Key points

Depression in older people is among the most disabling of conditions.

Depression is the most common and treatable mental disorder in later life.

Depression in older people is undertreated in absolute terms and compared to younger adults.

Depression is a heterogeneous disorder: objectively defining sub-types will be essential to developing more specific treatments.

1 Introduction

Depression is a term that means many things to many people. Consequently, any discourse could be criticized for being non-specific and over inclusive, or too specific and exclusive. Therein lie many of the difficulties of understanding and discussing the subject. Colloquial use describing a normal emotion of sadness is different from medical diagnostics, though there is dispute about diagnostic criteria, the arbitrary threshold when normal becomes pathological, and whether current diagnostic criteria are discriminating (1). As a clinical syndrome, diagnosis depends entirely on the clinician’s interpretation of symptoms.

Classifications give the impression of a single condition rated mild to severe by cumulative symptom score. Yet, depression is clearly a heterogeneous group of disorders with overlapping core features of anhedonia, fatigue, loss of interest, and low mood. It may occur with biological symptoms (appetite, weight, sleep), with psychotic symptoms (delusions, hallucinations), with motor symptoms (retardation, agitation); as variants like psychotic, melancholic, bipolar, brief, organic, major, and minor; with severity from mild to severe; and as a single episode or recurrent.

Medical co-morbidities, typical of older people, complicate matters further, because it is often difficult to know whether symptoms, particularly biological ones, should be attributed to depression or the physical condition. In a study of medical admissions over age 70, fine changes to the application of diagnostic criteria—removing biological symptoms and substituting psychological symptoms—reduced the prevalence from 20.7% to 15% (2).

Nevertheless, a condition that can cause profound loss of function and capability, associated with mood change, physical symptoms, impaired intellectual function, and altered thought and perception has been recognized since the time of Hippocrates and Galen. The condition was described vividly in the mid-nineteenth century by Esquirol (3), who reported how patients succumbed to malnutrition and infection; it was first captured in the English language by Robert Burton’s autobiographical account of melancholia (4).

2 Incidence and impact

Depression is among the most disabling of conditions. In 2008 (5) it was declared the third highest global cause of loss of disability-adjusted life years, the highest in middle- and high-income countries, and projected to be the highest globally by 2030. Depression is associated with a decrement in health greater than common chronic diseases (6). Further, it complicates the treatment of other medical conditions by virtue of apathy, loss of engagement, non-compliance, and secondary physical disability. As a risk factor for coronary heart disease, depression is reported to be as significant as diabetes and smoking (7). There is evidence that depression is also a risk factor for stroke, colorectal cancer, back pain, irritable bowel syndrome, multiple sclerosis, and possibly type II diabetes (8). Untreated depression in older people approximately doubles mortality rate (9). Depression accounts for over 80% of deaths by suicide of older people (10). Deliberate self-harm in older people usually represents a failed suicide attempt (very different from younger people when mental illness is rarely implicated and self-harm is impulsive) and the recognized determinants of suicide are evident (11). The risk of suicide after deliberate self-harm increases markedly with age (12), especially if there has been a previous episode (13). A prospective study of self-harm in adults over age 60 found the risk of suicide was 67 times higher than the general population in the following 12 months, with men over age 75 at highest risk (14).

3 Depression in the older person

The symptoms of depression in later life appear similar to younger age groups (although, it is true, older people manifest more somatic symptoms and more agitation, experience less guilt and less reduction of sexual libido, and their symptoms tend to be more severe) (15). Nevertheless, we cannot assume, without question, that depression is the same for both age groups. Indeed, a criticism of approaches to late-onset depression would be the extrapolation of an evidence base from research with younger populations. The trend in classifications and some interpretations of equality that disregard age as a variable should not make us complacent in believing that late-onset disorders can be understood and approached in the same way as those of younger people. To do so may be indirect age discrimination (16) and, even if symptoms are similar, a very different psychosocial context and co-morbidity alters management (Box 9.1).

Box 9.1 Characteristics of depression in older people compared to younger adults

symptoms—more somatic, agitation, and cognitive impairment

• less guilt and less loss of sexual libido

• tending to more severe

higher suicidality and greater risk of suicide after deliberate self-harm

vascular brain changes more common

more often complicated by multimorbidity

longer duration of maintenance treatment to prevent relapse

greater sensitivity to adverse effects of antidepressants

less often diagnosed or referred to psychiatry

less research done on older people

less quality guidance available.

There are substantially fewer studies of depression in later life and, it could be argued, the treatment evidence base for an older population with multiple co-morbidities barely exists (other than at the level of clinical experience), because people with co-morbidities on multiple drug treatments are usually excluded from clinical trials. One could also argue that this is when specialists, working with a familiar set of circumstances, become important.

