Aim The functional polymorphism Val158Met in the catechol-O-methyltransferase (COMT) gene was analysed to determine its association with maternal stress and childhood total difficulties.
Method Data were collected at birth from a group of infants who were born small for gestational age and a group who were born at an appropriate size for gestational age and had been enrolled in the Auckland Birthweight Collaborative Study. Children were followed up at the ages of 1 year, 3 years 6 months, 7 years, and 11 years. At the age of 11 years, DNA samples were collected from 546 children (270 females, 276 males): 227 children born small for gestational age and 319 children born at an appropriate size for gestational age. The main independent variable was perceived maternal stress at birth and at 7 and 11 years of age, assessed using the total difficulties scale of the Strength and Difficulties Questionnaire. IQ was assessed at the age of 7 years.
Results Met/Met homozygotes were at a significantly increased risk of behavioural and emotional problems at the ages of 7 (p=0.002) and 11 years (p=0.003), relative to either heterozygous or homozygous carriers of the Val158Met polymorphism, but only when they were exposed to maternal stress in utero. Met/Met homozygotes had, on average, IQ scores that were four points higher than those of Val/Val homozygotes (p=0.010).
Interpretation These findings emphasize the potential long-term consequences of prenatal stress for genetically susceptible individuals during neurodevelopment in utero. Our findings add to the general understanding of the aetiology and developmental nature of childhood emotional and behavioural problems.