l-theanine (Examine.com) is occasionally mentioned on Reddit or Imminst or LessWrong33 but is rarely a top-level post or article; this is probably because theanine was discovered a very long time ago (>61 years ago), and it’s a pretty straightforward substance. It’s a weak relaxant/anxiolytic (Google Scholar) which is possibly responsible for a few of the health benefits of tea, and which works synergistically with caffeine (and is probably why caffeine delivered through coffee feels different from the same amount consumed in tea - in one study, separate caffeine and theanine were a mixed bag, but the combination beat placebo on all measurements). The half-life in humans seems to be pretty short, with van der Pijl 2010 putting it ~60 minutes. This suggests to me that regular tea consumption over a day is best, or at least that one should lower caffeine use - combining caffeine and theanine into a single-dose pill has the problem of caffeine’s half-life being much longer so the caffeine will be acting after the theanine has been largely eliminated. The problem with getting it via tea is that teas can vary widely in their theanine levels and the variations don’t seem to be consistent either, nor is it clear how to estimate them. (If you take a large dose in theanine like 400mg in water, you can taste the sweetness, but it’s subtle enough I doubt anyone can actually distinguish the theanine levels of tea; incidentally, r-theanine - the useless racemic other version - anecdotally tastes weaker and less sweet than l-theanine.)

l-Theanine – A 2014 systematic review and meta-analysis found that concurrent caffeine and l-theanine use had synergistic psychoactive effects that promoted alertness, attention, and task switching;[29] these effects were most pronounced during the first hour post-dose.[29] However, the European Food Safety Authority reported that, when L-theanine is used by itself (i.e. without caffeine), there is insufficient information to determine if these effects exist.[34]
Directions	—	as a dietary supplement take 2 veggie capsules once a day . For best results take 20-30 min before a meal with an 8oz. Glass of water or as directed by your healthcare professional.	As a dietary supplement take two (2) veggie capsules once a day. For best results take 20-30 minutes before a meal with an 8oz. glass of water or as directed by your healthcare professional.	—	Suggested Use: As a dietary supplement, adults take one (1) capsule per day. Do not exceed 2 capsules per day.	—

Alex's sense of who uses stimulants for so-called "non-medical" purposes is borne out by two dozen or so scientific studies. In 2005 a team led by Sean Esteban McCabe, a professor at the University of Michigan, reported that in the previous year 4.1% of American undergraduates had taken prescription stimulants for off-label use - at one school the figure was 25%, while a 2002 study at a small college found that more than 35% of the students had used prescription stimulants non-medically in the previous year.
A common dose for this combination is 500 milligrams per day of Lion’s Mane, 240 milligrams per day of Ginkgo Biloba, and 100 milligrams twice per day of Bacopa Monnieri. Consider buying each ingredient in bulk to have stock and experiment with. If you are not experiencing positive results after 12 weeks, try adjusting the dosages in small increments. For example, you can start by adjusting Bacopa Monnieri to 150 milligrams twice per day for a couple weeks. Be patient: the end result is worth the trial and error.
But before you go lock yourself in a dark, quiet room in order to prevent this overburden on your brain, you should know that there are scientifically researched compounds designed to amplify cognitive function and help your brain deal with this excess load, or simply get you through a period of sleep deprivation, increased creativity or work demands, the need to pull an all-nighter or an intense bout of work or study.
The most common front-line of treatment for ADHD is medication and cognitive behavioural therapy (CBT). Prescriptions for ADHD drugs such as Ritalin, have doubled to 922,000 a year in the last decade, and whilst it offers symptom management for many, it has also been found to have significant negative side effects such as weight loss, liver toxicity, and suicidal thoughts, and in the short term may suppress pubertal growth. The aetiology of ADHD is multifactorial, meaning that there are varying influencing factors that drive the symptoms. This is perhaps why this condition has been hard to study and find effective treatment for.

From the standpoint of absorption, the drinking of tobacco juice and the interaction of the infusion or concoction with the small intestine is a highly effective method of gastrointestinal nicotine administration. The epithelial area of the intestines is incomparably larger than the mucosa of the upper tract including the stomach, and the small intestine represents the area with the greatest capacity for absorption (Levine 1983:81-83). As practiced by most of the sixty-four tribes documented here, intoxicated states are achieved by drinking tobacco juice through the mouth and/or nose…The large intestine, although functionally little equipped for absorption, nevertheless absorbs nicotine that may have passed through the small intestine.
[…] The 7 Best Brain Boosting Supplements | Live in the Now … – While under estimated in the brain health arena, adequate vitamin C is associated with a 20% reduction in risk of Alzheimer’s … Gingko Biloba, Phosphatidyl Serine and Coenzyme Q10. Opt for the best brain supplements and stay fit with an active brain. You should be very careful while … […]
Microdosing with Iboga: Native to the rainforests in Central Africa, Iboga is an evergreen shrub, with high concentrations found in the root bark. It has a rich history amongst practitioners in the indigenous Bwiti religion in Africa and has recently found its way into Western practices, primarily for extremely effective therapy for drug addictions, but also for physical energy, cognitive performance in smaller microdoses, and a surge in positive emotions (See additional studies here and here.).  To microdose with Iboga, you will want to find it in tincture or root bark form (the root bark form is typically encapsulated). If using a tincture, find a source that has the root bark extracted into its purest form, combined with Iboga alkaloids, which keeps the full spectrum of the plant untouched. Just a single drop of an Iboga tincture equates to about 0.5 milligrams and suffices as a microdose. For the root bark of Iboga, a dose of 300-500 milligrams is also an effective dose. I’ve personally found Iboga to be most useful prior to a workout or an effort that combines both brain and body demands, such as tennis or basketball – but it makes you hyperactive and jittery if taken prior to a day of desk work. This makes sense when you consider that African tribes traditionally whipped themselves into a frenzied pre-battle state on Iboga.
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.
Amphetamine – systematic reviews and meta-analyses report that low-dose amphetamine improved cognitive functions (e.g., inhibitory control, episodic memory, working memory, and aspects of attention) in healthy people, and in individuals with ADHD.[21][22][23][25] A 2014 systematic review noted that low doses of amphetamine also improved memory consolidation, in turn leading to improved recall of information in non-ADHD youth.[23] It also improved task saliency (motivation to perform a task) and performance on tedious tasks that required a high degree of effort.[22][24][25]