Figure A-29. Primary Research Publication Output and Trends in Subcategories of Autism Risk Factor Research. 

Pie graph and line graph.  Both the pie graph and line graph plot three subcategories of autism risk factor research: genetic risk factors, environmental risk factors, and epigenetics.  The pie graph shows the number of primary research articles related to autism risk factor research in the year 2010 as a total and proportion of each of the 3 subcategories.  The largest segment of the pie graph is genetic risk factor publications, which accounted for 60% of primary autism risk factor publications in 2010, totaling 169 publications.  The second largest segment is environmental risk factor publications, with 36% of 2010 primary research risk factor publications, totaling 103. The third and smallest segment is epigenetics, which accounted for 4% of risk factor publications with a total of 12.  

The line graph plots the total number of primary research publications for the 3 subcategories across the years 1980 to 2010.  The y-axis is labeled number of publications related to ASD risk factors, and the x-axis displays the year.  In 1980, all 3 subcategories had 6 or less publications a piece. The annual rate of publication in the subcategories of genetic risk factors and environmental risk factors began to grow more quickly around the year 1999 and in the year 2010 there were 169 genetic risk factor primary research publications and 103 environmental risk factor primary research publications.  The number of publications related to the third subcategory of epigenetics remained near zero until the year 2008, when it started increasing. In 2010, there were 12 ASD risk factor publications related to epigenetics.