Researchers in Britain and China, using brain imaging, found depression frequently seems to uncouple the brain's so-called hate circuit.
Jianfeng Feng of the University of Warwick and colleagues used functional magnetic resonance imaging to scan the brain activity in 39 depressed people -- 23 female, 16 male -- and 37 control subjects who were not depressed -- 14 female 23 male.
Earlier research by Semir Zeki of University College London found a circuit that seemed to connect three regions in the brain -- the superior frontal gyrus, insula and putamen -- when test subjects were shown pictures of people they hated, which Feng said may be thought of as a hate circuit.
The current study, published in the journal Molecular Psychiatry, found the fMRI scans revealed significant differences in the brain circuitry of the two groups.
"The results are clear but at first sight are puzzling as we know that depression is often characterized by intense self loathing and there is no obvious indication that depressives are less prone to hate others," Feng said in a statement. "One possibility is that the uncoupling of this hate circuit could be associated with impaired ability to control and learn from social or other situations which provoke feelings of hate toward self or others."