Depression is a mental illness characterized by feelings of profound sadness and lack of interest in enjoyable activities. Depression is not the same as a blue mood. It is a persistent low mood that interferes with the ability to function and appreciate things in life. It may cause a wide range of symptoms, both physical and emotional. It can last for weeks, months, or years. People with depression rarely recover without treatment.

The precise cause of depression is not known. It is sometimes difficult to determine if something causes depression, or if it instead is a result of being depressed (ie, does substance abuse result from attempts at self-medicating for depression, or does chronic substance abuse result in depression). Examples of possible causes may be mental, physical, or environmental in nature and include:

• Stressful life events (usually in combination with one or more of the following causes)
• Chronic stress
• Low self-esteem
• Imbalances in brain chemicals and hormones
• Lack of control over circumstances (helplessness and hopelessness)
• Negative thought patterns and beliefs
• Chronic pain
• Heart disease and heart surgery
• Genetic predisposition
• Altered brain structure and function, including after a stroke
• Parkinson’s disease
• Postpartum depression occurs after childbirth
• Seasonal affective disorder is a type of depression or a worsening of symptoms thought to be due to the decreased exposure to sunlight that occurs during winter months, especially in northern climates with longer winters.
• Hypothyroidism
• Anemia
• Cancer
• Substance abuse

A risk factor is something that increases your chance of getting a disease or condition.

Risk factors include:

• Sex: female
• Age: elderly
• Chronic physical or mental illness, including thyroid disease, headaches, chronic pain, and stroke
• Previous episode of depression
• Major life changes or stressful life events (eg, bereavement, trauma)
• Postpartum depression
• Winter season for seasonal affective disorder
• Little or no social support
• Low self-esteem
• Lack of personal control over circumstances
• Family history of depression (parent or sibling)
• Feelings of helplessness
• Certain medications, including medications used to treat asthma , high blood pressure , arthritis, high cholesterol , and heart problems
• Smoking
• Anxiety
• Insomnia
• Personality disorders
• Hypothyroidism

Symptoms of depression are highly variable from person to person. Some people have only a few symptoms, while others have many. Symptoms also vary over time.

Symptoms can change over time and may include:

• Persistent feelings of sadness, anxiety, or emptiness
• Hopelessness
• Feeling guilty, worthless, or helpless
• Loss of interest in hobbies and activities
• Loss of interest in sex
• Feeling tired
• Trouble concentrating, remembering, or making decisions
• Trouble sleeping, waking up too early, or oversleeping
• Eating more or less than usual
• Weight gain or weight loss
• Thoughts of death or suicide with or without suicide attempts
• Restlessness or irritability
• Physical symptoms that defy standard diagnosis and do not respond well to medical treatments

There is no blood test or diagnostic test for depression. The doctor will ask about your symptoms and medical history, giving special attention to:

• Alcohol and drug use
• Thoughts of death or suicide
• Family members who have or have had depression
• Sleep patterns
• Previous episodes of depression

The doctor may also perform a mental status examination or neuropsychiatric evaluation to obtain detailed information about your speech, thoughts, memory, and mood. Questionnaires called depression inventories may be administered. A physical examination and other diagnostic tests can help rule out other causes for your symptoms.

Treatment usually includes medication, psychotherapy, or a combination of the two. Medicine helps relieve symptoms. Psychotherapy helps you learn more effective ways to deal with problems or to identify and resolve the conflicts contributing to your depression.

There may be a need for hospitalization in some cases of severe depression. Depression with psychotic features usually requires hospitalization and use of antipsychotic drugs, such as olanzapine.

Up to 70% of depressed patients find relief from their symptoms with antidepressants. These medications, which can take 2 to 6 weeks to reach their maximum effectiveness, include:

• Fluoxetine (eg, Prozac)
• Sertraline (eg, Zoloft)
• Paroxetine (eg, Paxil)
• Citalopram (eg, Celexa)
• Fluvoxamine (eg, Luvox)
• Escitalopram (eg, Lexapro)

***Please note: In March, 2004, the Food and Drug Administration (FDA) issued a Public Health Advisory that cautions physicians, patients, families, and caregivers of patients with depression to closely monitor both adults and children receiving certain antidepressant medications. The FDA is concerned about the possibility of worsening depression and/or the emergence of suicidal thoughts, especially among children and adolescents at the beginning of treatment, or when there’s an increase or decrease in the dose. The medications of concern—mostly SSRIs (Selective Serotonin Re-uptake Inhibitors)—are: Prozac (fluoxetine), Zoloft (sertraline), Paxil (paroxetine), Luvox (fluvoxamine), Celexa (citalopram), Lexapro (escitalopram), Wellbutrin (bupropion), Effexor (venlafaxine), Serzone (nefazodone), and Remeron (mirtazapine). Of these, only Prozac (fluoxetine) is approved for use in children and adolescents for the treatment of major depressive disorder. Prozac (fluoxetine), Zoloft (sertraline), and Luvox (fluvoxamine) are approved for use in children and adolescents for the treatment of obsessive compulsive disorder. For more information, please visit http://www.fda.gov/cder/drug/antidepressants .

• Imipramine (eg, Tofranil)
• Doxepin (eg, Adapin, Sinequan)
• Clomipramine (eg, Anafranil)
• Nortriptyline (eg, Pamelor)
• Amitriptyline (eg, Elavil)

• Phenelzine (eg, Nardil)
• Tranylcypromine (eg, Parnate)

• Venlafaxine (eg, Effexor)
• Nefazodone (eg, Serzone)
• Mirtazapine (eg, Remeron)
• Bupropion (eg, Wellbutrin)
• Duloxetine (eg, Cymbalta)

Short-term (10 to 20 weeks) therapy can help some depressed people. Psychotherapy is designed to help you:

• Cope with difficulties in relationships
• Change negative thinking and behavior patterns
• Resolve difficult feelings

Electroconvulsive therapy is the use of an electric stimulus to produce a generalized seizure. ECT may be used in people with severe or life-threatening depression. It is also used for people who cannot take or do not respond to antidepressants. It is considered a safe and effective procedure.

Regular exercise has been shown to relieve some of the symptoms of depression. In the absence of physical restrictions, exercise should play an integral role in the overall management of depression.

Phototherapy involves sitting under special fluorescent lights for a prescribed amount of time per day, usually about 30 minutes every morning.

St. John's wort is an herb that is available without prescription. It is widely used in Europe for the treatment of mild to moderate depression. There is conflicting evidence as to its effectiveness, however.

There is also recent evidence that DHEA (a dietary supplement) and an ingredient in fish oil (EPA, eicosapentanoic acid) may help some people with depression, but some experts dispute these findings. Always discuss the use of dietary and herbal supplements with your doctor.

Research suggests that diets high in tryptophan, certain B vitamins , and fish oil may be helpful in relieving or preventing depression. Always discuss the use of such supplements with your doctor.

Vagal nerve stimulation was approved by the FDA in 2005 as therapy for depression that is resistant to multiple trials of antidepressants. VNS involves the surgical implantation of a pacemaker-like device that stimulates the vagus nerve, located in the neck, with electrical impulses.