People suffering from clinical depression, and those at risk from the condition, could benefit from new research.
Experts say that rather than being one disease, clinical depression is a collection of different disorders with one common symptom - low mood.
Over the next five years, scientists will study groups of people who have known depression risk factors.
These include family history of low mood, diseases like heart disease and diabetes and early life problems such as low birth weight or childhood psychological trauma.
Researchers will use memory, reasoning and mental speed tests as well as brain imaging to find out whether specific subgroups of patients correspond to specific disorders.
By studying the groups in this way, scientists hope to be able to identify the causes of depression and this information can be used to develop diagnostic tests and new therapies.
For many people, the symptom of low mood is the most understandable of reactions to loss or stress, yet we remain ignorant of its causes and mechanisms. This means that progress in discovering new and more effective treatments is slow. This Wellcome Trust grant will enable us to make significant progress with this common and disabling condition.
The study, involving researchers from the University of Aberdeen, will also use data from Generation Scotland - a large family-based sample of over 21,000 people.
Clinical depression is a chronic worldwide health problem affecting millions of people and around 13 per cent of the UK population.
Although it is a recurrent problem for many sufferers, little is known about what makes people vulnerable or resilient to the condition.
Depression first affects many in adolescence or in early adulthood and it is often a common cause of suicide.
It is good to see this support for our broadening out of the research on depression, paying closer attention to the thinking skills that alter when people are depressed, and to the brain changes that occur. Our hope is that we will be able to study enough of these factors in a large-enough group of people to start to understand depression better.