Parental personality and early life ecology: a prospective cohort study from preconception to postpartum

Personality reliably predicts life outcomes ranging from social and material resources to mental health and interpersonal capacities. However, little is known about the potential intergenerational impact of parent personality prior to offspring conception on family resources and child development across the first thousand days of life. We analysed data from the Victorian Intergenerational Health Cohort Study (665 parents, 1030 infants; est. 1992), a two-generation study with prospective assessment of preconception background factors in parental adolescence, preconception personality traits in young adulthood (agreeableness, conscientiousness, emotional stability, extraversion, and openness), and multiple parental resources and infant characteristics in pregnancy and after the birth of their child. After adjusting for pre-exposure confounders, both maternal and paternal preconception personality traits were associated with numerous parental resources and attributes in pregnancy and postpartum, as well as with infant biobehavioural characteristics. Effect sizes ranged from small to moderate when considering parent personality traits as continuous exposures, and from small to large when considering personality traits as binary exposures. Young adult personality, well before offspring conception, is associated with the perinatal household social and financial context, parental mental health, parenting style and self-efficacy, and temperamental characteristics of offspring. These are pivotal aspects of early life development that ultimately predict a child’s long-term health and development.

(1 year postpartum) Household income Household income around immediately prior to conception and after birth were measured using the items "What was your gross household income (in AUD) (pre-tax: including pensions and allowances) that you received in the last financial year from all sources? (before becoming pregnant)?", and "What will be your gross household income (in AUD) (before tax) from all sources for the financial year following the birth of your baby?". Response options ranged from 0 (less than $10,000 p/a) to 18 (more than $200,000 p/a). Each item was converted to a continuous scale by taking the median value of the range provided in each response option. For the last option (more than $200,000 p/a), we replaced the value with $225000.

Stressful life events
Stressful life events were assessed using the List of Threatening Experiences (LTE) 1 . This scale contains 12 categories of events including illness, death, relationship difficulties, financial difficulties and encounters with crime of the respondent and those around them (e.g., "In the last 12 months, has someone in your family suffered a serious illness, injury or assault"). It has shown sound construct validity and temporal stability in large populationbased cohorts 2 . Participants who responded "yes" further reported how much distress that event caused them (responses ranging from 0 (none) to 3 (very much)), and how long the distress lasted in weeks. A total score was created by summing the number of life events where participants reported experiencing "quite a lot" or "very much" distress. Social support The Maternity Social Support Scale (MSSS) 3 used to assess how often the mother feels supported and loved by family, friends and her partner, and how often she has conflict with her partner (e.g., "I have good friends who support me"). This scale contains six items, with response options ranging from 1 (never) to 5 (always). Items 4 and 5 were reversed scored. Participants who were not in a relationship were not asked items pertaining to partner social support (items [3][4][5][6]. The scale has shown good reliability and predictive utility 3,4 . An overall mean score was derived by calculating the average of responses across items, where higher scores indicated greater social support.

Partner relationship quality
Partner relationship quality was assessed using seven items from the Dyadic Adjustment Scale (DAS) 5 , a measure of intimate relationship satisfaction (e.g., "Do you confide in your partner?") that assesses dyadic satisfaction, dyadic consensus, dyadic cohesion and affectional expression. Response options range from 0 (all the time) to 5 (never). Items 1 and 6 were reverse scored to indicate greater relationship satisfaction, and items were averaged to create an overall mean score.

Maternal depressive symptoms
Maternal depressive symptoms were assessed using the Edinburgh Postnatal Depression Scale (EPDS) 6 . The EPDS is a 10-item rating scale designed to screen for postpartum depressive symptoms and also validated for antenatal use 7 . Response options range from 0 to 3. Items 1, 2 and 4 were reverse scored such that higher scores indicate more depressive symptoms, and all items were summed to create an overall total score.  [10][11][12] . These scales have shown sound psychometric properties (including scale reliability and construct validity) in a large population of Australian parents 12 . These items ask the mother about her behaviour towards her child, with a focus on affection and bonding (e.g., "How often do you hug or hold your child for no particular reason?"). Response options range from 1 to 5. An overall score for each parenting behaviour was derived as an average of responses across items, such that higher scores reflect higher scores for the named behaviour.

Parent-infant bonding
The PBQ is designed to screen for parent-infant bonding problems as perceived by the mother and consists of 25 items representing four factors: 'general impaired bonding' (e.g. I feel happy when my baby smiles or laughs -reversed); 'rejection and anger' (e.g. I feel angry with my baby); 'infant-focused anxiety' (e.g. My baby makes me feel anxious); and, 'risk of abuse' (e.g. I feel like hurting my baby) 13 . Response options range from 0 (always) to 5 (never). The scale has demonstrated good reliability, specificity and predictive value for bonding problems diagnosed through expert consensus using interview and case record data 14,15 . Items were reverse scored such that higher scores indicate greater parental-infant bonding, and were averaged to create an overall mean score. At each wave, participants were asked the highest level of education each of their own parents had achieved (e.g., "What is your FATHER's highest level of education?"). Participants' parents' high school non-completion was defined as neither parent had completed high school.

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Participants' parents' separation/divorce At each wave, participants were asked to indicate whether their own parents were married, separated/divorced, had passed away or other, and the participant's age when this happened. A dichotomous variable was derived to indicate whether participants' parents had experienced a separation or divorce during adolescence.

