By: W. Scott West, MD

Depression is a complex and challenging brain disorder for those who suffer to manage. But, what happens when other illnesses are added to depression? It only creates more challenges. In the medical field, we call this comorbidity, and it happens with frequency. Conditions associated with depression include anxiety, post-traumatic stress disorder (PTSD), substance abuse, pain, and borderline personality disorder (BPD).

Top 4 Most Prevalent Depression Comorbidities: (1, 2, 3)

• 9% of people with depression have substance use disorder (40.8% have alcohol use disorder)
• 52% of people with PTSD have depression
• 8% of people with depression have anxiety
• 5% with depression have BPD.

Plus, 65% of patients with depression report suffering from pain. With these statistics, it is safe to say that depression is often present together with other mental disorders. In fact, patients with depression without comorbidity account for only one-fourth of all patients with that diagnosis.

Diagnoses of these coexisting disorders are based on the fact that the patient has met the requirements for more than one disease in the current operational diagnostic criteria. The presence of comorbidity brings several vital issues to the surface. First, when depression coexists with another mental disorder, these disorders are reported to be more severe than when either is present alone. The frequencies of admissions and suicide attempts are higher, and the prognosis worse in patients with comorbid depression.

Another issue is the temporal relationship between depression and other comorbid mental disorders. There are three ways of considering the order of onset:

1. When depression precedes the other disorder, depression may serve as a causative factor for the subsequent disorder;
2. When the other disorder precedes depression, that disorder may serve as a causative factor for depression; and
3. When depression and the other disorder occur simultaneously, the symptoms of these two diseases may be considered attributable to a different cause(s).

Clinically, we consider why we have these connections. There are areas of the brain such as the frontal cortex, amygdala, hippocampus, cingulate gyrus, nucleus accumbens that have a role in many symptoms that are included in depression, anxiety, and PTSD as well as are considered modulating factors in substance abuse and pain. Also, neurotransmitters such as serotonin, dopamine, norepinephrine, glutamate, and GABA seem to have a role in these diagnoses, perhaps manifesting symptoms based on which area might not be functioning optimally.

Additionally, there are common environmental and situational factors in these diagnoses, including abuse, personal problems, and major illness, as well as the trauma that provoked PTSD.

One of the most critical clinical reasons to screen for comorbidity is that unrecognized depression/anxiety comorbidity is associated with an increased rate of psychiatric hospitalization and an increased rate of suicide attempts. Patients who have depression and anxiety comorbidity have higher severity of illness, higher chronicity, and more significant impairment in work functioning, psychosocial functioning, and quality of life than patients not suffering from comorbidity.

Another factor that brings these illnesses together is the fact that there are common treatments that have been used, including medications, psychotherapies, and now transcranial magnetic stimulation. No treatment works for all people, and everyone needs an individualized approach for each person.

Increased recognition of the high prevalence and negative psychosocial impact of depression and comorbidities will lead to more effective treatment. It is hoped that early and effective intervention will yield long-term benefits. Patients and healthcare providers need to be proactive in recognizing and understanding the comorbidities to determine the best course of treatment to help support a path to achieving a productive, happier and healthier life.

Published: November 4, 2019, PsychCentral.com