Can Nootropics Improve Fluid Intelligence

Nootropics and Fluid Intelligence: The Complete Guide

What Is Fluid Intelligence?

Fluid Intelligence represents one’s ability to problem solve and reason without having previously acquired knowledge.1 The term was first coined in the early 1940s by Raymond Cattell.3 Cattell is the first to identify that Fluid Intelligence, which he also referred to as “fluid general ability,” is most easily measurable in tests which require adaptation to new situations. He also notes that crystallized intelligence is of little-to-no value in ‘new situation adaptation’-style testing.11 In the world of science and research, Fluid Intelligence is represented by the symbol Gf.2 And ultimately, the theory of Gf only transpired as an effort to justify human cognitive ability.5

One recent book entitled Aging and Decision Making defines Fluid Intelligence as reasoning ability, and more specifically explains Gf as the ability to create, alter, and manipulate various novel information in real time.17 Real time is a great phrase as it helps explain Gf as a major influence on micro activities within day-to-day life. The evolution of any novel problem obviously requires the ability to solve the problem. Therefore, it is very easy to understand how important Gf can be in achieving success in any selective area of life, or in life as a whole.

Drawing a comparative line that relates one’s Gf ability to one’s success in performance-based activities is nearly common sense. In the simplest of terms: it would make perfect sense for people possessing higher Gf ability to achieve greater success in situations that require performance, competition, or problem solving. These situations include: school and test taking, research and studying, career and job activities, athletic activity, reflex-oriented tasks, and any other performance-based activity. A more fluid problem solver (someone with a high Gf) would be more likely to calculate or simulate their way out of a problem than someone with a low Gf.

The Gf-Gc model of intelligence is the most basic, primitive scale of intelligence, but still the most studied, iron-clad, and the seminal idea that spawned so many other models and scales. Today, there are many more in-depth scales of models of intelligence that all work off the origin of the two-toned Horn-Cattell model of Fluid Intelligence and Crystallized Intelligence.21 The model clearly represents fluid ability as processing ability, flexible thinking and abstract reasoning; while depicting crystallized thinking as a result of accumulating simulations of flexible thinking.

What Is the Difference Between Fluid Intelligence and Crystallized Intelligence?

Crystallized Intelligence has been defined as many things, but probably one of the best ways would be as “the extent to which a person has absorbed the content of culture.”9 It is important to note that ‘culture’ can mean many things, including but not limited to: the culture of a society, the culture of a learning establishment, the culture of a sport or performance environment, or even the culture of a household. Crystallized intelligence is represented by the symbol Gc. Raymond Cattell deserves credit for first identifying both Gf and Gc, although both were also further investigated and researched by Cattell’s protégé John L. Horn.2 Cattell’s initial research, although rather simple, effectively defines both phrases (Fluid Intelligence and Crystallized Intelligence), as well as how they differ.

Cattell explains that mental capacity can be broken down into two kinds of primary characteristics which he labels “Fluid” and “Crystallized” (hence the birth of the phrases).

  • Fluid Intelligence is explained as the ability to discriminate and understand relations between data or any fundamentals. Cattell does associate fluid ability with the entire cortex.3
  • Crystallized Intelligence is explained as long developed discriminatory habits associated with a particular area or field. Cattell attributes any Crystallized Intelligence that forms originally to fluid ability, but also indicates it can only form from fluid ability-requiring tasks which do not require “insightful perception for successful operation.”3

David Geary (of the University of Missouri) takes Cattell’s research much further. Geary relates Gf to the dorsolateral prefrontal cortex and anterior cingulate cortex. This also associates Gf with attention span, short term memory, and the ability to problem solve and cope in novel situations.10

Comparatively, Gc is associated with regions of the brain that store long term memory, namely the hippocampus.10 It is very commonly defined as the ability to retrieve and use information acquired throughout a lifetime.18 In some research and studies, Crystallized Intelligence is called crystallized knowledge, which should be considered a synonym.

To summarize, Crystallized Intelligence (Gc) has a lot more to do with long-term memory, whereas Fluid Intelligence (Gf) has a lot to do with attention span, short term memory and new problem solving. It is also worth noting that a higher Gc is obtained more quickly from possessing a higher Gf.2 In other words, those who have high Fluid Intelligence are able to learn more permanent knowledge with value of a broader perspective (wisdom) faster.

Can Fluid Intelligence Be Improved?

