Hypercortisolaemia has long been recognised as a marker for depression, where the hypothalamic-pituitary-adrenocortical axis is shown to be constitutively active (; ). In spite of some clinical studies describing higher concentrations of the mineralocorticoid hormone aldosterone in depressed patients (; ), little attention has been given to the role of aldosterone in depression. The first and potentially direct evidence for aldosterone involvement in the development of depressive behaviours comes from recent animal studies. Specifically, sub-chronic treatment with aldosterone induced anxiety () and depression-like behaviours which were concomitant with gene expression changes in the hippocampus that may be relevant to major depression (). The data suggests that aldosterone, via activation of mineralocorticoid receptors (MRs) or other mechanisms may be causally involved in the pathophysiology of at least some forms of depression.