title_body: What are the side effects of drinking too much coffee?
upvoted_answer: Caffeinated beverages like coffee and soft drinks give short bursts of energy, but can actually cause fluid loss. Caffeine has been shown to temporarily raise blood pressure, and reduces blood flow to inactive limbs.
  Like many drugs, caffeine is chemically addictive and recent publication of Diagnostic and Statistical Manual of Mental Disorders (DSM), caffeine withdrawal was finally included as a mental disorder for the first time.
  Soon after you drink coffee (containing caffeine), it’s absorbed through the small intestine and dissolved into the bloodstream and it’s able to penetrate the blood-brain barrier and enter the brain.
  Regular ingestion of the drug (i.e. coffee/tea, soda or energy drinks) alters your brain’s chemistry and physical characteristics actually change over time, leading to fatigue, headaches and nausea if you try to quit. However, compared to many drug addictions, the effects are relatively short-term.
  Few quotes from Daily Mail:
  
  Large amounts of caffeine can cause heart palpitations, fits and even death, as well as raising the risk of Type 2 diabetes.
  Heavy consumption has also been linked to a greater risk of depression, addiction and alcohol dependency.
  Energy drinks could be more likely to cause a caffeine overdose because they can be drunk quickly, unlike hot drinks like tea or coffee, the Energy Drink Consumption in Europe study said.
  Several deaths worldwide have been linked to excessive consumption of energy drinks, although scientists say more research is needed to prove a link.
  Recommended maximum caffeine intake is about 400mg per day – equivalent to around five cups of filter coffee.
  
  'Reproductive-aged women (⩽ 300 mg caffeine per day) and children are ‘at risk’ subgroups who may require specific advice on moderating their caffeine intake', study said.
  On Live Science we can read:
  
  Coffee drinking could lead to a mental disorder. If you experience
  five or more symptoms, such as red face, nervousness and restlessness,
  during or right after your cup of Joe, you may be diagnosed with
  coffee intoxication.
  
  According to a new edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5), excessive caffeine intake can lead to a condition known as “caffeine intoxication,”.
  In other words, caffeine withdrawal is now a recognized disorder, and is listed in the DSM-5.
  
  “Caffeine is a drug, a mild stimulant, which is used by almost
  everybody on a daily basis,” said Dr. Charles O’Brien, who chairs the
  Substance-Related Disorder Work Group for DSM-5 (via New York Post).
  “But it does have a letdown afterwards. If you drink a lot of coffee,
  at least two or three [236 ml] cups at a time, there will be a rebound
  or withdrawal effect.”
  
  Here are top 10 caffeine withdrawal symptoms:
  
  Headache
  Sleepiness
  Irritability
  Lethargy
  Constipation
  Depression
  Muscle Pain/Stiffness
  Lack of Concentration
  Flu-like symptoms
  Insomnia
  
  In rare cases when consumed at high enough doses, caffeine can kill.
  
  
  In the world's most expensive Starbucks coffee featuring 60 espresso shots, according to my calculations, there is over 9000mg (150x60) of caffeine content, comparing to recommended maximum caffeine intake of 400mg per day (equivalent to over 100 cups of filtered coffee). So drinking it will end up with headache, fast heartbeat, heart palpitations and even death, so it require emergency care as soon as possible.
  Here is SAMHSA data of emergency department visits related to misuse of energy drinks (energy drinks can be looked at as caffeine) and it is really alarming:
  
  SAMHSA report puts it:
  
  Large amounts of caffeine can cause adverse effects such as insomnia,
  nervousness, headache, fast heartbeat, and seizures that are severe
  enough to require emergency care.
  
  
  Related:
  
  (article) Sales of sugar and caffeine laden energy drinks should be restricted as they 'pose a danger' to children at Daily Mail
  What's the minimum recommended age for drinking a coffee?
  This Is How Your Brain Becomes Addicted to Caffeine at Smithsonian
  What Caffeine Actually Does to Your Brain at Life Hacker
  (study) Effects of Caffeine on Human Health, P. Nawrot, S. Jordan, J. Eastwood, J. Rotstein, A. Hugenholtz and M. Feeley, Food Additives and Contaminants, 2003, Vol. 20, No. 1, pg. 1-30.
  (study) Actions of Caffeine in the Brain with Special Reference to Factors That Contribute to Its Widespread Use
  Caffeine Withdrawal Is Now a Mental Disorder at Time
  (book) Buzz: The Science and Lore of Alcohol and Caffeine by Stephen Braun