improved glucose metabolism and promoted longevity in diabetic mice.

Another benefit of resveratrol is the anti-oxidant property. The brain produces more free-radical damage than other organs, because it burns so much oxygen. Compared with other organs, the brain has especially low levels of antioxidant defense enzymes. 

One recent study has revealed resveratrol had protective effects against brain damage caused by a chemical that kills acetylcholine neurons. Injection of this toxin into the brain of rats impaired their memory performance in two kinds of maze tasks. The impairment was significantly reduced by repeated injection of resveratrol (10 and 20 mg/kg) per day for 25 days, beginning four days before the toxin injection.[3]

Another recent study examined effects on working memory in mice fed a resveratrol-supplemented diet for four weeks before being injected with a cytokine to induce inflammation and accelerate aging. Resveratrol significantly reduced memory impairment in the aged group, but not in the young adults[4]. The lack of benefit in young adults was a little misleading, in that there was a "ceiling effect" in that the young adults were not impaired by the cytokine injection.

 The practical issue for us is whether resveratrol will help cognitive function in humans, especially healthy humans. It seems likely because other substances that have strong anti-oxidant properties seem to improve memory capability. Because animal studies have shown promise for resveratrol in preventing or treatment several different conditions associated with aging, several human clinical trials have been initiated.[5]

 An impressive new study of older humans, male and female, has just been reported.[6]Twenty-three healthy, but overweight people completed 6 months of daily resveratrol intake (200 mg ― the commercial brand I take has 300 mg/capsule). A paired control group got placebo pills. A double-blind design assured that neither the subjects nor the experimenters knew which individuals were in each group during data processing. Memory tests of word recall revealed significant improvement in the resveratrol group. Resveratrol also increased brain-scan measures of functional connectivity, which identified linked neural activity between the hippocampus and several areas of cerebral cortex.

Because others had shown that resveratrol increased insulin sensitivity in humans, these authors examine several markers important to diabetes. Resveratrol decreased the standing levels of sugar-bound hemoglobin, a standard marker for glucose control.  

What foods besides red grapes have resveratrol? The most likely other sources you would eat or drink are blueberries, cranberries, and peanuts. It is not likely that you could drink or eat enough of such substances to get enough resveratrol to do much good. Because of the scientifically documented benefits of resveratrol, highly concentrated supplements are now on the market (I have been taking it for a couple of years). I haven't given up my two glasses of red wine each day, but I have started taking one of the supplements. I haven't seen any reports that high doses of resveratrol are toxic.

---

[1] http://thankyoubrain.blogspot.com/2010/04/resveratrol-red-wine-magic-chemical.htmlApril 4, 2010.

[2] Schmatz R, et al. (2009). Resveratrol prevents memory deficits and the increase in acetylcholinesterase activity in streptozotocin-induced diabetic rats. Eur J Pharmacol. 2009 May 21;610(1-3):42-8. Epub 2009 Mar 19.

[3] Kumar, A. et al. 2007. Neuroprotective effects of resveratrol against intracerebroventricular colchicine-induced cognitive impairment and oxidative stress in rats. Pharmacology.79 (1): 17-26. DOI: 10.1159/000097511

[4] Abraham, J., and Johnson, R. W. 2009. Consuming a diet supplemented with resveratrol reduced infection-related neuroinflammation and deficits in working memory in aged mice. Rejuvenation research. 12 (6): 445-453.  DOI: 10.1089/rej.2009.0888

[5]Smoliga, J. M. et al. (2011). Resveratrol and health – a comprehensive review of human clinical trials.  Mol. Nutrition Food Res. 55: 1129-1141

[6] Witte, A. V., et al. (2014) Effects of resveratrol on memory performance, hippocampal functional connectivity, and glucose metabolism in healthy older adults. J. Neuroscience. 34 23): 7862-7870.

"Memory Medic's latest book is for seniors (Improve Your Memory for a Healthy Brain. Memory Is the Canary in Your Brain's Coal Mine," available in inexpensive e-book format at https://www.smashwords.com/books/view/496252.  See also his recent book, "Mental Biology. The New Science of How the Brain and Mind Relate" (Prometheus).