David Geary also explains that fluid ability has evolved throughout the course of human history to match the novelty and change presented along the way.10 In other words, as the various stages of humanity evolved, so did the fluid ability to predict social situations and problem solve. Basic human evolution is evidence that Fluid Intelligence can be improved within the species. Aside from actual evolutionary changes in the human species itself, there are other ways to improve Gf in each individual, living human being as well.

Recent research is revealing that people are born with different Gf ability, and that Gf can be predicted via biological data (biomarkers, brain metrics, etc.).19 Developments like this help neuroscientists, doctors, and pharmacists better understand Gf, its neurobiological foundations, and its impact on the many outcomes of a life. In fact, some Gf performance tests have been developed which have the ability to predict many aspects of life (most notably career achievement, educational success, and social happiness).19 The idea of improving Gf is not new and has been long-sought by many specialists and professionals, and with varying degrees of success. Learning potential in itself has been defined by many sources as [basically] ‘one’s ability to improve cognitive function.’20 Despite its obvious effect on crystallized knowledge as well, learning potential was essentially created as a way to explain the ability to improve decision making and fluid thinking.

The brain’s use of neurotransmitters highlights one of the most practical ways to “hack the brain” into a greater Gf. Neurotransmitters are chemical substances released in the brain in response to various stimuli. Neurotransmitters are manipulated not only by situation-based stimuli, but also by the metabolization of various substances.12,13,14 Nootropics are substances usually classified as supplements which improve cognitive function to some extent in healthy people.15

What Nootropics Improve Fluid Intelligence?

nootropics that improve fluid iq

Nootropics have a long history of being used by many cultures throughout the world for their cognitive-related enhancements. This is no surprise either, as very real advantages can be created from many nootropics. The actual term “Nootropics” was first coined in 1972 by Corneliu Giurgea, a Romanian chemist.16 Regardless of when they were named, Giurgea outlined some basic classification principles for substances to qualify as a nootropic including:

  • The substance must enhance learning and memory to some extent.
  • The substance must enhance the resistance of learned behavior and memory to disruptive conditions.
  • The substance must protect the brain from a variety of chemical and physical injuries.
  • The substance must improve the function/efficacy of the cortical and subcortical control mechanisms.
  • The substance must be free of psychotropic-like pharmacological effects, free of major side effects, and possess low toxicity.16

That said, all nootropics technically qualify as “Nootropics that Improve Fluid Intelligence,” as all nootropics enhance cognitive function, memory, or learning. And some nootropics have been shown to achieve pretty influential impacts on Fluid Intelligence. One recent study even revealed an expectation of prolonged life of those subjects on some nootropic treatments (studied treatment of dementia patients given various nootropics regimens and other anti-dementia treatment).7

There have been many studies on Fluid Intelligence throughout the years, but one in particular proved rather early that Gf absolutely impacts one’s ability to succeed in school subjects. Specifically, the study found that Gf continued to influence Gc in their participants throughout the course of the study. The study lasted between 1972 and 1988, following more than nine thousand children throughout compulsory school.4 The reasons people use nootropics today can vary from person to person, but the most common reasons are for benefits to cognitive enhancements, memory, and Gf.

List of Nootropics Used to Improve Fluid Intelligence (Gf):

Huperzine A

Huperzine A is a special nootropic that has been used for many cognitive advantages, but most notably for increasing acetylcholine.

How Huperzine A Affects Gf

Recent studies have indicated that coordinated acetylcholine release between the prefrontal cortex and hippocampus supports learned behavior acquisition during cognitive-related tasks, mental performance and memory formation.22,23 It is more clear now than ever that acetylcholine has a direct physiological impact on the brain’s ability to form memories, recall memories, and perform certain cognitive functions, especially those related to the hippocampus.23 This explains why Huperzine A has been so notoriously used for Dementia (Alzheimer’s and similar thinking or memory impairment diseases). In fact, many studies have shown that Huperzine A will only continue to work better the older a subject gets and in parallel has provided the most drastic effects for systems which are deficient in acetylcholine.6 Huperzine A is in such great demand because it offers natural, memory-improving properties.8

The Pirate Botanicals Piratall and Pirate Blast formulae uses Huperzine A.


Hawthorn is a fruit-bearing nootropic plant also known as Crataegus. Hawthorn is known for its high content of flavonoids, which are typically used to support the circulatory system.

