Understanding the causes of stuttering may no longer be a mystery, as US researchers on Monday provided evidence to show that the speech disorder is influenced by our genes.

Stuttering -- characterised by syllable and word repetitions, sound prolongations, and breaks between words -- is the most common fluency disorder, with more than 400 million people affected worldwide. And yet, the causes of this common speech disorder are unclear.

In the paper, published in the journal Nature Genetics, the researchers identified 48 genes, and 57 distinct genomic loci associated with the speech disorder, based on genetic data of more than 1 million individuals.