Brain alterations greater in specific phobia vs other anxiety disorders

Specific phobia is associated with brain alterations that surpass those of other anxiety disorders in terms of effect size and extent, reveals a study. Such changes are not limited to decreases in brain structure.

In addition, “phenomenological differences between phobia subgroups were reflected in diverging neural underpinnings, including brain areas related to fear processing and higher cognitive processes,” according to researchers.

In this study, the ENIGMA Anxiety Working Group assessed differences in brain structure between individuals with specific phobias and healthy control participants as well as between the animal and blood-injection-injury subtypes of specific phobia.

Researchers combined data sets from 31 studies to include a final sample with 1,452 participants with phobia and 2,991 healthy participants (aged 5‒90 years, 61.7 percent female). They carried out imaging processing and quality control using established ENIGMA protocols and examined subcortical volumes as well as cortical surface area and thickness in a preregistered analysis.

Individuals with phobia had mostly smaller subcortical volumes, mixed surface differences, and larger cortical thickness across different regions when compared with the healthy participants. Additionally, the phobia subgroups demonstrated differences, such as a larger medial orbitofrontal cortex thickness in blood-injection-injury phobia (n=182) relative to animal phobia (n=739).

Of note, these findings were driven by adult participants and no significant results were seen in children and adolescents.

“The findings implicate brain structure alterations in specific phobia, although subcortical alterations in particular may also relate to broader internalizing psychopathology,” the researchers said.