Depression is an increasingly common problem of our time. The WHO lists this condition as a major cause of 'social disability'. It is estimated that around 300 million people worldwide struggle with depression - regardless of age, race or gender. It is not surprising, therefore, that researchers are trying to find indicators that can in selecting an effective treatment that will enable the return of normal cognitive function and regulated mood. It is important to remember that depression is not a temporary mood disorder, but a serious condition that hinders daily functioning and social life.