Birth Order, Personality, and Mental Health

Jessica Chang, MHC-LP.

If you have siblings or do not have siblings you have probably heard a cliche about your personality based on your birth order… and maybe you felt it was totally off base, but maybe you felt it was spot on. One’s birth order within their family has an impactful role in how one’s family sees them and how one sees themself, influencing one’s experiences, outlook, and mental health. So where did these cliches come from and do they have any scientific substance to them?

Birth Order Theory

Austrian psychotherapist Alfred Adler developed birth order theory in the 20th century, over 100 years ago. In this theory, Adler suggests that the order in which children are born (as well as family, community, and social aspects) affects their development and personalities, extending to career and educational success. Whether someone is the firstborn, middle child, youngest, or only child influences how their family sees and treats them, the amount of attention they receive, and the way they may compete for their parents’ attention - thus impacting one’s personality. Specifically, one’s perceived position within their family, i.e. psychological birth order, is more pivotal than their numerical birth order, which can at times differ due to various circumstances. In short, according to birth order theory, one’s birth order and the number of siblings one has significantly impacts their personality and potential.

What Adler Said about Oldest, Middle, Youngest, and Only children

Oldest Children

Adlerian theory mentions that firstborn children tend to be authoritarian and feel entitled to power. Studies show that oldest children tend to exhibit leadership skills.

Firstborn children may receive the most undivided attention from their parents for a period of time. As the parents’ first child, they tend to be extra attentive and careful in regards to all aspects of raising their child. They may appear most strict towards their oldest child and impart their beliefs and rules predominantly onto this child. Once the next child is born, attention is taken away from the oldest child. There may be expectations for the oldest child to set an example for younger siblings and demonstrate responsibility. Sometimes they may imitate the behavior of their parents in looking after younger siblings. Further, they may take on a leadership and teaching role and reinforce their own learning, leading to an increase in their intellectual abilities.

Oldest child traits may include:

• Self-reliant

• Serious attitude

• Conventional behavior, abide by rules (to keep the attention of their parents)

• High achiever

• Responsible

• Perfectionist

• Confident in their capabilities

• Uphold family traditions and morals

Middle Children

Birth order theory suggests that first- and last- born children have a unique position in the family, while middle children do not. Research shows that middle-born children may believe they have less emotional and financial support from their parents than their siblings do and may be more sensitive to rejection.

Middle children often feel squished between their older and younger siblings, robbed of any significant position within the family and overshadowed by their eldest sibling. They may have lower self-esteem or greater insecurity than their siblings due to their positionality within the family and act rebelliously, seeking attention. They may be super competitive, constantly aiming to be better than their older sibling in sports, cultural knowledge and language, school, etc. Middle children may focus more on building strong relationships outside of their family in interpersonal or romantic relationships and relate to people of different ages with ease.

Alternatively, middle children may create a niche role for themself in the family dynamic as “peacekeeper”. They may enjoy negotiation and compromise and appear even-tempered, exhibiting an ability to keep peace between family members.

Middle child traits may include:

• The most independent of the siblings

• Competitive

• Rebellious

• Ambitious

• Adaptable

• Thoughtful

• Sociable, outgoing

• Jealous, insecure

• Peacekeeper

• People pleaser

Youngest Children

Adler mentions youngest children tend to take 1 of 2 paths when developing their personality:

1. Try to excel in every way, often becoming the go-to person in the family… a clear journey to success.

2. Become avoidant… lacking in confidence or drive to excel.

Youngest children are the babies of the family, and this position is never taken away from them. The assurance of their place in the family can lead to them being spoiled, creative, rebellious, and outgoing. They may look for ways to differentiate themselves from their older siblings, thus developing an outgoing personality, humor, and social intelligence to elevate themselves in the family dynamic. They may try to gain attention in different ways than their sibling(s), asserting their uniqueness by becoming sociable, extroverted, and fun-loving.

Youngest children tend to have more freedoms than their siblings, receiving more hands-off parenting and relaxed rules. As the perpetual baby of the family, this can lead to the youngest child wanting to become “bigger” and making large plans for their lives that do not pan out. They may feel less capable or at a disadvantage in comparison to their older sibling(s) and constantly feel they have to catch up or compete with them.

Youngest child traits may include:

• Fun-loving

• Attention-seeking

• Outgoing, risk-taking

• Free-spirited

• Self-centered

• Selfless

• Creative

• Sociable, extroverted

• Immature

• Manipulative

• Dependent

Only Children

Only children are often “miracle babies”. Research suggests that only children may be high achievers, complete more years of education, and have secure, higher-status jobs.

Without siblings, only children are surrounded by adults since birth and socialized at home with parents and other adults. While they experience social settings with other children in school, their home life growing up often includes mimicking the behaviors of adults around them and becoming “small people” or “little adults”.

Similar to youngest children in this way, only children may receive more attention from their parents, plus they will not experience conflict or competition with siblings, which may lead to them being spoiled. Parents may be overprotective of their only child, leading the child to become dependent on their parents’ support. Only children may feel greater expectations from their parents and greater responsibility and may feel more intertwined with their parents’ lives. Not having to share their clothes, space, or attention from parents with siblings, only children may be intelligent and creative, but also stubborn and set in their ways.

Only child traits may include:

• Mature

• Imaginative

• Sensitive

• Intelligent

• Stubborn

• Self-reliant, easier transition into adulthood

• Perfectionist

• Diligent

• Leaders

• Conscientious

Other Factors (that may influence birth order personality)

1. Parental attitudes, background, and culture

2. Sibling age gaps and gender

3. Genetics and environment (socioeconomic status of parents, parenting styles or practices, peer and romantic relationships, work experiences, adoption or death of a sibling, etc.)

4. Confidence (how a child perceives themself)

Birth Order, Personality, and Mental Health

Alfred Adler’s birth order theory aims to explain the development and distinguishing of personality, and not necessarily mental health issues. Overall, research varies and there is little scientific evidence to suggest significant findings linking birth order and personality or birth order and mental health. There is most likely not a direct link between birth order and mental health issues, as mental health conditions are largely impacted by a combination of environmental, biological, and genetic factors. While one may associate their birth order with adverse or traumatic experiences, there is likely more to explore within the realm of one’s trauma. Although there is limited evidence supporting Adler’s birth order theory to this day, it can still be useful in providing a foundation in conceptualizing one’s position within their family and providing context towards how one navigates and operates in various environments. 

Sources

1.     Cherry, K. (2024). How Does Birth Order Shape Your Personality? Verywell Mind.

2.     Des Marais, S. (2022). Birth Order Theory: How Birth Order Affects Your Personality. PsychCentral.

3.     Sissons, B. (2024). What is birth order theory? MedicalNewsToday.

4.     What to Know About Birth Order (2023) | WebMD.