Hawthorn is also a strong adaptogen. Adaptogens help stabilize physiological processes and to help increase resistance to stress.24 It is typically found in nootropics formulae due to its ability to promote the efficacy of other nootropics. Basically, a number of active constituents in Hawthorn are able to stimulate neuroendocrine and immune systems during metabolization, enhancing a number of brain functions.26 The following antioxidant influences are acquired from Hawthorn:

  • Scavenging of reactive oxygen species
  • Improved superoxide dismutase
  • Enhanced catalase activity
  • Inhibiting tyrosinase activity
  • Inhibiting lipoxygenase activity
  • Alpha tocopherol protective function
  • Improved intracellular communication
  • Cell Viability increased
  • and more25

Hawthorn has been used for a long time in many cardiovascular or nerve-related tonics. And Hawthorn continues to be a valuable nootropic-adaptogen today.

The Pirate Botanicals Piratall formula uses Hawthorn.

Siberian Ginseng

Siberian Ginseng also goes by its scientific name, Eleutherococcus senticosus. It is a different type of ginseng than the more widely-available Panax Ginseng. People have been using Siberian Ginseng to improve focus, energy, and athletic performance. In fact, it has been used in traditional Chinese medicine for more than 2,000 years.27

A recent study of the multifunctional silver and gold nanoparticles of Siberian Ginseng revealed a great deal of benefits, also describing the herb as “simple, efficient, and ecofriendly.”28 The study investigated the adaptogen benefits of two important Siberian Ginseng components:

  • Siberian Ginseng Silver Nanoparticles (Sg-AgNPs)
  • Siberian Ginseng Gold Nanoparticles (Sg-AuNPs)

Research suggests Siberian Ginseng could be useful for things like breast cancer or even for its inhibitory effects of S. aureus, B. anthracis, V. parahaemolyticus, and E.coli. The silver and gold nanoparticles are particularly effective antioxidants, and can even be used in combination with other ingredients in anti-aging formulae.28

Siberian Ginseng is another great adaptogen nootropic. The Chinese and many other cultures since have understood the natural de-stressing properties of this powerful adaptogen. In depth phytochemical content analysis and reputable pharma-nutrition studies show that there is great value in E. senticosus; and it is more than reasonable to have found it used in traditional medicine.27,28 Strong adaptogens like Siberian Ginseng can help the brain achieve its optimum balance and lead to better performance.

The Pirate Botanicals Piratall formula uses Siberian Ginseng.


Guarana, also known by its scientific name Paullinia cupana, is an awesome source of energy and has been used by many cultures for weight control.29 The guarana plant is most sought after (and inherits its stimulating, energizing properties) from the caffeine content found in the seeds. In fact, the seeds are known to contain about 4 times the amount of caffeine found in coffee beans.30

Many people turn to energy drinks for their boost to attention-span and focus, alertness, cognitive function, memory and physical output.30 And many energy drink companies have recently chosen to eliminate synthetic caffeine anhydrous in exchange for higher quantities of Guarana. Synthetic caffeine has received some bad reputation in recent years due to how hazardous it can be to health in high quantities. Many people die from accidentally ingesting too much synthetic caffeine at once.31,32 Not only is it dangerously easy to overdose on synthetic caffeine, but it is also synthesized using many harsh chemicals. Natural caffeine metabolizes in the body straight from the plant extract and produces energy without the crash.

Guarana is known as an extremely effective stimulant, and even provides some antioxidant properties, making it an awesome nootropic to combat fatigue.30

The Pirate Botanicals Piratall and Pirate Blast formulae uses Guarana.


Yohimbe is very commonly employed for its stimulating properties and to counteract exhaustion. Yohimbine is the primary active constituent of the Yohimbe tree bark, and it is also an indole alkaloid.33 It has been a part of West African traditional medicine for a long time as a versatile herbal tonic.36 Yohimbe has since spread around the world, becoming a popular ingredient in many supplements and nootropic stacks.

Yohimbine blocks the pre-synamptic α2 receptors which ultimately facilitates release of many neurotransmitters, including norepinephrine.34 Norepinephrine is a powerful neuromodulator that aides in “rapid modulation cortical circuits and cellular energy metabolism.” Studies have revealed norepinephrine has an enormous effect on cognition.35 Cognition benefits like those offered by norepinephrine are great for formulae that combat fatigue and exhaustion. Many formulae are designed to enhance athletic performance.37

Yohimbe is often thought of as an energizing, stimulating, peppy herb. These traits make it an effective inclusion in any energy-based nootropic formula.

The Pirate Botanicals Pirate Blast formula uses Yohimbe.


