As we see from the original journal abstract following the article below, the study was more sophisticated than most in that there was some attempt to take social class into account. Maternal education is controlled for. It is however primarily paternal education that influences social class and there are other factors as well. So we have not escaped the influence of the fact that working class people eat more junk food and have poorer health generally. What they found could therefore have been a class effect, not a food effect.
I also suspect the factor-analytic approach used. I know factor analysis well, which is why I rarely use it. Factor identities are usually far from clear and relationships with them can be substantially altered by removing just one or two items from them. Conclusions derived from them are usually therefore pretty arbitrary. That one of the factors is identified as Western, whereas all or most of the participants were presumably Western, tends to raise the eyebrows a bit. Such a general appellation suggests that the factor was highly heterogeneous in its loadings, thus making generalizations about it very shaky. Looking at the individual foods and their relationships with behaviour would be much less inferential -- though appropriate error-rate adjustments would have to be made, of course (Let me hazard a guess that an experiment-wise error rate approach would have shown no statistically significant relationship between any food and any measure of mental health!). Identifying fruit and vegetables as the critical element in a factor that apparently comprised around 100 different foods is certainly an act of faith rather than a committment to rigorous hypothesis testing
A NEW study in WA has shown a link between Western-style diets and more mental health problems in teenagers. The research paper, from WA's Telethon Institute for Child Health Research, has just been published online in the respected international journal Preventive Medicine. Report author and leader of Nutrition studies at the Institute, Dr Wendy Oddy, said the results were based on detailed analysis of diet records and behaviour checklists that were collected from more than 1600 West Australian 14-year-olds in the Raine Cohort Study.
“Our analysis found that higher levels of behaviour and emotional problems were associated with a more Western-style way of eating, namely a diet high in takeaway foods, red meat, confectionary, soft drinks, white bread and unrefined cereals,” Dr Oddy said. “We also showed that these problems were less among teens with a more healthier style of eating, specifically those who ate more fruit and vegetables. “This suggests that if we want to reduce the high rates of mental health problems among young people, then improving their overall diet could be a good place to start.”
The study participants' food intake was assessed using a 212-item food frequency questionnaire. The Child Behaviour Checklist was used to assess internalising mental health problems, such as withdrawn and depressed behaviours, and externalising mental health problems, such as delinquent and aggressive behaviours.
Dr Oddy said previous studies have shown that one in five children are expected to develop some form of mental health problem by the time they reach adulthood, and that 50% of all adult mental health problems develop during adolescence. “We know that since 1985, children and teenagers have been increasing their energy intake by consuming more soft drinks and processed foods.
The number of overweight adolescents has doubled and obesity has tripled in that age group. At the same time there have been marked increases in sedentary behaviours such as TV viewing and computer use,” Dr Oddy said. “Investigating factors that influence mental health in young people must be a high priority. These findings show that there is a need to look at the overall diet, rather than concentrate on individual nutrients.”
The association between dietary patterns and mental health in early adolescence
By Wendy H. Oddya et al.
Objective: To investigate associations between dietary patterns and mental health in early adolescence.
Method: The Western Australian Pregnancy Cohort (Raine) Study is a prospective study of 2,900 pregnancies recruited from 1989-1992. At 14 years of age (2003-2006; n=1,324), the Child Behaviour Checklist (CBCL) was used to assess behaviour (characterising mental health status), with higher scores representing poorer behaviour. Two dietary patterns (Western and Healthy) were identified using factor analysis and food group intakes estimated by a 212-item food frequency questionnaire. Relationships between dietary patterns, food group intakes and behaviour were examined using general linear modelling following adjustment for potential confounding factors at age 14: total energy intake, body mass index, physical activity, screen use, family structure, income and functioning, gender and maternal education at pregnancy.
Results: Higher total (b=2.20, 95%CI=1.06, 3.35), internalizing (withdrawn/depressed) (b=1.25, 95%CI=0.15, 2.35) and externalizing (delinquent/aggressive) (b=2.60, 95%CI=1.51, 3.68) CBCL scores were significantly associated with the Western dietary pattern, with increased intakes of takeaway foods, confectionary and red meat. Improved behavioural scores were significantly associated with higher intakes of leafy green vegetables and fresh fruit (components of the Healthy pattern).
Conclusion: These findings implicate a Western dietary pattern in poorer behavioural outcomes for adolescents. Better behavioural outcomes were associated with a higher intake of fresh fruit and leafy green vegetables.
Preventive Medicine, Article in Press
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