Psychology 2020A/B Study Guide - Final Guide: Kola Nut, Xanthine, Theobromine
27 Apr 2018
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Psych 2020 final exam notes
Caffeine
• Worlds most commonly used drug for psychoactive effects
• Every day up to % of the world’s population consumes something with caffeine
• Regular size cup of coffee contains about 100mg of caffeine
• Caffeine is just one of several methylxanthines
• Theophylline and theobromine are often found in combination with caffeine
• Methylxanthines occur in over 60 species of plants
• In plants xanthines serve a protective purpose when insects eat xanthine containing
plant material there is increased production of octopamine an excitatory
neurotransmitter which leads to overexcitation and death
• Plants that contain methylxanthines are coffee, tea, yarba mate, guarana, kola nut, and
cacao
• Yerba mate is used by steeping the leaves similar to tea and guarana is used by brewing
the roasted berries like coffee
• Guarana also contains theophylline and theobromine and is found in a variety of energy
drinks
• Tea is the earliest caffeine containing beverage used for psychostimulating effects
• Earliest mention of tea from China in 2737 BC, the Chinese emperor Shen Nung was
boiling water and a tea leaf fell in and he liked it
• Tea drinking was introduced in Europe in the ’s when European traders returned
from forays to the Far East but only gained popularity in England and Russia
• To meet demands for tea the British forced the Chinese to accept opium in payment for
tea which was one of the reasons for the Opium wars in the ’s
• First tea shipment to Canada was imported by the (udson’s Bay Company in
• Caffeine content of tea varies but approx. 50mg per standard cup
• Tea also contains theophylline which is equipotent to caffeine as a stimulant
• Legend of discovery of coffee is that an Ethiopian or Yemenite goatherder noticed his
goats in a state of behavioral excitation and traced it to berries they had eaten, sampled
them and brought them to the temple
• Early use of coffee berries were chewed and later the fermented juice was drunk
• Later still coffee bean roasting and grinding spread in Africa and the Middle East
• Sporadic attempts to ban coffee on religious grounds because coffee was considered to
be an intoxicant
• Sultan Murad IV closed down all coffeehouses in 1633 and if found 2x in a coffeehouse
sewn in a leather bag and tossed in the river
• Coffee was known in Europe as the wine of islam
• Coffeehouses began to appear in England in the mid 1600s and there also were attempts
to ban with main concerns over political dissent
• Popular nickname for coffeehouses was penny universities to reflect the belief that
coffeehouses had the intellectual atmosphere of universities but much cheaper
• 100mg is typical value of a standard cup of coffee but amount of caffeine varies on how
it’s made and the type of bean used
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• Caffeine is the only xanthine found in coffee
• Common source of caffeine in North America are cola drinks
• Estimated Canadians drink about 85 liters per day and US is world leader at 216 liters
per day
• Almost all of the caffeine in cola drinks is added since the kola nut used in the
production of cola drinks contains very little caffeine
• Typical can of cola contains around 40mg of caffeine
• Caffeine content of energy drinks often not much higher than a standard cup of coffee
e.g. red bull-80, jolt-280
• Energy drinks lead to acute improvements in cognitive performance and mood,
primarily due to caffeine
• Pure caffeine sold in over the counter medications like anti-sleeping pills and some pain
relievers and cold remedies contain caffeine
• Enough caffeine in a bottle of caffeine tablets to be fatal
• Number of caffeine containing chewing gums, mints, and candies like stay alert or holt
gum dangerous because of reports of caffeine intoxication in young children
• Primary source of methylxanthine theobromine is chocolate
• Chocolate is made from cocoa pods from cocoa trees and was used as a drink by the
Aztecs when the Spanish came to South and North America
• Chocolate was given as betrothal gifts by Spanish princesses which may be the origin of
chocolate with romance and chocolate was considered a symbol of wealth
• Chocolate isn’t rich in caffeine but is the main source of theobromine, mg in milk