Maca, also known by its scientific name as Lepidium meyenii, originates in Peru. The plant has also been cultivated in the area for more than 2,000 years. Even more amazing is that the plant is found exclusively in the Andes mountains above 4000 meters in altitude.38

maca nootropics and fluid iq

Maca is well-sought, worldwide for many purposes, but its very well known for its potency as an adaptogen. There are many experiments and studies which show Maca as providing a lot of energy and a huge boost to memory function and learning.38,39,40 The flavonoids have been suggested to improve mood,41 which can create a more balanced way of thinking and better cognitive focus. Many experimental models have shown that Maca not only possesses vast potential as a potent adaptogen, but that it can have a significant impact on better memory function.42 While many of the memory-enhancement trials have been performed only in animal models, Maca itself has been used in a traditional sense for these purposes in Peru by a number of cultures for a long time. Even the Incas used the herb for its nutritional and medicinal values.43

Maca’s incredible cognitive benefits and awesome adaptogen properties make it a strongly valuable nootropic.

The Pirate Botanicals Pirate Blast formula uses Maca.


Rhodiola rosea contains phenols, alkaloids, flavonoids, and other chemical constituents. It has been used for hundreds of years as a potent adaptogen and to increase physical endurance.

Rhodiola has even been recently considered a supplement to be provided in military rations. The suggestion insinuates it may help provide troops with more energy and enhanced athletic ability, even mentioning the need for troops to be able to operate in harder environments (such as high altitudes).44 Other military manuscripts indicate Rhodiola may help troops improve short-term cognitive ability and work as an adaptogen to help with brain stresses. Several studies have found Rhodiola effective in being used as a stimulant, to reduce fatigue, to increase focus and attention span, as well as to increase work productivity.46 It has even been used to improve memory formation, memory recall, and learning.45

Not only have studies revealed an overall benefit/risk balance as being positive, but some studies have specifically mentioned that Rhodiola is effective in temporarily relieving symptoms of fatigue and weakness. It has been additionally indicated that Rhodiola helps with a number of cognitive cerebral functions including: associative thinking, concentration, perception and cognitive reflex improvements, problem solving and short-term memory.46 This makes Rhodiola a highly-influential adaptogen-nootropic for energy-improving supplements and formulae. It also suggests Rhodiola as being especially helpful in keeping the brain clear of extra daily stresses and improving Gf.

The Pirate Botanicals Pirate Blast formula uses Rhodiola.


5-Hydroxytryptophan (5-HTP) is naturally occurring, an amino acid, and a supplement. 5-HTP comes from the seeds of the Griffonia Simplicfolia plant and have been well-known in traditional African medicine. It is the immediate precursor for serotonin, and has been used in combination with other nootropics and herbs to promote peace and relaxation.47

5-HTP is one of the more serotonergic nootropics and has been studied numerous times in a large number of trials for its potent, relaxing properties. However, is typically considered most useful when combined with other nootropics or substances.48 One recent study suggests 5-HTP could have a significant impact on attention-span and memory formation.49

The power of being relaxed can go a long way, having real-world impacts in everyday life. For example, a student who is cognitively fatigued will exhibit poorer performance on a standardized test than a well-rested, relaxed student.51 Having a balanced brain is desirable, which means a healthy production of the appropriate neurotransmitters. 5-HTP has such a strong impact on the brain’s production of serotonin, making it a traditionally employed mood enhancer. Being a clinically effective serotonin precursor is likely its greatest value and also the reason it is used for brain-relaxation formulae.50 And it is easy to speculate that a relaxed decision making process can improve Gf.

The Pirate Botanicals Pirate Chill formula uses 5-HTP.


L-Theanine (aka γ-glutamylethylamide) is well-known for its neuroprotective properties in the brain.

L-Theanine is both a green tea component and a non-protein amino acid, which means it helps build proteins. It is typically used as a calming remedy and for strengthening the effects of other nootropics and herbs. This is because of Theanine’s power to increase GABA, serotonin and dopamine in the brain.52,53 GABA is well-understood to be a critical part of healthy neuronal function, the leaning process and memory. GABA is also important in the regulation of general cognition and neural development.54

L-theanine has also been used around the world in some of the most successful supplement and nootropics formulae for improving mood and promoting feelings of relaxation.53 In fact, the amazing calming effects of L-Theanine and its successful use around the world for adaptogenic and neuroprotective properties well justify its efficacy in many focus oriented-formulae. After all and as mentioned before, Fluid Intelligence potential is much higher when the brain is healthiest.

