Fig. 1.1
Conceptual diagram of personal factors which may affect disease course
The presence of more serious symptoms of depression such as feelings of helplessness and hopelessness is also likely to negatively impact coping and outcomes.
External or social factors would include the following: access to care, social supports, social status of the disease being faced, understanding by care providers of the etiology of the disease, how the family reacts to the disease, limitations on the disease, how its treatments or the diagnosis itself impinges on career/job performance, and ability/resources to follow through with care (insurance benefits and transportation).
The above may dramatically drive the course of a disease in the individual. For example, a patient diagnosed with multiple sclerosis with significant Uhthoff-related disability (heat intolerance) would be expected to face the anticipation of disease management better if she lived in a cool climate, worked in an air-conditioned building, with low perceived psychosocial stress, resources to work part-time and access to physical exercise options, than would a steel worker who is the sole income earner for her family and with minimal resources. However, it is critical to remember that the weight of each of these factors will differ and despite all risk factors pointing to a patient being high or low risk, any single factor may tip one to an adaptive or maladaptive coping response, disease course and outcome.
Older people are often less dramatically impacted by new medical diagnosis, apparently because they have had more extensive history with health-related problems than the young, and because new health problems are less likely to be perceived as dramatically altering activities of daily living than for the young. Some research suggests that the concept of unmet needs may affect this, as older cancer patients appear to cite unmet needs as less impactful to them than do younger patients [10].
There are several sources of mood disturbance in those struggling with chronic respiratory illnesses. Patients may have preexisting mood disorders, but they may also develop a reactive mood disorder consequent to the limitations caused by their respiratory illness.
In patients hospitalized for COPD, 30-day mortality rates were significantly higher in those with depression and anxiety diagnosis [11]. Willgoss et al. reviewed 10 studies (out of 410 examined) which met criteria for review if prospective, included diagnosed anxiety disorders from a clinical interview using an established psychiatric format, and published in English. Their review suggested that the presence of clinical anxiety was quite high in those with COPD ranging from 10 to 55% (median 17%) in all subject samples [12]. They note that social phobia and specific phobia were particularly prevalent.
Neither the presence of a significant medical condition nor its severity is necessarily associated with the experience of grief, anxiety, or dysphoria. Numerous studies have examined the presence of mood disorders in medically compromised populations but getting to the answer of why some patients are more vulnerable and a reliable model for identifying at-risk patients has been notoriously elusive. It appears that no single factor consistently dictates the course of medical illness. This suggests that it is imperative to carefully evaluate patient risk and protective factors and to tailor treatment to the individual.
Physiological Basis for Depression and Anxiety in Chronic Medical Condition
A properly functioning respiratory system maintains a constant supply of O2 in the cells and removes CO2 to assist in the regulation of blood acidity. Chronic medical conditions not only affect these functions but also negatively affect other body systems that work in coordination with the respiratory system. Disruption of proper respiratory function may negatively impact central nervous system (CNS) function and promote depression and anxiety beyond the effect that any chronic condition has on mood due to impaired quality of life.
Chronic respiratory conditions specifically predispose one to low levels of blood oxygen. Delivery of O2 to cells, including brain cells, is compromised when arterial partial pressure of oxygen declines below 58 mmHg. With the progression of chronic respiratory conditions, oxygenation declines initially during exertion and sleep. However, with progression of the disease, patients remain hypoxic constantly with worsening hypoxia during sleep and exertion. Further, with worsening respiratory disease, gradual chronic retention of CO2 occurs.
In addition to several functional and psychological reactionary bases for depression in patient with chronic respiratory condition (see prior section), physiological derangements resulting from chronic respiratory conditions may cause structural changes in CNS and promote depression due to organic causes. Giltay and colleagues in a longitudinal follow-up of a large cohort showed that low lung volume was associated with increased risk of depressive symptoms in future [13]. Similarly, the prevalence of depressive symptoms was higher in COPD patients with severe lung function impairment [14].
The main question that is not answered is to what degree organic issues related to chronic respiratory conditions promote depression versus the quality of life and nonorganic issues resulting from chronic respiratory conditions.
Hypoxia (both chronic and intermittent) affects the production of various neurotransmitters at the level of central and peripheral nervous systems [15]. Among respiratory conditions associated with hypoxia including sleep-disordered breathing, lower airway diseases, and lung parenchymal diseases, hypoxia is a unifying phenomenon. One of the phenomena examined in the depression literature is “vascular depression.” As an individual ages, the prevalence of MRI-defined subcortical hyperintensities rise as the prevalence of depression rises. Considering that patients with chronic respiratory conditions usually are older and have higher prevalence of cardiovascular and metabolic conditions (diabetes and obesity), it is likely that hypoxia (continuous or intermittent) on the background of cerebrovascular diseases will intensify the local hypoxic conditions and produce more structural changes (MRI-defined subcortical hyperintensities), and thus more predisposition to vascular depression. Interestingly, Van Dijk and colleagues, after adjustment for common risk factors of cerebrovascular disease, identified low O2 and COPD as major risk factors for the presence of periventricular white matter change in a large sample of patients [16]. Role of hypoxia in causing depression is also shown in patients with sleep-disordered breathing [17]. In contrast to hypoxia, it is not clear whether hypercapnia exerts additional detrimental effect on cognition and mood despite higher prevalence of depressive symptoms in severe COPD.
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