A long-term study following 1,000 families with children born using IVF between 1994 and 2002 in the UK and US has shown the importance of parenting in the outcome of a child's behaviour.
In the study, which investigated the mental well-being of both the parents and children, some of the children were biologically related to their parents, while others were unrelated and conceived using either donor sperm or eggs, or both. This gave the researchers a unique opportunity to compare the role of nature (genes) and nurture (the environment) in the development of a child's behaviour.
The researchers asked the mothers and fathers of the children to complete a questionnaire, which covered topics such as their mental well-being (depression, aggression), their parenting towards the child - positive (warmth) and negative (hostility), as well as their child's mental well-being. The researchers then compared the data from the different groups of related and unrelated parents.
Professor Gordon Harold, a psychologist who led the study said: 'Associations were found between parent and child symptoms of depression and aggression among parents and children who were genetically related, but, crucially, also among parents and children who were not genetically related'.
Until recently, Professor Harold was the head of The Centre for Research on Children and Families at Otago University in New Zealand. He told the New Zealand Herald: 'Interventions that target hostile behaviours from parents are likely to pay dividends in reducing behavioural problems in children'. But cautiously added: 'What this paper is not saying is that genetic factors do not matter in human development. Absolutely not!'
The work itself, however, was carried out by scientists at Cardiff University and University College London in the UK, and was funded by the Wellcome Trust. The findings were published in the journal Psychological Medicine.