Although middle child syndrome is a widespread and popular observation, psychologists say that it actually does not exist. Experts on child development  say that it is not an actual clinical disorder and that the syndrome can be seen in children born in any order in the family. Additionally, despite all the stereotypes designated to being a middle child, psychologists say that may actually have some social and psychological benefits.
Dr. Ray Guarendi, author of a book on parenting, describes the syndrome as marked by "feelings of isolation, of not belonging." He explains that kids in the middle neither enjoy parental attention given to the eldest, nor the lenient parental standards bestowed to the youngest. "The middle child is supposedly lost in the shuffle, caught in between with no unique position of his own," Guarendi continues.
He details other symptoms of the middle child syndrome such as "poor self-concept", responding to their perceived lack of parental attention by becoming shy and withdrawn, or by acting out and demonstrating behavioral problems. According to the News.Mic , other behavioral cues are low self-esteem, jealousy, feelings of emptiness or inadequacy and unfriendliness. However, Dr. Guarendi asserts that these behavior can also be experienced by other children in the family, not just the middle child.
Research indeed have suggested that being a middle child, and birth order in general, has very little effect on a person's personality. According to the Business Insider , being in the middle might also have some benefits such as the ability to negotiate including in career paths. A study illustrating how the middle child syndrome can be beneficial shows that middle children tend to have to negotiate what they want since they are sometimes pushed in the middle, developing their ability to rely on themselves which translates to success in personal and business life.