The Pirate Botanicals Pirate Chill formula uses L-Theanine.

Passion Flower

Passion Flower is often one of the most widely underestimated nootropic herbs. It is also known as Passiflora and has a rather extensive history of being cultivated and used around the world.55 Passion Flower has been traditionally used for thousands of years for its incredibly potent MAO inhibitor activity in the form of beta-carboline harmala alkaloids.56 MAOIs, or Monoamine oxidase inhibitors like Passion Flower, have been sought after for their anti-depressant properties and efficacy as therapeutic agents for various stress-inducing phobias (panic disorders, social phobias, etc.).57 In fact, many studies have revealed dramatic calming benefits from Passiflora extract trials in particular, and for a number of applications.56,58

how passion flower can help with fluid iq

Lower stress levels are notoriously associated with better testing scores, more efficient learning, and greater output at work. Passion Flower has become one of the more potent herbs found in nootropics stacks that focus on improving cognitive advantages due to its traditional use for reducing stress, fostering balanced thinking, improving spatial memory and favorably impacting neurotransmission.59

Additionally, GABA is a prominent ingredient in Passion Flower extract, which has been suggested to help boost cognitive function and the formation of memories.60,61 Basically, Passion Flower extract is a great nootropic for maintaining a balanced brain.

The Pirate Botanicals Pirate Chill formula uses Passion Flower.

Summary + Conclusion

Nootropics have been around as long as mankind, if not longer. There are many nootropics which have been used by cultures around the world for hundreds, sometimes thousands of years for their ability to provide the brain a boost of some kind. The research and studies on nootropics are constantly expanding. It is very common to use numerous nootropics together to achieve greater effects, although achieving a safe formula is still important too!

Pirate Botanicals nootropics supplements are 100 percent natural and use pharmacist-approved formulae. Piratall, Pirate Blast, and Pirate Chill are each designed to offer their own version of brain optimization. The above ingredients (and in which products they can be found) may help narrow down the most appropriate nootropics supplement choice for anyone. Remember, all Pirate Botanicals nootropics are considered a daily supplement and work best when used daily.

Disclaimer: These statements have not been approved by the FDA. None of this information is meant to substitute for a face-to-face consultation with a physician. Pirate Botanicals products are not meant to treat, cure, or diagnose any disease, illness, or condition.


1Jaeggi, S. M., Buschkuehl, M., Jonides, J., & Perrig, W. J. (2008). Improving fluid intelligence with training on working memory. Proceedings of the National Academy of Sciences of the United States of America, 105(19), 6829–6833.

2Cattell, R. B. (1971). Abilities: Their structure, growth, and action. New York: Houghton Mifflin. ISBN 0-395-04275-5

3Brown, R. E. (2016). Hebb and Cattell: The Genesis of the Theory of Fluid and Crystallized Intelligence. Frontiers in Human Neuroscience, 10, 606.

4Br J Educ Psychol. 2014 Dec;84(Pt 4):556-70. doi: 10.1111/bjep.12041. Epub 2014 Jun 9

5Cattell, R. B. (1963). Theory of fluid and crystallized intelligence: A critical experiment. Journal of Educational Psychology, 54, 1-22

6Malkova, L., Kozikowski, A. P., & Gale, K. (2011). The effects of huperzine A and IDRA 21 on visual recognition memory in young macaques. Neuropharmacology, 60(7-8), 1262–1268.

7Wu, C.-Y., Hu, H.-Y., Chow, L.-H., Chou, Y.-J., Huang, N., Wang, P.-N., & Li, C.-P. (2015). The Effects of Anti-Dementia and Nootropic Treatments on the Mortality of Patients with Dementia: A Population-Based Cohort Study in Taiwan. PLoS ONE, 10(6), e0130993.

8Allain, H., Akwa, Y., Lacomblez, L., Lieury, A., & Bentué-Ferrer, D. (2007). Impaired cognition and attention in adults: pharmacological management strategies. Neuropsychiatric Disease and Treatment, 3(1), 103–116

9Belsky, Janet K. (1990). The Psychology of Aging Theory, Research, and Interventions. Pacific Grove: Brooks/Cole Publishing Company

10Geary, David. (2009). The evolution of general fluid intelligence. Foundations in Evolutionary Cognitive Neuroscience. 22-56. 10.1017/CBO9780511626586.002

11Cattell, R. B. (1963). Theory of fluid and crystallized intelligence: A critical experiment. Journal of