There is a growing research body of evidence to support beneficial effects of a Mediterranean diet on brain health.

In previous posts I have reviewed research on the Mediterranean diet and:

Cognitive Decline

Alzheimer's Disease Prevention

A recent study adds an important element in potential mechanisms for the beneficial effects of the Mediterranean diet.

Marta Crous-Bou and colleauges from Harvard University and the University of Washington published a study of the Mediterranean diet and chromosome telomere length.

This analysis used the large Nurses' Health Study cohort, blood samples and dietary questionnaires. Blood samples were analyzed for chromosome telomere length.

Chromosome telomere length has emerged as a biomarker of aging. DNA chromosome telomere lengths decline with age and shortened telomere lengths are associated with shortened life expectancy. 

The natural process of telomere shortening appears accelerated by inflammation and may be modified by lifestyle behaviors including dietary composition.

In the current study, subjects regularly completed dietary questionnaires. These questionnaires were rated on compliance with the Mediterranean diet on nine variables:

1. Vegetables
2. Fruits
3. Nuts
4. Whole grains
5. Legumes
6. Fish
7. Monounsaturated fat to saturated fat ratio
8. Red meat consumption
9. Alcohol intake

Median values for variables 1-8 were identified and subjects received a score of 1 if they were above the median (below median for red meat consumption). One point was awarded for consuming between 5 and 15 grams of alcohol per day.

Telomere length shortening was associated with older age and heavier cigarette consumption history.

Subjects were grouped into quintiles (20%) groups from lowest to highest Mediterranean diet score.

After adjusting for confounding variables, telomere length was statistically linked to Mediterranean diet score. Those with higher ratings on Mediterranean diet had longer telomeres indicating better aging.

The highest quintile group reported the following mean daily servings for each category: Vegetables (4.3 servings per day), fruits (3.2), whole grains (2.1), fish (0.5), red meat (0.5), legumes (0.6) and nuts (0.5).

The authors note they were unable to identify any single variable that had a strong independent effect. The effect appeared to be a combined global effect of the Mediterranean diet score.

This is an important study because it adds evidence for a biological mechanism for some of the previously reported clinical advantages associated with a Mediterranean diet. 

However, this study is limited by being primarily cross-sectional in design. It does not inform on whether changing diet to a Mediterranean type reduces rate of telomere shortening. 

Readers with more interest in this research can access the free full-text manuscript by clicking on the citation link below.

Photo of foods highlighted in the Mediterranean diet is an original photo from my files.

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Crous-Bou M, Fung TT, Prescott J, Julin B, Du M, Sun Q, Rexrode KM, Hu FB, & De Vivo I (2014). Mediterranean diet and telomere length in Nurses' Health Study: population based cohort study. BMJ (Clinical research ed.), 349 PMID: 25467028

Randomized clinical trials provide one of the best ways to test new obesity interventions.

These types of trials can examine effects of specific diets, new pharmacological treatment and new surgical treatments.

Here are some of the recent published trials that caught my attention in the last years.

Clicking on the title will take you to the PubMed abstract for more information. Additionally, some of the abstracts will have links to full-text manuscripts.

Lorcaserin: Safety and efficacy

This manuscript examined the results and safety of two previously published randomized trials of locarserin leading to FDA approval for obesity. Lorcaserin is a serotonin receptor 2 agonist. This manuscript noted more weight loss with this drug at one year (5.8% of body weight vs 2.5% of body weight for placebo). The drug appeared safe with no evidence of heart valve problems previously seen in some weight loss drugs.

Exercise effects in obese adolescents

In this randomized trial, obese adolescents participated in one of four groups: aerobic training, resistance training, combined aerobic and resistance and control. Body fat was measured using MRI at baseline and 6 months. The study found significant reductions in body fat in all three exercise groups compared to controls. Adolescents who had high adherence to the combined training regimen fared best.

