Risk Factors For Attention Deficit/Hyperactivity Disorde

Environmental Health Sciences

Investigators

Linked publications & trials

Abstract

Aims: The primary aims of the project are 1) to describe the prevalence of ADHD and how it varies by age, race, gender, and SES, 2) to test the hypothesis that preterm and post-term births are at higher risk for ADHD and 3) to evaluate the role of maternal smoking, maternal occupation, maternal alcohol consumption and pregnancy complications as risk factors for ADHD. Procedures and techniques: The purpose of this project is to evaluate environmental, reproductive and familial risk factors for ADHD within a population-based cohort. We are in the process of screening all 8,000 elementary school students in the Johnston County School system for ADHD, first through teacher completed forms and later through parent interviews. We have developed a practical method to apply clinical case criteria for ADHD to an epidemiologic setting. This allows us to provide important information that has not previously been available on prevalence, risk factors, and treatment patterns of ADHD. Accomplishments: Because developing a case definition for ADHD in epidemiologic studies is challenging, we are writing a paper that explains the key decision points in creating a working case definition (see below), using data from the pilot study to illustrate the impact of these decisions. The key decision points include deciding how to combine reports from parents and teachers, how to evaluate subjects taking medication that suppress symptoms, how to measure impairment, how to adjust estimates for non-response if two-stage sampling is used, and how to use the age-of-onset criteria. There has been considerable interest in our screening approach from other investigators designing epidemiologic studies of ADHD; we have supplied detailed descriptions of our screening approach to groups planning studies in California, Wisconsin, Maryland, and Spain. In addition, I was invited to give keynote talks on our methodology at a conference on children's environmental health, and at a symposium on ADHD sponsored by the society of neurotoxicology. Data collection for the study has ended. We are in the last phase of entering, cleaning, and editing the data. We already have the entire teacher screening data available for analysis. The first major finding from our study is that ADHD is very common among children in the Johnston County elementary schools. Ten percent of all elementary school children had previously been diagnosed with ADHD by a psychologist or a physician. Seven percent of all elementary school children are currently receiving ADHD medication treatment. We also found that among children who had been diagnosed, African-American and Hispanic students were about half as likely to be taking medication to treat ADHD. We wanted to determine whether the high prevalence of medication treatment in Johnston County is atypical. The U.S. Drug Enforcement Administration collects mandatory reporting data on the distribution of stimulant medication to pharmacies, hospitals, and physicians throughout the U.S. Using these data, we mapped the rates of methylphenidate (Ritalin) distribution for all N.C. counties and calculated consumption rates accounting for the age structure of the counties. We found that Johnston County ranked 54th out of 100 North Carolina counties in their methylphenidate distribution rate for 1998. This suggests that the high ADHD medication treatment rates we observed in Johnston County elementary schools are not unusual and may be typical for many North Carolina counties. Using these data, we found the most important factors predicting methylphenidate distribution rates in North Carolina counties county were population density, number of primary care physicians and to a lesser extent, per capita income and proportion of non-white residents. Given the large numbers of children being treated with stimulant medication, there is surprisingly little data on either the long-term benefits or long-term risks of this treatment. We have written a chapter on the public health implications of the use of stimulant medication to treat ADHD for a book on evidence-based approaches to the diagnosis and treatment of ADHD.