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Last Updated: Mar 1, 2019


Depression is a mood disorder characterized by debilitating feelings of sadness and hopelessness that interfere with normal activities of day-to-day life. Depression commonly develops in young adults and adolescents, but the disorder can also occur in children.

Types of Depression

  • Major depressive disorder, also known as major depression, is characterized by profound symptoms of sadness that impair a person’s enjoyment of daily life. The disorder can interfere with work, disrupt sleep, affect appetite, and harm a person’s wellbeing.
  • Persistent depressive disorder is a prolonged form of depression that lasts for at least two years.
  • Psychotic depression is associated with delusions, hallucinations, and an abnormal sense of reality (psychosis).
  • Postpartum depression occurs in certain women after giving birth and is attributed to fluctuations in hormone levels, physical changes, and feelings related to the responsibility of caring for an infant.
  • Seasonal affective disorder (SAD) is a type of depression that occurs during the winter when there is less sunlight.
  • Bipolar disorder (manic depressive illness) occurs when a person has a cyclical disorder characterized by episodes of major depression and episodes of extreme highs (mania).


A combination of various factors can trigger people to develop depression. Such factors include genetic predisposition, environmental factors, hormones, brain chemicals (neurotransmitters), trauma, relationship problems, and stressful life events (such as divorce or loss of a job). For unknown reasons, women have a much higher risk of developing depression than men.

Studies have shown that certain areas of the brain that shape our mood, memory and behavior can have an altered appearance in those suffering from depression. For instance, some studies have revealed the hippocampus to be physically smaller in people with depression, and suggest that the degree to which it is smaller may correspond to the frequency of symptoms. Whether these physical changes in part lead to depression or are instead an effect of the disorder is still undetermined.

Frequently, people with serious medical problems also have depression. Neurological disorders, thyroid diseases, cancer, infections, and metabolic disorders often lead to depression symptoms.

hippocampus highlighted in the brain


Common signs and symptoms of depression include the following:

  • Prolonged sadness
  • Hopelessness and pessimism
  • Loss of interest in activities and hobbies that were once enjoyable
  • Sleep difficulties (insomnia or excessive sleeping)
  • Persistent fatigue
  • Indecisiveness
  • Difficulty concentrating
  • Loss of appetite or overeating
  • Suicidal thoughts
  • Excessive guilt
  • Inability to function at work
  • Poor hygiene and self care
  • Alcohol or substance abuse.


In some patients, depression is difficult to diagnose because it may mimic other medical conditions. Major depression is often unrecognized in the elderly, for whom the disorder is frequently mistaken for the signs and symptoms of aging. When depression is suspected, a physical examination and lab tests should be performed to rule out a medical illness.

A psychiatric assessment includes a thorough evaluation of a patient’s thoughts and behaviors; history of other psychiatric disorders; current stressors; major life events; occupational history; relationships; family history of mental illness; and use of illicit substances and alcohol. Special attention is given to the presence of thoughts about suicide and signs of poor self-care.


Whether patients with depression are treated in a hospital or an outpatient setting depends on the severity of their symptoms and their risk of harming themselves or others. Hospitalization is frequently indicated for patients who are deemed at a high risk of suicide or have extremely impaired self-care.

Antidepressant Medication

The choice of antidepressant medication depends on the drug’s side effects and a patient’s response to treatment. Usually patients need 4 to 6 weeks of treatment before a physician can determine whether a specific therapy is effective. Research shows that some patients, especially adolescents, may have an increased risk of developing suicidal thoughts while taking antidepressant medications, so patients need to be carefully monitored after any medication is initiated.

  • Selective serotonin reuptake inhibitors (SSRIs) work by affecting the level of serotonin, a brain chemical (neurotransmitter) that is involved in regulating mood. Common SSRIs include fluoxetine (Prozac®), sertraline (Zoloft®), escitalopram (Lexapro®), paroxetine (Paxil®), and citalopram (Celexa®). These newer medications are popular because they have fewer side effects than older antidepressants.
  • Serotonin and norepinephrine reuptake inhibitors (SNRIs) work by modifying the levels of neurotransmitters serotonin and norepinephrine. Duloxetine (Cymbalta®) is an example of an SNRI.
  • Norepinephrine and dopamine reuptake inhibitors (NDRIs) also alter neurotransmitter levels. NDRIs include bupropion (Wellbutrin®).
  • Tricyclic antidepressants are older, rarely used drugs with serious adverse effects.
  • Monoamine oxidase inhibitors (MAOIs) are rarely used medications that are effective for depression but interact adversely with certain foods.


Psychotherapy is also called talk therapy, and for some patients with mild to moderate forms of depression, psychotherapy alone is the initial treatment. A combination of antidepressant medication and psychotherapy is usually required for patients with moderate to severe forms of depression.

  • Cognitive-behavioral therapy (CBT) helps patents modify their negative thought patterns.
  • Interpersonal therapy (IPT) focuses on managing troubled relationships that are contributing to depression.

Other Therapies

  • Electroconvulsive therapy (ECT) delivers an electrical impulse (shock) to the brain and causes a brief seizure that changes the brain’s chemistry. Prior to an ECT treatment, an anesthetic medication is administered to prevent the patient from feeling the shock sensation. For maximal effectiveness, ECT treatments must be repeated multiple times.
  • Bright light therapy is commonly prescribed for seasonal affective disorder.

Lifestyle Changes

Patients are advised to engage in regular exercise, which has been shown to significantly reduce depression symptoms. Additionally, proper sleep and diet are recommended. Patients with depression should avoid alcohol and illicit substances.

Alternative Medicine

S-adenosyl methionine (SAMe) and St. John’s wort may help reduce mild forms of depression. These over-the-counter treatments are associated with potential risks, and more research is needed to determine their efficacy.

Education of the Family

With the patient’s consent, family members are educated about depression and early signs of relapse. Patients with supportive relationships tend to achieve better outcomes.


Although there is no specific method of preventing depression, patients may decrease the risk for major depression by controlling stress and maintaining relationships with family and friends. Individuals with early signs of depression should be treated promptly to prevent severe debilitation.


  • What is Depression? National Institute of Mental Health website. Accessed June 26, 2014.
  • Gelenberg AJ, Freeman MP, Markowitz JC, Rosenbaum JF, Thase ME, Tivedi MH, Van Rhoads RS. Practice Guideline for the Treatment of Patients With Major Depressive Disorder, Third Edition. American Psychiatric Association Practice Guidelines. website. Accessed June 26, 2014.
  • What causes depression? Harvard Medical School. Accessed July 9, 2014.
  • Cole SA, Christensen JF, Raju Cole M, Cohen H, Feldman MD. Chapter 22. Depression. In: Feldman MD, Christensen JF. eds. Behavioral Medicine: A Guide for Clinical Practice, 3e. New York, NY: McGraw-Hill; 2008.

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Tina Shahian, PhD

Tina is a writer for Innerbody Research, where she has written a large body of informative guides about health conditions.


A communication specialist in life science and biotech subjects, Tina’s successful career is rooted in her ability to convey complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. Tina Shahian’s Linkedin profile.


In her spare time, Tina enjoys drawing science-related cartoons.