Major depressive disorder is a serious and often chronic health proble
m that affects a significant portion of the population, It is associat
ed with Substantial morbidity and mortality, Early diagnosis and treat
ment of major depressive disorder significantly improves functioning,
quality of life, and prognosis, However, because diagnosing the disord
er can be difficult, depression frequently goes undetected and untreat
ed. Clinicians must remember that the experience of and ability to com
municate depressive symptoms can be affected by age, culture, and gend
er. They must also be aware that many patients complain of somatic sym
ptoms rather than allude to feelings of depression. Questions for clin
icians to consider when making a differential diagnosis include: Is th
e patient experiencing true depression or a normal reaction to a stres
sful life event? Can the depression be linked to an existing medical c
ondition or drug therapy? Does the patient actually have another psych
iatric illness that shares some features with depression? Patients mee
ting the diagnostic criteria for major depression can be further class
ified into subtypes of depression that carry prognostic and treatment
implications.