ROGER HARRIS / SCIENCE PHOTO LIBRARY
Your brain looks different if you have depression. But many of the differences seem to be caused by depression, rather than precede it.
When neuroscientists compare the brains of people with and without depression, there are common dissimilarities. For example, people with depression tend to have a smaller hippocampus, a brain region important in forming memories.
But it has been difficult to work out whether such differences cause the symptoms of depression or whether they result from …