Can your birth order position predict how likely you are to develop a psychological disorder and can it predict your diagnosis? Of course not. Psychological disorders arise as a result of a number of factors - our genetic make-up, the way we were cared for when young, who we grew up with, role models both negative and positive, and the way we learn to interpret what happens to us. None the less, in my clinics I've come to notice some fairly predictable associations with birth order position and psychological diagnosis.
The most common reasons why people are referred to a psychologist are to relieve anxiety and/or depression, and to sort out relationship difficulties. Although individuals in all birth order positions may suffer from these problems, the reasons why they do so tend to differ according to their birth position.
A first-born is the only child in a family who once enjoyed the exclusive attention of their carer(s), and has to learn to share it. As a result, they often continue to seek approval from authority figures and therefore push themselves hard to gain recognition. They're most at risk of burnout, and easily hurt by criticism.
Middle-borns are more likely to feel anxious and depressed because they often have difficulty making career decisions. They grow up working so hard to get on well with others that often they've not had a chance to develop a strong sense of self-direction.
Last-borns tend to suffer readily from low self-esteem. They grow up surrounded by older, often more capable, siblings so they often think of themselves as less competent than they actually are. They also tend to give up easily, because there were always others to sort things out for them.
Single children are used to an orderly adult household, so can be prone to anxiety when things get out of control and may also feel anxious in social settings.
In relationships, first-borns and single children tend to set high standards, for themselves and their partner. As a result, their partner may feel they're sometimes controlling. Middle-borns can feel overlooked and "unheard" in their relationship. Last-borns often display ambivalence in relationships: they want to be looked after, but dislike feeling restricted.
These are but general tendencies, and they're all learned behaviours. That means they can be changed if an individual is willing to put in the necessary effort.
Linda Blair is a clinical psychologist. Her book is The Key to Calm.