A new research from neuroscientists and molecular biologists at University of Southern California has shown that a missing brain protein may be the culprit in cases of severe over-worry, where the fear perseveres even when there`s nothing of which to be afraid.

The researchers examined mice without the enzymes monoamine oxidase A and B (MAO A/B), which sit next to each other in our genetic code as well as on that of mice.

Prior research has found an association between deficiencies of these enzymes in humans and developmental disabilities along the autism spectrum such as clinical perseverance - the inability to change or modulate actions along with social context.

"These mice may serve as an interesting model to develop interventions to these neuropsychiatric disorders," senior author Jean C. Shih, USC Professor and Boyd and Elsie Welin Professor of Pharmacology and Pharmaceutical Sciences at the USC School of Pharmacy and the Keck School of Medicine of USC, said.

"The severity of the changes in the MAO A/B knockout mice compared to MAO A knockout mice supports the idea that the severity of autistic-like features may be correlated to the amounts of monoamine levels, particularly at early developmental stages," Shih said.

The study is published in the Proceedings of the National Academy of Sciences.