Coffee is one of the most popular beverages in the world, and 85 percent of Americans drink at least one cup per day. But with the keywords being “at least,” it’s safe to assume that by 5 p.m., many of these people are well past two cups, the Medical Daily reported.  Though coffee has been touted for several health benefits, like preventing liver cancer, drinking too much can be somewhat harmful too, and in ways you probably didn’t expect — or notice — such as…

Anxiety and psychosis

Coffee’s effects on the brain are actually quite profound. The science behind caffeine’s pick-me-up power comes from its ability to trick the brain into thinking it's another molecule called adenosine, which tells the brain when it’s time to sleep. In doing so, it potentiates the release of dopamine and adrenaline, among other stimulants, which keep a person awake, attentive, and in a better mood. However, that’s after, say, one to two cups, depending on how much caffeine they hold. 

People who consume more than that may begin to experience too much of caffeine’s stimulant effect. A report in the journal Advances in Psychiatric Treatment notes that symptoms of excessive caffeine ingestion and psychiatric disorders often overlap because they “may both have a basis in overactivity of the sympathetic nervous system.” 

In turn, the coffee drinker becomes erratic, nervous, and irritable. Sometimes, these effects may go so far that they can be compared to symptoms of psychosis. 

Hearing things

Caffeine is, after all, a psychoactive drug. The Mayo Clinic suggests anyone who drinks about 500 milligrams of caffeine a day, or five cups, cut back. It’s probably a good idea. A study from La Trobe University in Melbourne, Australia, found five cups was exactly the amount that made people hear the song “White Christmas” by Bing Crosby, even though they were actually listening to plain white noise.

Professor Simon Crowe, a co-author of the study, said that they told the participants that “within the white noise, there may be parts of the song ‘White Christmas,’ and if you hear it, press a button,” according to the Medical Daily with reference to Daily Mail. “We didn’t include ‘White  Christmas’ in the white noise,  but found that more people  who were very stressed, and had high levels of caffeine thought they heard the song.”

The jitters: Muscle spasms and restlessness

In the same way that caffeine stimulates the brain, the stimulant effects translate through the central nervous system (CNS) into the muscles and heart, affecting motor activity as well.

According to the National Institutes of Health, caffeine is among the top three causes of eye twitches. These twitches are characterized by repeated and uncontrollable spasms of the upper eyelid, a sensitivity to light, and blurry vision.

Osteoporosis

The bone disease that affects one in two women and one in four men in the U.S. is caused, in part, by a deficiency of calcium in a person’s body. As the bone deteriorates, microscopic pores on its surface get bigger, thus making it more fragile.

Some scientists suspect that the condition may develop as a result of too much caffeine. Although the findings from multiple studies have been inconclusive, they’re based on the idea that coffee can hinder the digestive tract’s ability to absorb calcium, says Dr. Robert H. Shmerling, of Harvard Medical School.

Mayo Clinic advises everyone to drink, at most, 400 milligrams of caffeine per day, or an average of four cups. But with varying levels of caffeine in each cup of coffee, it might be best to just stick to one or two.