400 mg per day of caffeine is considered safe for most healthy adults – some textbooks state that caffeine is a mild euphoriant, others state that it is not a euphoriant.
An average cup of black tea with milk contains around 47 mg of caffeine; the average caffeine content of an 8-oz, brewed cup of coffee is 95 mg, a single espresso or espresso-based drink contains 63 mg, and decaf coffee contains about 3 mg.
Caffeine-containing drinks, such as coffee and tea are consumed globally in high volumes; in 2020, almost 10 million tonnes of coffee beans were consumed globally and the consumption volume of tea in India was approximately one billion kilograms.
Caffeine is a central nervous system (CNS) stimulant, it is the world’s most widely consumed psychoactive drug.
According to a 2011 literature review, caffeine use is positively associated with anxiety and panic disorders. At high doses, typically greater than 300 mg, caffeine can both cause and worsen anxiety – for some people, discontinuing caffeine use can significantly reduce anxiety. In moderate doses, caffeine has been associated with reduced symptoms of depression and lower suicide risk.
A psychoactive drug is a chemical substance that changes nervous system function and results in alterations in perception, mood, consciousness, cognition, or behavior.
Stimulants are a class of drugs that “stimulate” the body’s central nervous system, which includes the brain and spinal cord.
Stimulants are used in impulse control disorders such as ADHD and off-label in mood disorders such as major depressive disorder to increase energy, focus and elevate mood; they increase the levels of catecholamines—a family of brain chemicals that includes dopamine, these chemicals are used in the brain processes to signal reward and motivation, by increasing catecholamine levels, stimulants can temporarily increase a person’s energy level and alertness. Stimulants may also cause other changes in the body.
High caffeine consumption in energy drinks (At least 1 liter or 320 mg of caffeine) was associated with short-term cardiovascular side effects including hypertension, prolonged QT interval and heart palpitations. These cardiovascular side effects were not seen with smaller amounts of caffeine consumption in energy drinks (less than 200 mg).
(Ref. Wikipedia, statista.com, healthline.com, bbcgoodfood.com & headsup.scholastic.com)