The Association Between Depressive Disorder and Chronic Pain
We are introducing a monthly column on mental health disorders and their relationship to chronic pain in order to help pain providers learn more about these disorders, how they are defined, and how the definitions have changed with publication of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).1
In most cultures, the majority of mental health cases go unrecognized in primary care settings.2 About 60% of previously undetected depression cases could have been recognized if the patients had been evaluated for the mental health disorder.3 Numerous studies have documented a strong association between chronic pain and psychopathology.4 Previous research has shown that chronic pain is most often associated with depression, anxiety, and somatoform, personality, and substance use disorders,4 but less is known about the relationship with other conditions, such as schizophrenia spectrum/psychotic, sleep-wake, bipolar, neurocognitive, obsessive-compulsive, and dissociative disorders. The A-Z Mental Health Series will address many of these issues in the coming year, and will culminate in the presentation of a pilot study looking at the prevalence rates of these new DSM-5 disorders among patients who suffer from chronic pain.
Depression and Chronic Pain
Depression is the mental health disorder that has generated the most research and theoretical interest among people who suffer from chronic pain.4 It is the 4th leading cause of disability worldwide.5 The 12-month prevalence of major depressive disorder in the US is approximately 7%, with marked differences by age group (18- to 29-year olds suffer at a rate 3 times higher than those over 60) and sex (females suffer at a rate 1.5 to 3 times higher than males).6
In a recent literature review, the prevalence of pain symptoms in patients with depression ranged from 15% to 100% (mean 65%).7 The mean prevalence for concurrent major depression in patients identified as having pain ranged from 5% to 10% (in primary care)8 to 85% (in dental clinics addressing facial pain)—creating almost a linear increase in the prevalence of depression from community to inpatient medical samples.7
Investigators have found that when a pain condition is more defined (eg, peripheral neuropathy), there is less depression reported compared with medically unexplained pain.9 By contrast, research also indicates that pain symptoms are associated with at least a twofold increased risk for coexisting depression.10 In addition, patients with multiple pain symptoms are 3 to 5 times more likely to be depressed than patients without pain.11 The association between depression and pain also strengthens as the severity of either condition increases.12-14
Depression has been associated with an array of poor pain outcomes and worse prognoses.13,15-17 The prognosis of comorbid depression and pain is poor compared with the prognosis for individuals with depression without pain.18 In fact, a recent population-based study found that persons with concomitant depression and pain initiated more visits to medical providers and had higher total medical costs than persons with only depression.19
Patients with comorbid depression and pain experience more challenges in developing self-management skills.20-22 Depression and chronic pain exacerbate one another, share biological pathways and neurotransmitters, and respond to similar treatments.23,24 Thus, a pain treatment model that incorporates the assessment and treatment of depression seems necessary for optimal outcomes.
How Is Depression Defined?
According to the DSM-5,1 a major depressive episode is diagnosed when 5 or more symptoms have been present during the same 2-week period nearly every day. These symptoms include:
- Changes in thinking, such as difficulties thinking or concentrating and recurring thoughts of death or suicide
- Changes in feelings, such as feelings of worthlessness or guilt and depressed mood or loss of interest and pleasure (or anhedonia)
- Changes in behavior, such as significant distress or impairment in social, occupational, or other area of functioning
- Changes in physical well-being, such as insomnia or hypersomnia, weight loss or gain, psychomotor agitation or retardation, and fatigue or loss of energy
The depressive episode cannot be attributable to another psychological (schizophrenia spectrum or bipolar) disorder, physical condition, or substance use.
The diagnosis of major depressive disorder is based on the presence of a single or recurrent episode, current severity, psychotic features, and remission status. Depressive disorders include several other diagnoses, including premenstrual dysphoric disorder, substance-induced depressive disorder, and depressive disorder due to another medical condition. The DSM-5 also contains a few new depressive disorders, including disruptive mood dysregulation disorder and some modified disorders such as persistent depressive disorder (previously referred to as dysthymic disorder).
The common feature of these disorders is the incidence of sadness, feelings of emptiness and/or irritability, and somatic and cognitive changes that significantly affect the individual’s function. What differs among them is their duration, timing, or presumed etiology.1
The primary difference between the DSM-5 and prior iterations is the abolishment of a bereavement exclusion applied to depressive symptoms lasting less than 2 months following the death of a loved one. The exclusion was omitted for several reasons, including to remove the implication that bereavement typically lasts only 2 months, to recognize it as a severe psychosocial stressor that can precipitate a major depressive episode, to underscore its genetic influence, and to note that it responds to the same psychosocial and medication treatments as non-bereavement-related depression.1
Patients who suffer from comorbid depression and pain often are referred to specialists with expertise in treating either condition rather than to a provider who is comfortable in treating both.7 Therefore, there are a few notable assessments that providers can use to help make treatment decisions. A variety of instruments have been used to screen/assess for depression,7 including the Beck Depression Inventory, the Center for Epidemiological Studies-Depression Scale, the Geriatric Depression Scale, and the Patient Health Questionnaire (PHQ-9). Some of the symptoms of depression and pain also overlap, such as difficulty sleeping, poor concentration, low energy, psychomotor retardation, and decreased interest. Therefore, practitioners should consider only the affective-cognitive symptoms when screening for depression in medical settings.25