Caffeine has the ability to block the brain-signaling molecule adenosine.

This causes a relative increase in other signaling molecules, such as dopamine and norepinephrine 

This change in brain messaging is thought to benefit your mood and brain function.

One review reports that after participants ingested 37.5–450 mg of caffeine, they had improved alertness, short-term recall, and reaction time 

In addition, a study linked drinking 2–3 cups of caffeinated coffee (providing about 200–300 mg caffeine) per day to a 45% lower risk of suicide 

Another study reported a 13% lower risk of depression in caffeine consumers 

When it comes to mood, more caffeine isn’t necessarily better.

A study found that a second cup of coffee produced no further benefits unless it was consumed at least 8 hours after the first cup

Drinking between 3–5 cups of coffee per day or more than 3 cups of tea per day may also reduce the risk of brain diseases such as Alzheimer’s and Parkinson’s by 28–60% 

It’s important to note that coffee and tea contain other bioactive compounds (besides caffeine) that may also be beneficial.

SUMMARY

Caffeine may improve mood, decrease the likelihood of depression, stimulate brain function, and protect against Alzheimer’s and Parkinson’s disease.