Common symptoms include persistent low mood, loss of interest and enjoyment, sleep and appetite changes, guilt or self-criticism, poor concentration, and reduced energy.
Affects 5% to 10% of patients in the primary care setting.
Risk factors include prior depression and a family history of depression. Recent bereavement, stress, or medical illness may contribute.
For screening and diagnosis, self-rating forms are helpful, but clinical diagnosis is essential. Positive screening should trigger full history, mental status exam, treatment, and follow-up.
Most patients respond well to treatment with antidepressants, psychotherapy, or a combination of both.
Suicidal ideation can occur before and peak during treatment, so early close follow-up is advised.
Depressive disorders are typically characterized by persistent low mood, loss of interest and enjoyment, neurovegetative disturbance, and reduced energy, causing varying levels of social and occupational dysfunction. Depressive symptoms include depressed mood, anhedonia, weight changes, libido changes, sleep disturbance, psychomotor problems, low energy, excessive guilt, poor concentration, and suicidal ideation. In some cases the mood is not sad, but anxious or irritable or flat. 
Major depressive disorder is characterized by the presence of at least 5 symptoms and can be classified along a spectrum of mild to severe. Severe episodes may include psychotic symptoms such as paranoia, hallucinations, or functional incapacitation.
Subthreshold (minor) depression is characterized by the presence of 2 to 4 depressive symptoms, including depressed mood or anhedonia, of greater than 2 weeks in duration.
Persistent depressive disorder (dysthymic disorder) is characterized by at least 2 years of 3 or 4 dysthymic symptoms for more days than not. Dysthymic symptoms are depressed mood, appetite change, sleep disturbance, low energy, low self-esteem, poor concentration, and hopelessness.
Psychiatry and Behavioral Sciences
The Johns Hopkins Hospital
DFM declares that he has no competing interests.
Dr Dean F. MacKinnon would like to gratefully acknowledge Dr Roger S. McIntyre, Dr Tonya Fancher, and Dr Richard Kravitz, the previous contributors to this monograph. RSM has received research funds from Stanley Medical Research Institute and National Alliance for Research on Schizophrenia and Depression (NARSAD). RSM is on the advisory board for AstraZeneca, Bristol-Myers Squibb, France Foundation, GlaxoSmithKline, Janssen-Ortho, Solvay/Wyeth, Eli Lilly, Organon, Lundbeck, Biovail, Pfizer, Shire, and Schering-Plough. RSM is on the Speakers Bureau for Janssen-Ortho, AstraZeneca, Eli Lilly, Lundbeck, Biovail, and Wyeth. RSM has received research grants from Eli Lilly, Janssen-Ortho, Shire, and AstraZeneca. RSM has received travel funds from Bristol-Myers Squibb. TF declares that she has no competing interests. RK has received research grants from Pfizer on non-depression-related topics.
St Vincent's Hospital
SM declares that he has no competing interests.
Department of Psychiatry and Psychotherapy
Medical University of Vienna
DW has received lecture fees from CSC Pharmaceuticals, GlaxoSmithKline, and Pfizer, and has served as a consultant for GlaxoSmithKline.
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