Research and treatment approaches to depression.

Depression is a major cause of disability worldwide, but we know little about the underlying fundamental biology. Research is hindered by the difficulties of modelling a disorder of higher cognitive functions in animals. Depression can be understood as the interaction of genetic susceptibility and environmental factors; however, current classifications are purely descriptive. The complexity of this field is best approached by rigorous explorations of known candidate systems in conjunction with the use of genomic tools to discover new targets for antidepressants and to predict therapeutic outcomes.