The term middle child syndrome has its origins in 1912 and was coined by the doctor and psychotherapist Alfred Adler. According to Adler's theory, the most outstanding personality traits of middle children would be rebellion, anger and jealousy.

A 1998 report concluded that middle children may even have more distant relationships with their loved ones, especially with mothers. The expert emphasizes that to avoid differences between siblings, it would be best to establish adequate, equitable emotional education with all children, Sheila García says.