To some, drinking coffee is simply a habit passed on from their parents and old Folger's commercials. To others, coffee is essentially just another warm beverage enjoyed on a cold winter's day.
In my life, coffee is a gift and a curse, a euphoric elixir and a nerve-bending brew. One day it will provide a burst of energy known only to superheroes, where other times it will shape-shift productive afternoons into unnecessarily anxiety-filled workdays.
I know -- I should probably be sans-caffeine. But while I have my half-full extra large coffee in hand (only caffeine can make an optimist out of me), let us delve into this popular beverage and examine the evidence surrounding its health benefits and risks.
Caffeine, the main psycho-stimulant found in your morning's pot of java, is absorbed through your intestines and transported to your brain well within an hour of ingestion. The primary mechanism of action of caffeine is in its physical structure: It operates by mimicking another chemical called adenosine and thereby disrupts it's normal function in the brain.
Adenosine acts like mercury in a thermometer, only it gauges brain cell energy rather than heat. Adenosine levels in your central nervous system rise through the day as your cells use up energy and declines during sleep as your brain recharges. 
Thus, large adenosine concentrations built up in the brain indirectly contribute to that hangdog, droopy-eyed look we all know and love after a long day at work.
So caffeine, acting as an adenosine mimicker, acts to block adenosine by clogging up adenosine receptors in the brain. What happens next? The brain, falsely sensing low levels of adenosine, gets duped into thinking it should continue expending cellular energy rather than conserving it. This biochemical beguilement results in the feeling of vigor rather than the appropriate physiologic sensation of fatigue.
Sounds like a damn good drug to me. And much of the research behind caffeine agrees.
Why You Should Embrace The Bean
Caffeinated beverages such as your morning cup o' joe have been associated with a wide array of beneficial effects on the human body:
Alertness -- A strong cup of coffee can raise alertness and reduce the sensation of fatigue. This may be especially important in certain populations such as night-shift workers, jet-lagged travelers, and individuals suffering from ADHD. 
Headache -- This one is tricky. Caffeine, in combination with Tylenol or aspirin, has been demonstrated to relieve tension and migraine headaches.  However, be wary of self-medicating your pounding noggin with newly-concocted intravenous triple-shot espressos; studies have also linked caffeine intake with "rebound" headaches.  These headaches are produced when you lay off the good stuff only after your brain adapts to the effects of caffeine.
Diseases of the Brain -- Drinking a few cups of coffee a day may have surprising (but moderate) protective properties against debilitating and progressive neurologic conditions such as Parkinson's disease and Alzheimer's disease. 
Although this is just the tip of the iceberg when it comes to the studied benefits of coffee, it goes to show that ordering your daily cappa-mocha-latte may do more for you than just complement your oversized wayfarer shades and meticulously-cuffed skinny jeans. (I oddly envision the majority of my readers in this get up.)
Whether you identify as the extremely well-read neo-hipster described above or not, beware of placing coffee on a potable pedestal just yet.
Why You Should Stick To Decaf
Caffeinated beverages are not for everyone. Here's why:
Psychiatric Conditions -- Individuals sensitive to caffeine may experience a variety of psychiatric side effects when drinking even a small quantity of coffee. Anxiety, irritability, insomnia, and even panic attacks are associated with coffee intake. These symptoms may be due to an exacerbation of a concomitant psychiatric condition or may be due to a deficiency in adequately breaking down the drug to its non-effective form in your liver.  Regardless of the etiology, if you are considered to have Woody Allen-esque qualities or are just straight up unstable, you should probably hold the caffeine.
Heart Conditions -- For those coffee-naïve readers, beware of chasing the caffeine dragon if you suffer from hypertension (high blood pressure). Periodic coffee consumption has been shown to transiently increase blood pressure, which theoretically can put patients at an increased risk of cardiovascular events (stroke, heart attack). 
Dependence -- Remember that McDonald's commercial about the guy who wouldn't talk to anyone without his coffee? (Check it out here for a refresher.) Two lessons to learn: 1) No one likes people like that. Fact. And 2) If you reach that level of caffeine dependence, you have reached the end of your coffee career. Like many controlled substances, one should self-monitor caffeine intake, as caffeine may lead to abuse, tolerance, and dependence. 
Coffee is amazing. But like any drug, its caffeine content may carry side effects that outweigh the benefits of consumption. Be smart and take time to understand the health consequences of caffeinated beverages and come to your own conclusions.
In the meantime, I'll continue to tremulously troll the Web, awaiting the pending coffee crash that I alone will have to endure.
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