How stress and depression can shrink the brain
Depression blocks the formation of new nerve connections in the brain
08:39 GMT, 13 August 2012
Common symptoms of depressive disorder are memory loss and blunted emotional responses
Severe depression and chronic stress can shrink the brain by blocking the formation of new nerve connections, a study has shown.
The effect disrupts circuits associated with mental functioning and emotion.
It could explain why people with major depressive disorder (MDD) suffer from concentration and memory loss, as well as blunted emotional responses.
Several genes involved in building synapses, the connection points between brain cells, were suppressed in people with MDD, scientists found.
This was thought to contribute to shrinkage of the brain's prefrontal cortex, which is known to occur in MDD sufferers.
Researchers in the US analysed brain tissue from patients who had died after being diagnosed with MDD.
They found molecular signs of reduced activity in genes necessary for the function and structure of brain synapses.
Evidence pointed to the involvement of a single genetic “switch”, or transcription factor – a protein called GATA1.
Turning on GATA1 reduced activity of the genes and triggered the loss of brain connections.
Study leader Professor Ronald Duman, from Yale University, said: 'We wanted to test the idea that stress causes a loss of brain synapses in humans.
'We show that circuits normally involved in emotion, as well as cognition, are disrupted when this single transcription factor is activated.'
The research is published in the latest issue of the journal Nature Medicine.
Further studies on rats showed that when GATA1 was switched on, the rodents showed signs of depression. This suggests that loss of brain synapses may be linked to depressive symptoms as well as mental impairment.
'We hope that by enhancing synaptic connections, either with novel medications or behavioural therapy, we can develop more effective antidepressant therapies,' Prof Duman added.