Depression – Diagnosis, Symptoms, and Treatment

Medically reviewed by Dr. Po-Chang Hsu, MD, MS

Medical Professional

Updated - December 14, 2020

Dr. Po-Chang Hsu is a medical doctor from Tufts University in Boston, Massachusetts, interested in pediatrics and neonatology.

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What is Depression?

Depression is a common psychiatric condition characterized by a depressed mood that interferes with social or occupational function.  People usually experience other symptoms, such as problems with sleep, concentration, and appetite.  They also often develop a loss of interest in things that they typically enjoy.  Depression is a significant risk factor for suicide.

What Causes Depression?

Depression is caused by an imbalance in the chemicals in the brain.  One important neurochemical is called serotonin.  Studies show that patients with depression tend to have low levels of serotonin in the brain.  This is important because it affects the treatment of depression – a standard first-line treatment of depression is a class of medications called selective serotonin reuptake inhibitors (SSRIs) - which act to increase brain serotonin levels.

The most common risk factors include:

  • Family history
  • Other psychiatric condition – anxiety, PTSD, bipolar disorder, schizophrenia
  • Alcohol or drug dependence
  • Traumatic brain injury
  • Stroke
  • Other medical conditions (e.g., systemic lupus erythematosus, osteoarthritis, heart disease)
  • Advanced age
  • Pregnancy

Depression is particularly problematic in the elderly population as some of the symptoms of depression overlap with dementia.  It may be difficult to distinguish these two disorders – therefore, depression must always be considered in an elderly patient evaluated for memory loss.

How Common is Depression?

It is one of the most common mental disorders in the United States as it affects approximately 15 million Americans.  The condition is frequently evaluated in the primary care clinic - severe forms of this disease often require referral to psychology and psychiatry specialists.

Approximately 6.7% of American adults experienced at least one episode of depression in 2015.  Depression has a lifetime prevalence of 17% in the United States.  The disease has a higher prevalence in the elderly population.

Signs and Symptoms

The most common symptoms of depression include:

  • Depressed or low mood
  • Changes in appetite
  • Weight loss or gain
  • Impaired sleep
  • Low energy
  • Impaired concentration
  • Loss of interest in normal hobbies & interests
  • Feeling guilty
  • Thoughts of suicide

Several of these symptoms may occur on most days of the week for a sustained period.  By definition, depression interferes with a person’s ability to function socially or work.  The symptoms should not be caused by using a medication or being attributed to another medical condition.


Your doctor will likely order blood tests to exclude medical conditions that can produce symptoms that are similar to depression.  They will typically perform a detailed medication checklist to ensure that your symptoms are not related to prescription drugs.

Laboratory studies usually include a CMP (comprehensive metabolic panel), CBC (complete blood cell count), and thyroid function studies (TSH, free T4).  Depending on your symptoms - you may also be checked for specific conditions such as low vitamin B12, HIV, or syphilis.  They may also perform a urine drug screen to exclude substance abuse as a contributor or comorbidity of depression.

If you are a woman with symptoms of depression and are considering medical treatment, it is always essential to obtain a urine pregnancy test before starting therapy.

Antidepressants and Depression Treatment

Depression is usually treated with the help of a psychologist and psychiatrist.  Psychologists specialize in using behavioral techniques and approaches to improve mood and restore normal function.  They often use a method termed cognitive behavioral therapy to reprogram how we interpret our symptoms – this often leads to improved self-awareness and improvement in symptoms.

Your primary care doctor or psychiatrist may recommend one or more of the following antidepressant medications:

The most commonly prescribed drugs include:

Another option for depression is Wellbutrin XL (bupropion)Wellbutrin (bupropion) may be a particularly good selection in individuals who smoke as it is also prescribed for smoking cessation.

Your doctor may also recommend Oleptro (trazodone) – especially if you are having trouble sleeping. 

Antidepressants generally take at least 2 weeks to a month for patients to notice improved mood and other symptoms.  They should be used cautiously in patients with suicidal thoughts as they may increase the risk of suicide in a small percentage of patients.


  1. Richards D.Prevalence and clinical course of depression: a review. Clin Psychol Rev. 2011 Nov;31(7):1117-25. -
  2. Sullivan PF, Neale MC, Kendler KS. Genetic epidemiology of major depression: review and meta-analysis. Am J Psychiatry. 2000 Oct;157(10):1552-62. -
  3. Adams SM, Miller KE, Zylstra RG. Pharmacologic management of adult depression. Am Fam Physician. 2008 Mar 15;77(6):785-92. -


The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.