Educational Psychology, 54 , 1–22

12Sahakian, B.J. and Morien-Zamir, S., (April 2015). Pharmacological cognitive enhancement: treatment of neuropsychiatric disorders and lifestyle use by healthy people. Lancet Psychiatry. 2015 Apr;2(4):357-62. doi: 10.1016/S2215-0366(15)00004-8. Epub 2015 Mar 31

13Kumar, V., Khanna, V.K., Seth, P.K., Singh, P.N., and Bhattacharya, S.K., (May 2002). Brain Neurotransmitter receptor binding and nootropic studies on Indian Hypericum perforatum linn. Phytother Res.. 16(3):210-6

14Ling, I., et al., (Oct 5, 2015). A Novel GABA(A) alpha 5 receptor inhibitor with therapeutic potential. Retrieved from US National Library of Medicine ( on 09-21-18

15Frati, P., Kyriakou, C., Del Rio, A., Marinelli, E., Vergallo, G. M., Zaami, S., and Busardo, F. P., (2015). Smart Drugs and Synthetic Androgens for Cognitive and Physical Enhancement: Revolving Doors of Cosmetic Neurology. Current Neuropharmacology. 13(1)

16Giurgea C (1972). Vers une pharmacologie de l’active integrative du cerveau: Tentative du concept nootrope en psychopharmacologie. Actual Pharmacol (Paris-released journal). Issue 25: 115–56

17Zaval, L., Li, Y., Johnson, E. J., and Weber, E. U., (2015). Aging and Decision Making: Complementary Contributions of Fluid and Crystallized Intelligence to Decision Making Across the Life Span. Empirical and Applied Perspectives. Chapter 8, pp149-167

18Squire, L. R., et al. (2009). Encyclopedia of Neuroscience. Elsevier. ISBN 978-0-08-045046-9

19Paul, E. J., Larsen, R. J., Nikolaidis, A., Ward, N., Hillman, C. H., Cohen, N. J., Kramer, A. F., and Barbey, A. K., (August 15, 2016). Dissociable Brain Biomarkers of Fluid Intelligence. NeuroImage, Vol 137. pp 201-210

20Filickova, M., Ropovik, I., Bobakova, M., and Kovalcikova, I., (2015). The Relationship Between Fluid Intelligence and Learning Potential: Is There An Interaction With Attentional Control?. De Gruyter. JoP 6(1): 25-41

21BBovaird J.A. (2010) Gf-Gc Model of Intelligence. In: Clauss-Ehlers C.S. (eds) Encyclopedia of Cross-Cultural School Psychology. Springer, Boston, MA

22Teles-Grilo Ruivo, L. M., Baker, K. L., Conway, M. W., Kinsley, P. J., Gilmour, G., Phillips, K. G., … Mellor, J. R. (2017). Coordinated Acetylcholine Release in Prefrontal Cortex and Hippocampus Is Associated with Arousal and Reward on Distinct Timescales. Cell Reports, 18(4), 905–917.

23Haam, J., & Yakel, J. L. (2017). Cholinergic modulation of the hippocampal region and memory function. Journal of Neurochemistry, 142(Suppl 2), 111–121.

24Brekhman, I. I., and Dardymov, I. V., (April 1969). New Substances of Plant Origin Which Increase Nonspecific Resistance. Annual Review of Pharmacology. Vol. 9, pp 419-430

25Tassell, M. C., Kingston, R., Gilroy, D., Lehane, M., & Furey, A. (2010). Hawthorn (Crataegus spp.) in the treatment of cardiovascular disease. Pharmacognosy Reviews, 4(7), 32–41.

26Winston, D., and Maimes, S., (2007). Adaptogens: Herbs for Strength, Stamina, and Stress Relief. Healing Arts Press. Rochester, Vermont. Pp 17-84

27Załuski, D., Olech, M., Galanty, A., Verpoorte, R., Kuźniewski, R., Nowak, R., & Bogucka-Kocka, A. (2016). Phytochemical Content and Pharma-Nutrition Study on Eleutherococcus senticosus Fruits Intractum. Oxidative Medicine and Cellular Longevity, 2016, 9270691.

28Abbai, R., Mathiyalagan, R., Markus, J., Kim, Y.-J., Wang, C., Singh, P., … Yang, D. C. (2016). Green synthesis of multifunctional silver and gold nanoparticles from the oriental herbal adaptogen: Siberian ginseng. International Journal of Nanomedicine, 11, 3131–3143.

