Conduct disorder, ADHD, and oppositional defiant disorder are considered separate diagnoses of chronic behavioural problems. But desipte their differences, these conditions develop from similar risk factors in children's early environments, a 2012 review argues.
Childhood disruptive disorders pose a significant emotional and financial burden to children and their families as well as services and society at large. While the nature of these conditions is distinctive, there is considerable overlap between them in the environments that may trigger these disorders in the early years of life.
A systematic review undertaken by a team of researchers from Glasgow in 2012 examined the common risk factors underlying these conditions. While there is a growing recognition that these disorders are determined by a confluence of genetic and environmental factors, their paper focused on what is known about environmental risk factors in the antenatal period and up to four years of age.
After reviewing 47 papers that met their standards for quality of study design, the authors concluded that there are a significant number of common early life risk factors, but that some of these factors have been given undue prominence in research.
The risk factors break down into prenatal, perinatal and infancy periods.
In the prenatal period, maternal smoking, alcohol use, illness and stress during pregnancy have all been implicated in later disruptive behaviour disorders in children.
The largest amount of evidence was for the role of maternal smoking as a risk for ADHD. There was less evidence for the role of maternal illness or stress during pregnancy, although the results from the few studies that examined this appeared strong.
In the newborn period, the greatest amount of evidence linked low birth weight to ADHD. Eleven studies, including three large population-based studies, found that low birth weight children were more likely to develop ADHD than their normal birth weight counterparts. Some studies found that the link remained even when sex, race, mother’s education and mother’s IQ were taken into account.
In addition, two studies suggested that delivery complications may increase the risk of behaviour disorders, but the authors characterize the evidence for this link as “relatively weak.”
In the early childhood period (up to four years), parental stress, early deprivation, and adoption or separation were each implicated as risks for disruptive behaviour. There was strong evidence that parental stress and children’s behaviour disorders go hand-in-hand. However, it was not always clear from these studies whether parents’ anxiety and depression led to their children’s problems, or vice versa.
Fewer studies examined the impact of early deprivation, adoption, and separation, but the evidence that these disruptions put a young child at higher risk of developing behavioural and other psychiatric disorders is of “high quality,” the authors found.
An important message from any systematic review is that the lack of evidence for a particular relationship may not be down to a weak link between a risk and an outcome, but rather because few studies have investigated the relationship.
The authors of this review make the point that although a wide array of factors have been implicated in disruptive behaviour disorders, the field has tended to focus on particular risks and certain diagnoses.
More specifically, the article suggests that there has been a disproportionate amount of research on the role of prenatal smoking by mothers “at the expense of research on early life adversity.” In addition, the majority of the research has concentrated on ADHD, with relatively fewer studies examining risk factors for oppositional defiant disorder (ODD) or conduct disorder.
Moving forward, large, prospective research designs are needed to allow us to pull apart the role that genetics, environment, and individual development play in children’s chronic behaviour problems.
Latimer, K., Wilson, P., Kemp, J., Thompson, L., Sim, F., Gillberg, C., Puckering, C. and Minnis, H. (2012). Disruptive behaviour disorders: A systematic review of environmental antenatal and early years risk factors. Child: Care, Health and Development. doi: 10.1111/j.1365-2214.2012.01366.xReturn to Features