This is completely wrong with someone saying that blood transfusion, mother-to-child and sexual contact are the main causes of hepatitis B. There are many ways to cause a result, but there is only one reason. There is only one cause of hepatitis B. Similarly, the only source of nightmares is the heartbeat!
Stress, disease, drugs and alcoholism do not exist. People still have nightmares as long as they have palpitations during sleep. On the other hand, even if stress, some drugs and drinking exist, people will not have nightmares as long as they have no palpitations during sleep. Stress, illness, drugs and drinking are all easy to cause nightmares, because these factors are easy to cause palpitations. Any factor that is easy to cause palpitations is easy to cause nightmares, and anyone who is easy to cause palpitations is easy to have nightmares. For example, women are more prone to palpitations than men, so women are more likely to have nightmares than men. Pregnant women are prone to palpitations, so pregnant women are prone to nightmares.