Scientists have studied brain structure for decades, so most disease-related structural anomalies have been long known. New findings of this nature are rare—yet last summer one neuroscientist studying depression published just that. Over nine years of sorting through countless brain images, Jerome J. Maller of Monash University and Alfred Hospital in Melbourne noticed a particular type of brain abnormality that seemed to show up more often in depressed patients. Their occipital lobes were often wrapped around each other.

Maller and his colleagues investigated further and found that depressed patients are indeed three times as likely to have wraparound lobes. Occipital bending occurred in 35.3 percent of the depressed patients and 12.5 percent of the control subjects, according to their paper, published in Brain. The effect was even more pronounced in women: 45.8 percent of female patients with major depressive disorder exhibited occipital bending versus only 5.9 percent of women without depression, possibly because women's brains fit more snugly in their skulls than men's do.

Previous studies have also found that occipital bending is more common in patients with schizophrenia. Maller suggests the lobes may wrap around each other when space for brain growth becomes constricted, perhaps because the brain is not doing enough neural pruning—the process by which the brain gets rid of neurons that are no longer needed. Indeed, many other studies have found that depressed brains are hyperconnected. Maller does not know if the finding will have clinical implications beyond helping to diagnose depression, but experts hope that this avenue of research will eventually lead to a deeper understanding of the disorder. “It really suggests some significant biological basis for at least some forms of depression,” says William Hopkins, a professor of neuroscience at Georgia State University, who was not involved in the study.