Child Psychology. Jean-Pascal Assailly

or after birth, or during the adolescence of the subject.

      The following are some recent examples; their contributions will then be presented through the course of the book in relation to the various fields of development.

      1.2.1.1. Studies with a prenatal onset: the EDEN study (study of pre- and postnatal determinants of child development and health)

      This study (Heude and Forhan 2015) aimed to investigate prenatal and postnatal determinants of child health and development in a French population. Pregnant women at <24 weeks of amenorrhea were recruited to the Poitiers and Nancy university hospitals between 2003 and 2006. Exclusion criteria were: being under 18 years of age, no informed consent, functional illiteracy in French, history of diabetes, plan to change address or no social security coverage.

      Of the 3,758 women invited to participate, 2,002 (53%) agreed to enroll in the study. Women with multiple pregnancies were also excluded. With deaths, the number fell to 1,899 infants enrolled at birth. Written informed consent was obtained twice from parents: at enrollment and after the child’s birth.

All variables included in the analysis were collected by means of paper self-completed questionnaires, with the exception of anthropometric measurements, which were assessed by clinical examination, and birth term, which was removed from medical records. The children were then followed up at 4, 8, 12 and 24 months and at five or six years.

      1.2.1.2. Studies from birth

      1.2.1.2.1. The ELFE Study (French longitudinal study since childhood)

      The ELFE (Étude Longitudinale Française depuis l’Enfance) Study is a nationally representative, multidisciplinary birth cohort of infants born to 18,040 women in 349 maternity hospitals in France in 2011. The protocol, design and recruitment procedures of the ELFE survey have been previously described (Vandentorren and Pirus 2006). Participating mothers and infants were recruited while in the maternity units and subsequently monitored. Exclusion criteria were: stillbirth, birth before 33 weeks gestation, multiple births and plans to leave metropolitan France within three years. Mothers had to be able to give informed consent in one of the study languages (French, English, Arabic and Turkish).

      Maternity data was collected using standardized interviews by trained interviewers and self-completed questionnaires. Information on obstetric characteristics was collected from maternal recalls and medical records. Two months after delivery, data was collected via telephone interviews.

      Information is collected annually and then every two years up to the age of 20, in the form of questionnaires (at home or by telephone), biological samples (at birth, three and six years), environmental measurements and follow-up logbooks (standardized collections of anthropometric measurements, etc.). The medical data is relayed by the parents from health records and completed by a medical examination at two years and a health check-up at six years.

      1.2.1.2.2. The EPIPAGE 2 Study (epidemiological study on low-gestational-age infants)

      The EPIPAGE (Étude épidémiologique sur les petits âges gestationnels) 2 Study is a national study to better understand the development of premature infants. The study focuses on infants divided into three groups: extremely premature (born before the end of the sixth month of pregnancy), very premature (born before the end of the seventh month of pregnancy) and moderately premature (born at the beginning of the eighth month of pregnancy). These children are followed from birth to age 12.

      1.2.1.2.3. The 1958 British National Child Development Study

The 1958 British birth cohort study was based on a sample of 18,558 British subjects, all infants born within one week in March 1958 (n = 17,638) and immigrants recruited at ages 7, 11 and 16 (n = 920). Information was collected from parents, teachers and physicians during childhood (birth, 7, 11 and 16 years) and from cosigners during adulthood (23, 33, 42, 45 and 50 years).

      1.2.1.2.4. The “Lifeways Cross-Generation Cohort” Study in the Republic of Ireland

      Participants were 943 mothers and their offspring, 890 fathers, 938 maternal grandmothers, 700 maternal grandfathers, 537 paternal grandmothers and 553 paternal grandfathers. Infant birth weights were standardized based on gestational age (1990 UK population) and then categorized as low, high or normal birth weights.

      Four birth periods were considered: the country’s independence (1916–1938); the Emergency Powers Act (1939–1946); the postwar baby boom (1947–1964) and modern Ireland (1964 onward). This is a three-generation cohort study established a priori to examine intergenerational influences on infants recruited during pregnancy in 2001–2003.

      1.2.1.3. Studies from childhood

      1.2.1.3.1. The Millennium Study

      The Millennium Study is a longitudinal study of a cohort of 18,818 children born in the United Kingdom between September 2000 and January 2002 (Connelly and Platt 2014). It is a multidisciplinary investigation designed to capture the effects of social, economic and health advantages and disadvantages on child development and other outcomes. There have been six surveys to date. The first was collected at about nine months of age, followed by surveys at ages 3, 5, 7, 11 and 14. At the end of the fifth survey, 13,287 children remained in the study.

      1.2.1.3.2. The CABLE (Childhood and Adolescent Behaviors in Long-term Evolution) Study

      The CABLE Study is a lifestyle research study in which 18 elementary schools were randomly selected in Taipei and Hsinchu, Taiwan. Data on gender, parent–child relationships and internalized symptoms from four waves of follow-up were analyzed: 2003 (9 year-olds), 2006 (12 year-olds), 2009 (15 year-olds) and 2012 (18 year-olds). A latent growth model was used to examine the impact of parent–child relationships and gender on the trajectory of children’s internalized symptoms.

      1.2.1.3.3. The Bergen Study

The first wave of the longitudinal Bergen Child Study (BCS) assessed a wide range of mental health problems in a total population of Norwegian schoolchildren aged seven to nine years (n = 9,430), using teacher and parent questionnaires in all schools, including special and private schools. Teacher questionnaires (n = 9,152) covered 97% of the population, whereas parent questionnaires (n = 6,295) covered 67% of the population.

      1.2.1.4. Studies from adolescence: the ABCD (Adolescent Brain Cognitive Development) Study

      The Adolescent Brain Cognitive Development (ABCD) Study is the largest long-term study of this type, relating to the relationship between cognitive development and subject health in the United States. It was launched in 2015, just before participants’ adolescence (11,878 subjects aged 9–10 years), at 21 research sites across the country to augment data collection such as neuropsychological assessments, biopsies and structural and functional neuroimaging data. The follow-up is planned to last 10 years. In addition to obtaining a nationally representative sample on adolescent brain development, other themes have been added to the survey: gender influences and, cardiovascular and hematological health.

      To conclude this brief methodological presentation, there have, of course, been other longitudinal studies around the world, but the sample presented above is representative of the main types.

      1.2.2. The issue of experimental mortality and retention

      Continued participation is essential for the validity of longitudinal studies, such as ABCD, where families are asked to participate in the study throughout the 10-year period.

      This therefore means communicating with families every six months by phone and annually in person, and more closely with youth in person as they transition into adolescence.

      Moreover, while