EARLY digestive problems may hardwire the brain for depression.
While gut problems are often linked with depression, they are generally assumed to arise from hormones released because of alterations in mood. Pankaj Pasricha and colleagues at Stanford University in California believe it might be the other way round.
Pasricha's team gave young rats a mild stomach irritant, then tested them for symptoms of depression at 10 weeks old. The rats showed more signs of depression and higher levels of stress hormones in the brain than healthy rats. Jamming signals from nerves in the gut made no difference to their depression, suggesting that ongoing gut pain wasn't the trigger. Blocking receptors to stress hormones in the brain did alleviate the effects (PLoS One, DOI: 10.1371/journal.pone.0019498). Next Pasricha wants to explore the role of the vagus nerve, which allows the gut to communicate with the brain.
Some people are more susceptible to depression than others, however. Understanding genes involved in the disorder could help to explain why. Gerome Breen at King's College London and colleagues found strong evidence of a genetic link in cases of severe depression. They scanned the genomes of individuals from over 800 families with a history of depression.
The results highlight abnormal variations in genes on chromosome 3 (American Journal of Psychiatry, DOI: 10.1176/appi.ajp.2011.10091342). A group from Washington University in St Louis, Missouri, came to the same conclusion - the first time such a finding has been replicated.
Understanding which pathways may be affected by these variations, could help personalise medicine. At the moment only half of the people given medication for depression respond at all.