Bariatric surgery compared to medical obesity management in type 2 diabetes

Weight loss surgery is frequently reserved for the most obese that have a significant obesity-related medical condition. Less severely obese individuals (BMI 30 to 35) with type 2 diabetes have received less attention. In this study individuals with type 2 diabetes and a BMI of between 30 and 35 were randomized to bariatric surgery or aggressive medical therapy. The bariatric surgery group at six months had higher diabetes remission rates (65% vs 0%) and greater weight loss. 

Vagal nerve blockade as a treatment of obesity

The vagus nerve running from the GI tract to the brain in known to be involved in control of food intake and satiety. This study examined a clinical trial of a surgical intervention that allows for intra-abdominal vagal blockade. This trial found some evidence for superiority of vagal blockade vs sham intervention, but the effects were relatively mild and did not meet pre-study targets for significant advantage.

Inpatient treatment for severe obesity in children and adolescents

Treating severe obesity in children and adolescents is a serious clinical challenge. A group in the Netherlands examined the potential for a partial hospitalization over 6 months to boost weight loss in obese children and adolescents. The hospitalized group had greater weight loss at 6 months compared to an outpatient control group. However, these favorable outcomes were not present at 12 month and 24 months follow up.

Photo of female cardinal in the snow is from my files.

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Brain inflammation produces a variety of emotional, behavior and cognitive symptoms.

I remember clearly a patient I cared for with central nervous system lupus erythrematosis (SLE). With SLE flairs she developed flagrant psychotic symptoms including hallucinations requiring inpatient psychiatric care.

Between flares she had no significant psychiatric symptoms.

Nicole Castanon and two colleagues from France have published a review of the role of obesity-associated inflammation and brain dysfunction.

Obesity is linked to a variety of blood markers of inflammation including proinflammatory cytokines, IL-6, interleuking and TNF. These inflammatory markers diminish with weight loss accomplished by either diet restriction or bariatric surgery.

The authors note evidence obesity is associated with the following:

• Depression (not all studies and not confirmed in animal models)
• Anxiety
• Memory and other cognitive impairment
• Increased age-related cognitive decline

So how could primarily a peripheral body condition impact the brain?

Figure from Castonon et al

The authors summarize potential mechanisms in a nice figure that I have reproduced here as it is open-access under the Creative Common Attribution License. See the citation below for the source of this figure.

Increased adipose (fat) tissue is known to promote local inflammation including recruitment of microphages and secretion of inflammatory chemicals. 

This peripheral adipose inflammation can transfer to the brain through the vagus nerve, hormones or other blood inflammtory chemicals and cellular pathways.

Brain evidence for this transfer has been noted via inflammation in the hippocampus, basal ganglia and prefrontal cortex.

Additional obesity-related brain inflammatory effect has been noted through dysruption of the hypothalamic/pituitary/adrenal (HPA) axis and changes in brain serotonin and dopamine metabolism.

A second potential pathway is described as working through changes in the gut in obesity. Obesity is linked to changes in gut bacteria composition, a change that results in increased gut permeability. This permeability change potentially promotes increased gut-blood absorption of endotoxins that can promote a systemic anti-inflammatory response. 

The authors note their review of this topic supports weight management approaches to limit the effect of obesity on the brain. Additionally, there may be some evidence to investigate anti-inflammatory diet and drug interventions for those with combined obesity and brain disorders. 

Readers with more interest in this topic can access the free full-text manuscript by clicking on the link below.

Photo of blue jay in the snow is from the author's files.

Figure of obesity-brain interaction is from Castanon, Lasselin and Capuron, citation below.

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Castanon N, Lasselin J, & Capuron L (2014). Neuropsychiatric comorbidity in obesity: role of inflammatory processes. Frontiers in endocrinology, 5 PMID: 24860551

Dietary intake of whole grains and fiber shows consistent beneficial effects on a variety of health and mortality measures.

In a post in 2011, I reviewed study results from the NIH-AARP cohort. That study reported reduced cardiovascular disease but not cancer in men and women with the highest fiber intake.

A recent Harvard University study examined mortality risk in a group of U.S. health professionals grouped by level of whole grain intake.

