A group of researchers say depression would be better treated if it was classified into 12 different disorders.

There are calls for a major overhaul of the way depression is diagnosed and treated to better recognise its triggers.

A group of international psychologists have challenged the classification of 'major depression' and argue it would be better managed if it was broken down into 12 separate disorders.

"We argue that depression is not a single disease, it is a heterogeneous syndrome, with patients differing remarkably in symptom profile, pathophysiology and treatment responsiveness," says Severi Luoto, a PhD candidate in evolutionary psychology at the University of Auckland

The 12 suggested subtypes, published in journal Brain, Behaviour, and Immunity, are based on the various underlying causes or triggers for the depression, such as illness, loneliness, a traumatic experience or long-term stress.

"If a depressive episode appears to be a response to a adverse life event, clinicians should evaluate whether the symptoms are adaptive or whether the depression episode has exacerbated into pathological depression," said co-author Professor Rantala, a member of the Turku Brain and Mind Center in Finland.

Professor Gordon Parker from UNSW and Black Dog Institute has applauded the paper and says tying treatment to cause is "infinitely better".

He says simply diagnosing someone with 'major depression' is not helpful to the patient.

"It sounds like a diagnosis but it really doesn't mean anything at all in that it just basically homogenises differing types of depression, some of which are biological, some of which are due to psychological factors and some due to stress," said Prof Parker.

"It's no more than a general practitioner saying to a patient they've got major breathlessness; the breathless might reflect asthma or pneumonia."

He says if there are better ways of diagnosing differing types of depression then treatment will become far more appropriate. However he says the 12 named subtypes go too far and need refining.

"In medicine we talk about type 1 and type 2, we don't just talk about diabetes and apply a single treatment," he said.

"We need to move in the same way with regard to depression and have a better way of subtyping and that will lead to more specific and relevant treatments." Professor Parker.

The 12 Depression Subtypes:

* 1 - infection or illness
* 2 - long-term stress
* 3- loneliness
* 4 - traumatic experience
* 5 - hierarchy conflict (eg. bullying at school)
* 6 - grief
* 7 - romantic rejection
* 8 - postpartum depression in women
* 9 - Seasonal Affective Disorder (SAD)
* 10 - chemicals such as alcohol and cocaine
* 11 - somatic diseases such as Alzheimer's, Parkinson's and stroke
* 12 - starvation