There are numerous triggers that could cause fainting. Essentially they all lead back to a drop in blood pressure or not being able to get enough oxygen. Often, too, fainting is a precursor to something more serious so it should never be dismissed as trivial simply because you have recovered in 5 seconds. The danger of fainting, of course, is that you could sustain a real trauma in the process, such as a concussion, or even injure others, for example if you are driving at the time.
The medical term for fainting is vasovagal syncope. It is, therefore, to do with both the heart (vaso) and the nervous system and signals from the brain (vagus – the largest cranial nerve). When you faint, your body essentially short circuits. Usually, it does so not because it is forced to, but as a pre-emptive measure to protect you from something worse happening. Here are many of the varied reasons you could pass out, and some are less obvious than you would have imagined.
Anything that can induce an irregular heartbeat, whether fast or slow, will change blood pressure. A sudden change in blood pressure will mean that the brain does not get enough blood to process and send signals such as ‘stay awake’ to the body. When blood flow to the brain is short-circuited, whether the pressure is high or low, you can lose consciousness for a short while and faint. One of the reasons behind this is stress.
Emotional stress or volatility can not only raise blood pressure, but also increase cortisol levels. Research proves it can stimulate the sympathetic nervous system and cause an irregular heartbeat. Statistics indicate that 20 percent to 40 percent of unexpected cardiac deaths are brought on by emotional stressors. In other words, it leads to cardiac abnormality that’s triggered by emotional stress and increases the risk of arrhythmias. Other than death, it can also lead to fainting. Common examples are when people received unexpected bad news about a loved one.