Participants in this study were over 118,000 men and women from the Health Professionals Follow-Up Study and the Nurses' Health Study.

Participants completed dietary questionnaires every two to four years over the course of the study. Each participant had an estimated daily grain consumption level calculated from dry weight whole grain intake of rice, bread, pasta and breakfast cereals.

Participants were grouped into quintiles (5 groups each containing 20% of the sample) from lowest to highest whole grain intake. Mean levels of whole grain daily intake in three of the five quintiles for women/women were reported:

• Lowest (g/day): 4.2/5.9
• Low: 9.7/14.4
• Middle: 14.7/22.1
• High: 21.1/31.3
• Highest: 33.0/47.8

The study team follow participants for death using next of kin, postal information and the National Death Index.

Death certificate and medical record information was used to assign deaths into cardiovascular deaths (including myocardial infarction and stroke), cancer or other categories.

During the follow-up period of 26 years, 15,106 deaths were identified with 2989 assigned to the cardiovascular disease death group, 5964 assigned to cancer and 6,153 assigned to other causes.

Analysis of the rates of heart/stroke death rates by whole grain intake showed a consistent finding in men and women.

Those in the highest whole grain intake group had about a 15% reduction in rates of heart/stroke deaths during the follow-up period (see chart left).

Additionally, total mortality was about 8% over the follow-up period in the highest whole grain intake group.

This estimate controlled for potential confounding variables such as age, BMI, smoking status, physical activity and aspirin use.

Getting to the high or higher quintile group status takes between two and three daily servings of whole wheat, whole oats, whole cornmeal, whole rye, brown rice, popcorn or bran additive.

One concern with whole grains is the carbohydrate levels. Individuals on a low carbohydrate diet may find a big portion of their daily carbohydrate limit is taken up with two or three portions of whole grain. Using bran additives, like All-Bran Buds may reduce the carbohydrate load associated with whole grains.

The authors note their findings are consistent with several other studies linking whole grain intake to lower heart/stroke death risk. Additionally they note their findings support federal guidelines urging daily whole grain intake.

This is an important study due to the large sample size, ability to examine effects in both men and women and the quality of dietary and mortality data.

Photo of blue jay is from the author's files.

Chart was an original chart made by author using data from the manuscript.

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Wu H, Flint AJ, Qi Q, van Dam RM, Sampson LA, Rimm EB, Holmes MD, Willett WC, Hu FB, & Sun Q (2015). Association Between Dietary Whole Grain Intake and Risk of Mortality: Two Large Prospective Studies in US Men and Women. JAMA internal medicine PMID: 25559238

Here are links to a series of abstracts that I am reviewing for this month.

I will do a full post on some of the most interesting and important research on this topic over the next month. 

Clicking on the title will link you to the PubMed abstract. Most articles highlighted in this post have free full-text access.

Mediterranean Diet and Chromosome Telomere Length

This recent study from the Harvard Nurse cohort examined telomere length in reference to a score of adherence to a Mediterranean type diet. Nurses with higher Mediterranean type diets had longer telomere lengths suggesting better chromosome aging.

Genotype, Cognition and the Mediterranean Diet

This prospective study of diet intervention examined the role of genes on response to diet for changes in cognition measured by the Mini-mental Status Examination and the Clock Drawing Test. The study found positive effects of a Mediterranean diet intervention on cognition although effects were not as robust in those with the Alzheimer's linked APOE gent.

Obesity, Inflammation and Brain Disorders

This review article summarizes some of the current knowledge on the link between obesity, inflammation and potential brain effects. The authors note these effects may be due to changes in neurocircuitry, brain hormones, neurotransmitters or neurogenesis.

Brain Inflammatory Markers and Cognitive Decline

This prospective study examine levels of two blood markers of inflammation, IL-6 and CRP from the Whitehall prospective cohort. Elevated IL-6 but CRP predicted greater cognitive decline over a 6 year period. 

Water for Soda Switch Lowers Metabolic Syndrome Risk

In a prospective study of switching water for soda, the research team found reduced rates of metabolic syndrome in obese subjects but not overweight subjects. 

