Almost 80 to 90% of adults and children in North America consume caffeine in the form of chocolate, medications, alcohol, tea, carbonated drinks and perhaps most popularly, coffee, as per estimates. Last year, the National Coffee Association published a report indicating a sharp rise in the number of Americans who drink coffee. While the beverage has a rather polarizing reputation in terms of its effect on health, the general consensus among experts appears to be that moderate caffeine consumption is good for you.

But what happens when you stop consuming coffee? The scenario isn't rare as some may be forced to do so due to pregnancy or surgery while others may voluntarily attempt a caffeine detox.

“Caffeine is a central nervous system stimulant,” says Dr. Nicole Robertson. “It causes us to be more alert, awake and increases concentration.”

A neurotransmitter called adenosine, an important part of the brain, accumulates over the day and gives signals to the body whenever it has to rest or sleep. Caffeine blocks adenosine receptor sites, causing the opposite effect with increased energy and brain activity.

After a period of time, if the caffeine supply suddenly disappears, the adenosine is finally able to engage without restrictions, bringing drowsiness and headaches to compensate. In 2009, researchers from the University of Vermont studied brain electrical activity and blood flow velocity in participants. Their findings showed that stopping caffeine consumption also increases cerebral blood flow, causing a pounding headache. 

Many will experience this and exhibit a variety of other symptoms when giving up their regular dose, including fatigue, loss of alertness, and lowered concentration ability. These signs will begin 12 to 24 hours after quitting and can last for days until the body has recovered balance.

Rather than going cold turkey, some may attempt to simply reduce their intake during the evenings. Studies have suggested that caffeine can have disruptive effects on sleep patterns when consumed up to six hours before bed, potentially leading to insomnia.

But coffee quitters who had a stronger dependency may even experience panic attacks, mood swings, anxiety or depression. This is because caffeine indirectly activates the pituitary gland and the adrenal gland, leading to the production of adrenalin. The highly stimulating fight-or-flight hormone is known to increase energy and alertness. The sudden absence of this activity during withdrawal is what leads to mood swings.

Scientists once conducted a study where they examined the effects of caffeine on the brains of mice. The results showed that the number of adenosine receptors eventually increased to fight against the caffeine. It was suggested that this may be the reason why longtime coffee drinkers develop a tolerance and also find it harder to quit.

These effects have been taken seriously in recent years as the Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association classifies caffeine intoxication and caffeine withdrawal as mental disorders.