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Participants' high school non-completion Participants were asked "What was the last year of secondary school you completed?". Response options were "Year 8", "Year 9", "Year 10", "Year 11"and "Year 12". Participants were also asked "What is your highest educational qualification?" in VAHCS wave 9. High school non-completion was defined as participants who had less than year 12 education.

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Participants' positive parental bond with own mother and father The 25-item Parental Bonding Instrument (PBI) 24 was administered in adolescence to assess the bond between adolescent participants and their own parents. The PBI consists of two scales: care and overprotection. Responses ranged from 0 (very unlike my parent) to 3 (very like my parent). Positive parental bond was defined as having both parents display high care and low overprotection 24 .

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Participants' life stressors Stress was measured using the stress subscale of the Stress and Social Support Inventory 23 . The scale included 6-items that assessed 6 different types of stressors: family, home, school, money, social life and relationships (e.g., "Do you have enough money to spend?"). Response options range from 1 (I'm happy) to 3 (It's giving me problems at the moment). Presence of life stressors was defined as experiencing 2 or more stressors that caused the participant problems at one or more adolescent waves.

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8 Construct Description VAHCS waves assessed Participants' binge drinking Alcohol use at each adolescent wave was assessed using a 7-day drinking diary which asked participants the number of standard drinks consumed per drinking day. Binge drinking was defined as ≥5 standard drinks per drinking day at one or more adolescent waves.

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Participants' daily smoking At each adolescent wave, participants were asked to report the number of cigarettes they smoked during the last week. Daily smoking was defined as smoking 6-7 days per week at one or more adolescent waves.

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Participants' mental health problems At each adolescent wave, adolescent mental health problems were measured using the Revised Clinical Interview Schedule (CIS-R) 25 , a structured psychiatric interview designed to assess symptoms of anxiety and depression in community samples. The CIS-R has been validated for use with adolescent populations 26 . At each wave, total score was dichotomised at ≥12 to identify mixed depression-anxiety symptoms at a level lower than major depressive or anxiety disorder, but which a general practitioner would view as clinically significant 25 . Presence of mental health problems was defined as a score of ≥12 at one or more adolescent waves.

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Participants' underweight Participants' overweight At every adolescent wave, adolescent height and weight were measured by two research assistants trained at baseline 27 . Participant weight was measured to the nearest .1 kg with participants in minimal school uniform, using portable digital scales. A weight of 1 kg was deducted from the measure to account for the weight of the residual clothing. Height was measured with shoes removed using a rigid stadiometer and recorded to the nearest centimetre. Self-reported weights and heights were used for those who had left school in the later teenage waves. Underweight was defined as BMI <18.5 at one or more adolescent waves, and overweight was defined as BMI ≥25 at one or more adolescent waves 28 .

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Psychol. 15, 195-203 (1981 Supplementary Table 6a. Sensitivity analyses for associations between parent agreeableness and perinatal outcomes. b = standardised regression coefficient. Complete case models included participants with available data on all analysis variables, and were adjusted for all assessed family of origin, sociodemographic, mental health, and behavioural characteristics. Mutual exposure adjustment models were adjusted for all other personality traits. Binary exposure models included the personality trait exposure dichotomised at the 15 th %ile, with the risk category representing low levels of the named trait, and were unadjusted.   Supplementary Table 6b. Sensitivity analyses for associations between parent conscientiousness and perinatal outcomes. b = standardised regression coefficient. Complete case models included participants with available data on all analysis variables, and were adjusted for all assessed family of origin, sociodemographic, mental health, and behavioural characteristics. Mutual exposure adjustment models were adjusted for all other personality traits. Binary exposure models included the personality trait exposure dichotomised at the 15 th %ile, with the risk category representing low levels of the named trait, and were unadjusted.   Supplementary Table 6c. Sensitivity analyses for associations between parent emotional stability and perinatal outcomes. b = standardised regression coefficient. Complete case models included participants with available data on all analysis variables, and were adjusted for all assessed family of origin, sociodemographic, mental health, and behavioural characteristics. Mutual exposure adjustment models were adjusted for all other personality traits. Binary exposure models included the personality trait exposure dichotomised at the 15 th %ile, with the risk category representing low levels of the named trait, and were unadjusted.   Supplementary Table 6d. Sensitivity analyses for associations between parent extraversion and perinatal outcomes. b = standardised regression coefficient. Complete case models included participants with available data on all analysis variables, and were adjusted for all assessed family of origin, sociodemographic, mental health, and behavioural characteristics. Mutual exposure adjustment models were adjusted for all other personality traits. Binary exposure models included the personality trait exposure dichotomised at the 15 th %ile, with the risk category representing low levels of the named trait, and were unadjusted.   Supplementary Table 6e. Sensitivity analyses for associations between parent openness and perinatal outcomes. b = standardised regression coefficient. Complete case models included participants with available data on all analysis variables, and were adjusted for all assessed family of origin, sociodemographic, mental health, and behavioural characteristics. Mutual exposure adjustment models were adjusted for all other personality traits. Binary exposure models included the personality trait exposure dichotomised at the 15 th %ile, with the risk category representing low levels of the named trait, and were unadjusted.