Effects of CPAP With or Without Weight Loss in Sleep Apnea

The authors in this New England Journal of Medicine study found superiority of adding weight loss to CPAP in the outcome of a series of subjects with sleep apnea.

Low Carb versus Low Fat Diets in Type 2 Diabetes

This study compared outcome in Type 2 diabetes between those following a low carbohydrate versus a low fat diet. The team found both groups lost similar amounts of weight but the low carbohydrate groups had superior improvement in levels of markers for inflammation.

Bariatric versus Medical Treatment of Type 2 Diabetes

This study compared two types of bariatic surgery to medical weight loss intervention in one year outcome for type 2 diabetics. Surgical interventions showed superiority in weight loss and diabetes control.

Photo of outdoor dining in Dingle, Ireland is from the author's files.

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I recently reviewed a study of the epidemiology of drug use in Europe. 

This original post can be found here. 

This study examined patterns of levels for specific drugs of abuse in waste water.

One finding I found interesting was the geographic distribution for the stimulants including cocaine, amphetamine and methamphetamine.

Methamphetamine levels in waste water were highest in Czech Republic, a nation not found on any other top drug level lists. Slovakia came in fourth in methamphetamine levels.

I followed up on this finding using the Google tool called Google Trends. I also have previously posted on the potential for using Google Trends to track drug use and interest geographically here.

Google Trends calculates a relative index for search terms by country. Unfortunately, Google Trends does not allow for limiting searches to Europe. But with a worldwide search, you get the following map for a search for methamphetamine (prescription drug subcategory):

Czech Republic comes up fifth on the worldwide regional interest for methamphetamine search while Slovakia places seventh.  The U.S., Guam and New Zealand were 1, 2 and 3. Australia was fourth and Canada sixth.

The Czech Republic has been known to have had a problem with large numbers of methamphetamine labs that have been shut down and the use of pseudoephedrine imported from Poland for methamphetamine manufacture (Wikipedia).

Neither Czech Republic or Slovakia come up in regional interest for amphetamine or cocaine. This was also found in the waste water survey.

This Google Trend result supports the validity of the waste water study of Ort et al and the geographic regional variation in pattern, type and level of drug use and abuse. 

Changes in waste water concentrations of specific drugs like methamphetamine may be a valuable way to monitor effectiveness of public health intervention efforts

Molecular model is methamphetamine from a Wikipedia Commons File authored by sbrools.

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Ort C, van Nuijs AL, Berset JD, Bijlsma L, Castiglioni S, Covaci A, de Voogt P, Emke E, Fatta-Kassinos D, Griffiths P, Hernández F, González-Mariño I, Grabic R, Kasprzyk-Hordern B, Mastroianni N, Meierjohann A, Nefau T, Ostman M, Pico Y, Racamonde I, Reid M, Slobodnik J, Terzic S, Thomaidis N, & Thomas KV (2014). Spatial differences and temporal changes in illicit drug use in Europe quantified by wastewater analysis. Addiction (Abingdon, England), 109 (8), 1338-52 PMID: 24861844

Happy New Year to All! Hoping everyone has a healthy, happy and productive year in 2015.

I have been working on a topic list for 2015. I will be following my pattern of focusing on a specific brain research topic each month.

During the month I will post primarily on that topic after reviewing relevant research abstracts and manuscripts.

The topic list is taken from areas showing the most reader interest as well as covering area not recently reviewed.

I occasionally post off topic when a specific issue of importance arises.

The topic outline for 2015 will be:
January: Diet, Weight Loss and the Brain
February: Exercise
March: Parenting
April: Attention deficit disorder
May: Conduct disorder
June: Alzheimer's disease
July: Bipolar disorder
August: Social anxiety disorder
September: Migraine headaches
October: Neuropsychology
November: Brain imaging
December: Genetics

Brain Posts aims to select brain research relevant to translation to better clinical care for brain disorders.

Additionally, the blog provides an incentive for me to continue reading, learning and trying to keep up with key brain research advances.

Today's photo is from my files of an edited photo from the Rhema church Christmas lights.

