What Is the Link Between Anxiety and Depression?
Although depression and anxiety are different conditions, they share some common physical and emotional symptoms. They have separate classifications in the American Psychiatric Association’s Diagnostic and Statistical Manual (the DSM-IV), the collection of definitions of mental health problems used by doctors and mental health professionals.
That being said, there is a clear link between anxiety and depression. These two conditions seem to have similar biological and physiological sources and high rates of “comorbidity,” which means that many people suffer from depression with anxiety simultaneously.
Depression/Anxiety Symptoms
What is anxiety? Anxiety is a collection of symptoms, including intense feelings of fear and worry, with physical effects such as increased heart rate and nausea. Anxiety symptoms differ from those of depression, which is associated with emotional symptoms like low mood and loss of interest. Physical effects of depression include disruption of sleep habits and low energy.
While they are two separate conditions, people can experience any combination of anxiety and depression symptoms. Though not officially recognized in the DSM-IV, mixed anxiety and depression (sometimes called “mixed anxiety and depressive disorder,” or MADD) is a commonly diagnosed condition. For example, if you’ve been diagnosed with major depression, you may also have anxiety symptoms. With an anxiety disorder, such as obsessive-compulsive disorder or generalized anxiety disorder, you can also have depression-like symptoms. It’s also possible to experience major depression along with anxiety disorder.
Depression and anxiety disorders have similar environmental sources; stressful situations can trigger or worsen both conditions. A traumatic life event may also act as a trigger, causing an increased risk of depression with anxiety. Comorbidity of depression and anxiety disorders usually leads to more severe symptoms, with more extensive effects on social and professional function.
Biological Foundations
There is also a biological link between anxiety and depression. The brain’s neurotransmitter system is involved in both anxiety and depression disorders. Imbalances of the neurotransmitter serotonin have been implicated in both depression and anxiety disorders. Dysfunction of the brain’s hypothalamic-pituitary-adrenal (HPA) axis is also linked to depression and anxiety, since this mechanism interacts with serotonin levels.
The neurological link between anxiety and depression is further exemplified by the fact that certain medications targeting neurotransmitters (such as SSRIs) can be used to treat symptoms of depression, anxiety symptoms and depression with anxiety.
Resources
Cameron, O. (2007). Understanding comorbid depression and anxiety. Retrieved May 26, 2010, from the Psychiatric Times website: www.psychiatrictimes.com/anxiety/content/article/10168/53896.
Gorman, C. (2002). The science of anxiety. Retrieved May 26, 2010, from the Time Magazine website: www.time.com/time/europe/magazine/2002/0826/anxiety/story.html.
Hirschfeld, R. (2001). “The comorbidity of major depression and anxiety disorders: Recognition and management in primary care.” Primary Care Companion Journal of Clinical Psychology 3(6): 244-254.
McGill University Staff. (n.d.). Serotonin and other molecules involved in depression. Retrieved May 26, 2010, from the McGill University website: thebrain.mcgill.ca/flash/a/a_08/a_08_m/a_08_m_dep/a_08_m_dep.html.
Science Daily Staff. (2010). Biological link between stress, anxiety and depression identified. Retrieved May 26, 2010, from the Science Daily website: www.sciencedaily.com/releases/2010/04/100411143348.htm.
Tyrer, P. (2001). “The case for cothymia: Mixed anxiety and depression as a single diagnosis.” The British Journal of Psychiatry, 179: 191-193.