Understanding why serotonin does not cause depression

Allan Young, one of the co-authors of the recent article that indicated that serotonin is implicated in depression (see last post), is quoted in Herald Scotland (see analysis article) as saying that “Any criticism of the chemical imbalance theory truly misunderstands why it was developed and used by researchers and clinicians”. I’m not quite sure what he means by this. As I understand it, the motivation to continue the serotonin hypothesis is to encourage people to take their antidepressant medication. How people have understood the serotonin hypothesis (chemical imbalance theory) is that depression is caused by low serotonin. Young says this theory is too simplistic. But I’m not sure what he believes instead.

He suggests the theory was developed to explain how “brain changes occur in depression in a more accessible way”. Again, it’s not clear what he means by this. But this seems to be the crux of the problem. Are the brain changes in depression any different from ‘normal’? Depression is a personal condition. Of course it’s mediated by the brain. That’s commonsense and not rocket science. People don’t need a chemical imbalance theory to understand that.

Young's convinced that “brain changes do occur in the brain of depressed people”. He seems to be saying that these changes cause depression. He’s got muddled that people are their brains (eg. see previous post). Of course I have a brain. If I was depressed I would still have a brain. But that brain is not me, whether I’m depressed or not. It doesn’t cause my depression.

The conclusion of the umbrella review by Moncrieff et al was that there is no convincing evidence to support the theory that depression is caused by low serotonin. Young says this conclusion is wrong. It isn’t! Psychiatrists like Young need to move on from an outdated, misguided physical disease model of mental illness. Otherwise he won’t understand why the serotonin theory of depression needs debunking, even the less simplistic version he wants to promote, whatever that is.