The effects are quite complex and can be beneficial. In short, it's ok to drink it, but in moderation and not too late in the day if you wanna actually be able to sleep.
One thing this article doesn't explain, is that caffeine in very high concentrations is actually toxic, so don't go mad with it, or you could get more than a headache and the jitters.
www.theguardian.com
One thing this article doesn't explain, is that caffeine in very high concentrations is actually toxic, so don't go mad with it, or you could get more than a headache and the jitters.

The truth about caffeine: how coffee really affects our bodies
Every day, around the world, 2bn cups are consumed. But what actually happens after you swallow that first mouthful? Here is everything you need to know