Clinical depression is a mental illness characterized by long periods of sadness or “emptiness”. These emotions, while a natural reaction to certain events (such as the death of a loved one), will persist for weeks at a time, interfering with the patient’s productivity and ability to feel pleasure. Generally, there are three types of depression. The first is major depression, where the patient experiences intense episodes of depression that come and go. The second is called dysthymia, where the patient experiences long-term depression with symptoms that are less severe. The third is bipolar disorder, where the patient alternates between periods of depression and periods of intense elation (also known as mania).  

A variety of physical symptoms often accompanies depression. These symptoms include insomnia, chronic fatigue, changes in appetite, and even pain. Said pain often comes in the form of headaches, as well as stomachaches, joint pain, limb pain, and back pain. In a primary care setting, many patients with depression will only show physical symptoms. This, unfortunately, frequently leads to misdiagnosis in patients with depression, as the symptoms which they show are often mistaken as signs of a somatic illness, rather than a mental illness (i.e. depression). According to a study led by Kroenke K et al, patients with a high number of physical symptoms are more likely to have a mood disorder than those with fewer physical symptoms. Generally, the worse the chronic pain is, the more intense the depression will be. A study by Ohayon and Schatzberg also indicated that patients with chronic pain were more likely to have suicidal thoughts.  

According to a study by Basbaum AI and Fields HL, pain and depression appear to have a shared neurological pathway. Response to pain is moderated by the neurotransmitters serotonin and norepinephrine. These neurotransmitters also play a key role in the moderation of the brain’s emotional state. A lack of serotonin, for instance, is said to be heavily linked to depression, as well as other mental disorders such as obsessive-compulsive disorder. Norepinephrine, on the other hand, brings our brain into “high alert,” being released by the adrenal glands along with epinephrine (i.e. adrenaline). This is believed to be the main link between mental and physical effects of depression. Thus, the medications which treat the mental symptoms of depression also reduce the intensity of the physical symptoms as well.

The most common method of treating clinical depression is administration of Selective Serotonin Reuptake Inhibitors. These drugs primarily reduce the rate of the brain’s usage of serotonin, allowing the serotonin levels of the brain to increase and thus reduce or even negate the effects of depression. Clinical depression is said to have gone into remission (when the patient no longer experiences depression) when the mental symptoms of depression have disappeared. Unfortunately, many doctors consider a patient to be in remission from their depression even if they continue to experience the physical pain associated with depression. Such patients are significantly more likely to relapse into depression than patients which have stopped exhibiting the physical symptoms of depression. Thus, lingering physical pain may be an indicator that the patient’s depression has failed to go into remission.

Medical research has indicated a significant link between chronic pain and clinical depression. Often, patients will only present the physical symptoms of their depression, and as a result will be misdiagnosed with a somatic illness rather than a mental one. Furthermore, people may mistakenly believe their depression has gone into remission, even when they still exhibit physical symptoms. If you believe that you may have depression, or have had a history of depression, you should be wary of any chronic pain, changes in appetite, persistent fatigue, or insomnia, as these symptoms may indicate the onset of clinical depression. Please contact the National Helpline or any loved ones as well.

References:

Trivedi, Madhukar H. Primary Care Companion to The Journal of Clinical Psychiatry, Physicians Postgraduate Press, Inc., 2004, www.ncbi.nlm.nih.gov/pmc/articles/PMC486942/.

“Clinical Depression.” Clinical Depression | University Health Services, uhs.berkeley.edu/health-topics/mental-health/clinical-depression.

Boeree, George. Neurotransmitters, webspace.ship.edu/cgboer/genpsyneurotransmitters.html.

Kroenke K, Spitzer RL, and Williams JB. et al. Physical symptoms in primary care: predictors of psychiatric disorders and functional impairment. Arch Fam Med. 1994 3:774–779.

Ohayon MM, Schatzberg AF. Using pain to predict depressive morbidity in the general population. Arch Gen Psychiatry. 2003;60:39–47.