Written by Mojo, reviewed by Medical Doctor Dr Matthew Chan

Here’s how erections work:

1. Your brain senses sex might be on the cards and starts firing brain signals to tell your body it’s game on 
2. These increase your heart rate and allow swift blood flow to your penis
3. More messages travel down your nerves to tell the muscle at the bottom of the penis to tighten and hold the blood in
4. Now you have an erection, sex can begin

Erectile dysfunction (ED) can occur when any of these stages get disrupted.

As these steps involve your brain, nerves, muscles, blood flow, hormones, mood (and more), you may have already guessed that ED has lots of causes. 

These broadly fall into two camps, physical and psychological - but they can also intermingle, so your erections can be negatively impacted by your body and your mind in different ways, all at the same time.