Sometimes Depression can be caused by other diseases. that is why a complete medical is a good idea.
Hypothyroid ism and Pituitary and thyroid problems generally are often under-diagnosed. (google "Thyroid symptoms" for more info; Mary Shomon's site is good)
Prescription and other drugs too can be a problem. The acne pill given to the young Australian boy is a case in point. Who would expect a pimple pill to cause suicidal depression?
Young males between the ages of 15 to 21-2 are most at risk. The period of the so called "testosterone storm". The chance of males dying at this age is many times greater than females. Take seriously any change in behaviour of (especially male) friends at this age (isolating oneself from friends and family, poor concentration,weight change -up or down, lack of interest in things that usually give pleasure, sadness, happiness (-jolly face sad clown), dropping academic grades, moodiness, preoccupation with death, general anxiety are all pointers.
This is a good website to study the issue more
http://www.beyondblue.org.au/index.a...FR04GAodcTQ4Dg
Depression is the leading cause of non-fatal disability in Australia.