Nightmares have been the subject of research for centuries: some have given them a mystical meaning, taking them as a warning of trouble, while others have explained everything with psychoanalysis. There can be many reasons for nightmares: from ordinary stress at work to long-term mental disorders.

Scientists shared their scientific thoughts on why we have nightmares. The details were provided by I News.

Nightmares can be realistic and surreal, in both cases they make you wake up in a cold sweat and with a sense of fear.

Scientists from Harvard Medical School reassure with a simple definition: "nightmares are just dreams that cause a strong but unpleasant emotional reaction".

Nightmares usually occur during REM sleep. It can be recognised by external signs:

• rapid eye movements;
• irregular heartbeat;
• rapid breathing.

Every night, a person has four to five short periods of REM sleep. Nightmares most often occur when REM intervals are lengthened.

The terrifying images created by the subconscious and imagination are usually very vivid and memorable during this period.

Researchers disagree about why we actually dream. Neurologist Sigmund Freud believed that dreams are a way to get rid of repressed thoughts and feelings. Some scientists believe that dreams are meaningless and that we shouldn't try to solve them.

Nightmares can be triggered by a variety of reasons:

• stress and anxiety;
• irregular sleep;
• reading a scary book or watching a horror film before going to bed;
• taking certain medications;
• mental disorders.

One of the causes of nightmares is post-traumatic stress disorder (PTSD). Nightmares are one of the criteria for diagnosing the disorder.

A study by the University of Pittsburgh School of Medicine showed that 80% of people with post-traumatic stress disorder often have nightmares.

Earlier, OBOZREVATEL reported that scientists have made an important discovery about daytime sleep - it can save you from diseases.

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