Finding the True Number of Females with Autistic Spectrum Disorder by Estimating the Biases in Initial Recognition and Clinical Diagnosis

Abstract

The proportion of females whose ASD diagnosis is missed is unknown. The ratio of males to females with ASD is generally quoted as 4:1, though it is believed that there are biases preventing females from being diagnosed and that the true ratio is lower. These biases have not been clearly identified or quantified. Starting with a clinical dataset of 1711 children <18 years old, four different methods were employed in an inductive study to identify and quantify the biases and calculate the proportion of females missed. A mathematical model was constructed to compare the findings with current published data. The true male-to-female ratio appears to be 3:4. Eighty percent of females remain undiagnosed at age 18, which has serious consequences for the mental health of young women.

Keywords: autistic spectrum disorder; biases; male-to-female ratio; young women.

Figure 1

Categorising the ASD Study Population.

Figure 2

Venn Diagram of Bayes’ Theorem.

Figure 3

Learning curve of ASD over time.

Figure 4

The effect of equal biases on the proportion of girls found.

Figure 5

The effect of the final biases on the proportion of girls found.