On the depression of mice and men

I was listening to NPR last night and caught this bit about a new study of depression drugs:

Scientists have discovered a protein in the brain called P11 that may explain how drugs like Prozac fight depression -- and why they take so long to work.

Continuing...

Researchers have been looking for an explanation by studying precisely how serotonin acts on brain cells. That's hard to do in people. So a team led by Pers Svenningsson of the Karolinska Institute in Stockholm looked at mice with signs of depression. When these mice are held by their tails, for example, they struggle less than normal mice.

Svenningsson and a group of U.S. scientists found that removing P11 from the brains of mice caused them to show signs of depression.

Granted, I'm no scientist, but how do we know that the mice were struggling because they weren't as depressed? Who knows, they may have been trying to wrap the string around their necks to kill themselves.

And isn't it quite a leap to say that not struggling is a sign of depression analogous to human depression? Charles thinks there must be a line missing in the article along the lines of: "Scientists determined the symptoms of depression in mice through a combination of tail-hanging and interviews."

This story is more promising if you look between the lines of its ridiculously reductive analogies, though: thank god researchers are looking beyond seratonin and dopamine as isolated triggers for brain functioning.