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“Life, liberty, and the pursuit of happiness:” some people might argue that the U.S. Constitution endorses hedonism, and indeed many politicians want to ignore or get rid of the Constitution, but not necessarily because of hedonism. We should not be dismissive about encouraging people to pursue happiness. Happiness can be good for your brain. Depression is surely bad for your brain.

Positive mood states promote more effective thinking and problem solving. A recent scholarly report[1] reviews the literature demonstrating that positive mood broadens the scope of attentiveness, enhances semantic associations over a wider range, improves task shifting, and improves problem-solving capability. The review also documents the changes in brain activation patterns induced by positive mood in subjects while solving problems. Especially important is the dopamine signaling in the prefrontal cortex.

Published studies reveal that a variety of techniques are used to momentarily manipulate mood. These have included making subjects temporarily happy or sad by asking subjects to recall emotionally corresponding past experiences or to view film clips or hear words that trigger happy or sad feelings,

The effect of happiness on broadened attentiveness arises because the brain has better cognitive flexibility and executive control, which in turn makes it easier to be more flexible and creative. Happy problem solvers are better able to select and act upon useful solutions that otherwise never consciously surface. Happiness reduces perseverative tendencies for errant problem-solving strategies. The broadened attentiveness, for example, allows people to attend to more stimuli, both in external visual space and in internal semantic space, which in turn enables more holistic processing. For example, in one cited study, experimenters manipulated subjects’ momentary mood and then measured performance on a task involving matching of visual objects based on their global versus local shapes. Happy moods yielded better global matching.

Other experiments report broader word association performance when subjects are manipulated to be happier. For example, subjects in a neutral mood would typically associate the word “pen” as a writing tool and would associate it with words like pencil or paper. But positive mood subjects would think also of pen as an enclosure and associate it with words like barn or pigs. This effect has been demonstrated with practical effect in physicians, who, when in a happy mood, thought of more disease possibilities in making a differential diagnosis.
The review authors reported their own experiment on beneficial happy mood effects on insightfulness, using a task in which subjects were given three words and asked to think of a fourth word that could be combined into a compound word or phrase. For example, an insightful response to “tooth, potato, and heart” might be “sweet tooth, sweet potato, and sweetheart.” Generating such insight typically requires one to suppress dominant “knee jerk” responses such as associating tooth with pain and recognize that pain does not fit potato while at the same time becoming capable of switching to non-dominant alternatives.

Other cited experiments showed that happy mood improved performance on “Duncker’s candle task.”  Here, subjects are given a box of tacks, a candle, and a book of matches, and are asked to attach a candle to the wall in a way that will burn without dripping wax on the floor. Subjects in a happy mood were more able to realize that the box could be a platform for the candle when the box is tacked to the wall.  

Such effects of happy moods seem to arise from increased neural activity in the prefrontal cortex and cingulate cortex, areas that numerous prior studies have demonstrated as crucial parts of the brain’s executive control network. Similar effects have been observed in EEG studies. Other research suggests that the happiness effect is mediated by increased release of dopamine in the cortex that serves to up-regulate executive control.
The review authors described a meta-analysis of 49 positive-psychology manipulation studies showing that momentary happiness is readily manipulated by such strategies as deliberate optimistic thinking, increased attention to and memory of happy experiences, practicing mindfulness and acceptance, and increasing socialization. The effect occurs in most normal people and even in people with depression, anxiety, and schizophrenia. Biofeedback training, where subjects monitor their own fMRI scans or EEGs, might be an even more effective way for people to train themselves to be happier.

The main point is that people can be as happy as they choose to be.

For more on how positive mood influences memory ability, see my new book, Memory Power 101 (http://skyhorsepublishing.com ). Memory Medic's latest book explores the biology of mind. See "Mental Biology. The New Science of How the Brain and Mind Relate" (Prometheus).

[1] Subramaniam, K. and Vinogradov, S. (2013). Improving the neural mechanisms of cognition through the pursuit of happiness. Frontiers in Human Neuroscience. 7 August. Doi: 10.3389/fnhum.2013.00452