29Lima, N. da S., Numata, E. de P., Mesquita, L. M. de S., Dias, P. H., Vilegas, W., Gambero, A., & Ribeiro, M. L. (2017). Modulatory Effects of Guarana (Paullinia cupana) on Adipogenesis. Nutrients, 9(6), 635.

30Moustakas, D., Mezzio, M., Rodriguez, B. R., Constable, M. A., Mulligan, M. E., & Voura, E. B. (2015). Guarana Provides Additional Stimulation over Caffeine Alone in the Planarian Model. PLoS ONE, 10(4), e0123310.

32Jin, M.-J., Yoon, C.-H., Ko, H.-J., Kim, H.-M., Kim, A.-S., Moon, H.-N., & Jung, S.-P. (2016). The Relationship of Caffeine Intake with Depression, Anxiety, Stress, and Sleep in Korean Adolescents. Korean Journal of Family Medicine, 37(2), 111–116.

33Eugene van Tamelen, Maurice Shamma, Albert Burgstahler, Joseph Wolinsky, Rudolph Tamm, and Paul Aldrich, (1958). The Total Synthesis of Yohimbine. Journal of the American Chemical Society. Volume 80 (18).

34Tejada, S., Kim, N. N., Goldstein, I., and Traish, A. M., (May 2, 2000). Regulation of Pre-Synaptic Alpha Adrenergic Activity in the Corpus Cavernosum. IJIR. 12(S20-S25).

35O’Donnell, J., Zeppenfeld, D., McConnell, E., Pena, S., & Nedergaard, M. (2012). Norepinephrine: A Neuromodulator That Boosts the Function of Multiple Cell Types to Optimize CNS Performance. Neurochemical Research, 37(11), 2496–2512.

36R.b. Jiofack Tafokou. Pausinystalia johimbe. pp 516-519 in Timbers Volume 2; Volume 7 of Plant Resources of Tropical Africa. Eds. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A., G.J.H Grubben. PROTA Foundation, 2012. ISBN 9789290814955

37Anadon, A., Martinez-Larranaga, M. R., Ares, I., and Martinez, M. A., (February 19, 2016). Interactions Between Nutraceuticals/Nutrients and Therapeutic Drugs. Nutraceuticals: Efficacy, Safety and Toxicity. Pages 855-873.

38Gonzales, G. F. (2012). Ethnobiology and Ethnopharmacology of Lepidium meyenii (Maca), a Plant from the Peruvian Highlands. Evidence-Based Complementary and Alternative Medicine : eCAM, 2012, 193496.

39Rubio, J., Qiong, W., Liu, X., Jiang, Z., Dang, H., Chen, S.-L., & Gonzales, G. F. (2011). Aqueous Extract of Black Maca (Lepidium meyenii) on Memory Impairment Induced by Ovariectomy in Mice. Evidence-Based Complementary and Alternative Medicine : eCAM, 2011, 253958.

40Stone, M., Ibarra, A., Roller, M., Zangara, A., and Stevenson, E.J. (2009) ‘A pilot investigation into the effect of maca supplementation on physical activity and sexual desire in sportsmen’, Journal of Ethnopharmacology, 126 (3), pp. 574-576.

41Stojanovska, L., Law, C., Lai, B., Chung, T., Nelson, K., Day, S., Apostolopoulos, V., and Haines, C., (February 2015). Maca Reduces Blood Pressure and Depression, in a Pilot Study in Postmenopausal Women. Climacteric. DOI: 10.3109/13697137.2014.929649. Retrieved on September 24, 2018.

42Rubio, Julio & Yucra, Sandra & Gasco, Manuel & Gonzales, Gustavo. (2011). Doseresponse effect of black maca (Lepidium meyenii) in mice with memory impairment induced by ethanol. Toxicology mechanisms and methods. 21. 628-34. 10.3109/15376516.2011.583294.

43Popenoe, H., (1989). Little-Known Plants of the Andes with Promise for Worldwide Cultivation. National Academy Press. Washington D.C.. Chapter 8. Pp 56-63.

44Greenwood, MRC, (June 9, 2008). Use of Dietary Supplements by Military Personnel. Institute of Medicine of the National Academies. Chapter 1. Pp 30-31.

45Erdman Jr, J., (December 9, 2005). Nutrient Composition of Rations for Short-Term, High-Intensity, Combat Operations. Institute of Medicine of the National Academies. Pp 290-306.