chocolate, 20mg/g cocoa powder, dark chocolate 180mg
• Effects of theobromine similar to caffeine but drug is only 1/10 as potent as caffeine or
theophylline but theobromine in chocolate can be fatal if enough is ingested by dogs or
horses
• Caffeine was isolated from coffee in 1820 and from tea in 1827
• Pure caffeine is a white powder resembling baking powder and is extremely bitter to
the taste
• Caffeine is rapidly absorbed in the gastrointestinal tracts and significant blood levels are
reached in 30-60 min following ingestion with peak concentration in 1hr
• Half-life of caffeine is about 5 hours but increased to 10hrs near end of pregnancy
• Caffeine is metabolized in the liver and excreted 9-% metabolized
• Enzyme that metabolizes caffeine is inhibited by certain selective serotonin reuptake
inhibitors and this can result in an increased probability of adverse reactions to caffeine
• Smokers metabolize caffeine twice as fast as nonsmokers
• Pregnancy and contraceptives slow down caffeine metabolism
• Caffeine and other methylxanthines are antagonists at adenosine receptors in both the
periphery and CNS
• Normally adenosine acts to reduce the release of many classes of neurotransmitters and
generally suppresses neural activity
• Effects produced when adenosine occupies its receptors include: sleepiness, dilation of
blood vessels, constriction of bronchial passageways, and reducing the body’s reaction
to stress
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• Caffeine has a molecular structure similar to adenosine and will occupy adenosine
receptors but produce no neurochemical activity and blocks adenosine from occupying
the receptors preventing its effects
• Effects of adenosine is neural slowing and relaxation so blocking of effects leads to
neural excitation: pupil dilation, opening of airways, increased heart rate, release of
sugar into blood for energy, decreased blood flow to the periphery, and increased
muscle tone
• Caffeine leads to constriction of blood vessels in the brain which may relieve headaches
Psychological effects of caffeine
- Elevation of subjective mood
- Increased mental alertness reflected in reduced reaction times and slowing of
detrimental effects of fatigue and boredom on vigilance tasks
- Increased wakefulness and restlessness
- Decreased appetite
- Decreased quality of sleep
- Caffeine does not counteract the effects of alcohol
- Heartburn due to relaxation of esophageal sphincter
- Increased urinary excretion of calcium and inhibits absorption of calcium from diet
increasing risk of osteoporosis and bone fractures in elderly particularly women
- Lethal dose for adults is 200mg/kg
Consumption of large amounts of caffeine may lead to acute caffeine intoxication or caffeinism
Most typical estimate for amount of caffeine likely to produce acute intoxication is 600mg
Diagnostic criteria for caffeine-induced disorder in DSM-V:
a. Recent consumption of caffeine usually in excess of 250mg
b. Demonstration of 5 or more of the following signs during or shortly after caffeine use:
restlessness, excitement, insomnia, flushed face, diuresis, muscle twitching, tachycardia,
psychomotor agitation etc.
c. Above symptoms cause clinically significant distress or impairment in social,
occupational areas
d. Symptoms are not due to a general medical condition and aren’t better accounted for by
another mental disorder
DSM-V recognizes caffeine-induced disorder but no Caffeine use disorder
• Studies have shown tolerance to many but not all effects of caffeine
• Tolerance develops to most cardiovascular effects, locomotor stimulating effect, and
many of the emotional/mood effects with conflicting reports on tolerance to anti-sleep
effects
• Occurrence of tolerance usually indicates physical dependence will develop but this
isn’t the case for caffeine
• First systematic study of caffeine withdrawal was conducted by Dresibach and Pfeiffer
(1943) and withdrawal symptoms noticed were fatigue, disinclination to work, mental
depression, and headache
Other withdrawal symptoms include: weariness, apathy, weakness, drowsiness, anxiety,
decreased motor behavior, increased muscle tension, and tremor, nausea, vomiting and flu-like
feelings
• Withdrawal symptoms generally begin about 12-24 hours after cessation of caffeine
consumption, peak after 24-48 hours and are gone by one week
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