Thanks again to Dr. Hale for pointing out a new study on diet and ADHD. And thanks again to Australia for studying diet and psychiatric issues observationally, though a prospective controlled dietary trial (from any country) would be nice every now and then. Throw us psychiatrists a bone. I know we aren't cardiologists and don't make the big $$ with procedures, but we're important too. Ahem.
The design of this study is rather interesting. In 1991, researchers recruited a bunch of pregnant women in and around Perth, Australia, to allow their children to be followed for medical science. 2900 or so agreed, and the moms/families answered questionnaires at 18 weeks pregnant, 34 weeks pregnant, birth, 1, 2, 3, 5, 8, 10, and 14 years of age. By the 14 year mark, 1,860 of the original cohort of 2868 live births sent in their SASE with answers about diet, sociodemographic, and lifestyle factors. Each caregiver was asked if their child was diagnosed by a health professional with ADHD, and trained research assistants followed up with the healthcare professional to confirm the diagnosis, including the ADHD subtype (inattentive, hyperactive, or combined). In the end, the diagnosis or lack thereof was confirmed for 1634 adolescents.
Diet was evaluated via a food frequency questionnaire - which is always a bit of a shot in the dark, but the questionnaire was confirmed both by the kid's primary caregiver and by a visit with a research assistant. The researchers divided the diets into two patterns - "Western" and "Healthy." A "Western" diet had higher total fat, saturated fat, refined sugars, and sodium with lesser amounts of omega 3, fiber, and folate. (Alas - poor sat fat is lumped in with refined sugars and processed food (sodium) YET AGAIN). The "Healthy" pattern had high omega 3, fiber, and folate and low saturated fat, refined sugars, sodium, and total fat.
Tons of numbers were crunched. Maternal smoking, poverty, alcohol, stressful events during pregnancy and early childhood, physical activity... many, many, many numbers were crunched. In the end, 10% of the boys and 3% of the girls had a diagnosis of ADHD. Adolescents with a "Western" dietary pattern were a little more than twice as likely to have ADHD than those with a "Healthy" pattern. Three or more "stressful events" during pregnancy were also associated with ADHD in boys, but not in girls. Kids who exercised outside school hours were less likely to have ADHD.
Specific food groups with increased risk for ADHD included fast food, processed meats, red meat, high fat dairy products (ice cream?), soft drinks, and crisps (chips, I think they mean!!).
Now some discussion.
First, Evolutionary Psychiatry would like to point out that this is an observational study, with all the limitations therein. Good for speculation, but not good for recommendations. Fortunately, we at Evolutionary Psychiatry love to speculate.
Let's review some other data about ADHD and nutrition. Lower plasma omega 3 and higher omega 6 has been observed in kids with ADHD (1). ADHD is also linked in a prospective, randomized controlled trial with food additives and food colorings, which would be higher in a "Western" diet. A lack of micronutrients (such as zinc) has also been associated with ADHD (and supplementation was found to be helpful in an intervention trial) (2)(3). All these issues would be associated with a Western (but not a paleolithic-style) dietary pattern.
One more important thing to consider. ADHD is highly genetic (perhaps related to inherited inefficiency with dopamine receptors in the frontal lobes). I'm an adult psychiatrist - often I will get an adult coming in saying, "My son was just diagnosed with ADHD, and you know, I think I've had it my whole life too." Eating "healthy" requires some planning and organization (though it is not that difficult once you get used to the dos and don'ts). When ADHD affects whole families, fast food can be an easier solution than cooking and preparing meals at home.