46HMPC, (March 12, 2012). Assessment Report on Rhodiola Rosea L., Rhizoma et Radix. European Medicines Agency: Science, Medicines and Health. Retrieved from EMA Europa ( on September 24, 2018.

47Hinz, M., Stein, A., & Uncini, T. (2012). 5-HTP efficacy and contraindications. Neuropsychiatric Disease and Treatment, 8, 323–328.

48Jacobsen, J. P. R., Krystal, A. D., Krishnan, K. R. R., & Caron, M. G. (2016). Adjunctive 5-hydroxytryptophan slow-release for treatment-resistant depression: Clinical and pre-clinical rationale. Trends in Pharmacological Sciences, 37(11), 933–944.

49Weinberg-Wolf, H., Fagan, N. A., Anderson, G. M., Tringides, M., Dal Monte, O., and Chang, S. W. C., (January 30, 2018). The Effects of 5-Hydroxytryptophan on Attention and Central Serotonin Neurochemistry in the Rehsus Macaque. Neuropsychopharmacology. Volume 43. Pp 1589-1597.

50Birdsall TC. 5-Hydroxytryptophan: a clinically-effective serotonin precursor. Altern Med Revised Edition: 1998. Volume 3(4). Pp 271-280.

51Sievertsen, H. H., Gino, F., & Piovesan, M. (2016). Cognitive fatigue influences students’ performance on standardized tests. Proceedings of the National Academy of Sciences of the United States of America, 113(10), 2621–2624.

52Kapalka, G. M., (2010). Nutritional and Herbal Therapies for Children and Adolescents. Practical Resources for the Mental Health Professional. Chapter 8. Pp 219-256.

53Kapalka, G. M., (2010). Nutritional and Herbal Therapies for Children and Adolescents. Practical Resources for the Mental Health Professional. Chapter 7. Pp 191-218.

54Govindpani, K., Calvo-Flores Guzmán, B., Vinnakota, C., Waldvogel, H. J., Faull, R. L., & Kwakowsky, A. (2017). Towards a Better Understanding of GABAergic Remodeling in Alzheimer’s Disease. International Journal of Molecular Sciences, 18(8), 1813.

55Krosnick, S. E., Porter-Utley, K. E., MacDougal, J. M., Jorgensen, P. M., and McDade, L. A., (September, 2013). New Insights into the Evolution of Passiflora subgenus Decaloba (Passifloraceae): Phylogenetic Relationships and Morphological Synapomorphies. Systematic Botany. Volume 38(3). Pp 692-712. DOI: 10.1600/036364413X670359

56Akhondzadeh, S., Naghavi, H. R., Vazirian, M., Shayeganpour, A., Rashidi, H., and Khani, M., (January 12, 2002). Passionflower in the treatment of generalized anxiety: a pilot double‐blind randomized controlled trial with oxazepam. Journal of Clinical Pharmacy and Therapeutics. Volume 26(5). Pp 363-367.

57Cristancho, M. A., O’reardon, J. P., Thase, M. E., (November 20, 2012). Atypical Depression in the 21st Century: Diagnostic and Treatment Issues Psychiatric Times. Volume 28(1).

58Kaviani, N., Tavakoli, M., Tabanmehr, M., & Havaei, R. (2013). The Efficacy of Passiflora Incarnata Linnaeus in Reducing Dental Anxiety in Patients Undergoing Periodontal Treatment. Journal of Dentistry, 14(2), 68–72.

59Jawna-Zboinska, K., Blecharz-Klin, K., Joniec-Maciejak, I., Wawer, A., Pyrzanowska, J., Piechal, A., Mirowska-Guzel, D., and Widy-Tyszkiewicz, E., (May, 2016). Passiflora incarnata L. Improves Spatial Memory, Reduces Stress, and Affects Neurotransmission in Rats. Phytother Res. DOI: 10.1002/ptr.5578

60Elsas, S.-M., Rossi, D. J., Raber, J., White, G., Seeley, C.-A., Gregory, W. L., … Soumyanath, A. (2010). Passiflora incarnata L. (Passionflower) extracts elicit GABA currents in hippocampal neurons in vitro, and show anxiogenic and anticonvulsant effects in vivo, varying with extraction method. Phytomedicine : International Journal of Phytotherapy and Phytopharmacology, 17(12), 940–949.

61Goldman, B., and Yoon, J. H., (November 15, 2016). More GABA in one brain region linked to better working memory. Stanford Medicine News Center. Accessed from Stanford BIO-X ( on September 25, 2018.