Purpose

This study aimed to assess whether high-income countries have a lower mean age at the time of diagnosis of autism spectrum disorder (ASD) than low- and middle-income countries.

Method

We reviewed studies related to ASD diagnoses and the time of first concerns in low-, middle-, and high-income countries, published in PubMed, SciELO, Lilacs, and ScienceDirect. Thirty articles were included: 13 from low- and middle-income countries and 17 from high-income countries.

Results

The average delay between initial concerns and diagnosis was 32.33 months, with initial concerns averaging 23.64 months and diagnosis at 55.97 months. No statistical differences were found between countries with low-, middle-, and high-income.

Conclusions

This review found a considerable delay in ASD diagnosis despite an early presence of recognized signs and symptoms. It highlights the urgent need for standardized tools for early ASD diagnosis.