4 Epidemiology and causes

The EURODEP collaboration found the prevalence of case-level depression—that is, depression suitable for intervention—varied from 8.8% to 23.6% using the same standardized diagnostic tool in community studies of people over age 65 years in Europe (17). A systematic review of all community studies reported prevalence of 0.4–35% with an average of 13.5% (1.8% severe) in those over age 55 (18).

Explanations of these variations elude us, though there is broad agreement that being widowed or divorced, having low educational attainment, poor self-rated health, functional and cognitive impairment, poor social networks, and socio-economic adversity all increase the likelihood of depression. Protective factors include good physical health, a confidante, marriage for males, a strong social network, and religious faith. Genetics probably play a part, though not by single-gene effects, and probably less so for late-onset depression; further, genetic effects are likely to vary by subtype.

By virtue of an ageing population it is predicted that the number of people in England over age 75 with depression will increase by 30% from 2008–2026. For those over 85, the number jumps to 80% (19).

The amine hypothesis of depression (20) was a milestone in the history of psychiatry, providing both a biological explanation and the scientific basis for drug treatment. Further understanding came from recognizing the social determinants of adversity and life events (21), cognitive theories of depression (22), and the relationship with physical illness, disability, and handicap (23). More recently, vascular depression describes a sub-group of late-onset cases associated with extensive ischaemic changes (particularly frontal and basal ganglia) found on brain magnetic resonance imaging (24).

That all of these provide credible frameworks for understanding and treating depression in different people attests to the heterogeneity of this condition.

4.1 Treatment and outcome

Depression can be self-limiting. More than 100 years ago, and before antidepressant treatments, the father of modern psychiatry, Emil Kraepelin (25), noted that one third of patients with melancholia made a complete recovery (these were severe or psychotic asylum cases). Due to the seriousness of suicidal thinking, Kraepelin thought all needed treatment in the asylum. In the seminal study into the mental disorders of late life, Roth (26) provided elegantly descriptive evidence that these were not all variants of senile dementia. Rather, depression differed from the others: patients with depression showed the ability to recover and be discharged from the asylum. Roth reported that 33% of depressed patients admitted in 1934 or 1936 (before treatment) were discharged within six months, whereas the rate climbed to 58% in 1948 and 1949 after introduction of electroconvulsive therapy (ECT), the first antidepressant treatment.

More recently, a community study of essentially untreated depressed elders found 22% of those completing five-year follow-up were recovered (27). A longitudinal primary-care study of people over age 55 found that the median duration of a major depressive episode was 18 months. Although no more than 40% of the patients received treatment, 35%, 60%, and 68% recovered at one, two, and three years, respectively (28).

Treating depression in later life follows the same principles as for younger people. Antidepressants and psychological approaches are equally as effective for older people (29, 30). Antidepressant monotherapy response is 50–60%; number needed to treat ranges from four to eight depending on antidepressant class, but the majority of antidepressant trials with older people exclude those with physical illness (29). Debate continues about the superiority of one antidepressant class over another and there is currently no reliable way to predict who will respond to which treatment (31). Choice of antidepressant is often determined by side-effect profile, which varies by class; all present risks with older people (32). Detailed discussion of these differences is beyond the scope of this chapter.

Sertraline and citalopram have, possibly, the best risk-benefit ratio (33) and are least likely to affect the p450 enzyme system and interact with other medications. A caveat is that citalopram causes dose-related prolongation of the QTc interval (34). An early response predicts the best recovery (35). Response to ECT is at least as good for older people who show an improvement in cognitive function proportionately greater than younger subjects (36, 37). A systematic review suggests that 52% who fail to respond to a single antidepressant will respond to alternative pharmacotherapy, though the authors note the paucity of good quality studies and an absence of guidance in comparison to younger adults (38). The time involved working through these alternatives can be frustrating and disheartening for patients.

Psychological treatments should be used for mild depression but the best outcome for moderate and severe depression is achieved by combining psychological and pharmacological treatments (39). Following recovery, antidepressants need to be continued longer with older people; active treatment confers benefit over placebo up to 21 months with two and half times reduction of relapse rate (40). Up to 90% of those maintained on placebo have recurrence within three years but with prophylaxis this is more than halved (41). It is a remitting and relapsing illness for most.

Despite this, depression in later life is far less likely to be treated than in younger adults. Not all older people discuss depression with their physician. Instead, most attend primary care with physical complaints, and some studies find that the diagnosis is often missed in primary care. Even when recognized, depression in the older person is less likely to be treated or managed by referral to psychiatry services (42, 43). It is estimated that around one in six older depressed people in the UK receive treatment of any sort. Whereas 50% of depressed younger adults are referred to psychiatry services, the rate is only 6% for older people (44). So, for every 1 million depressed older people, 850,000 receive no treatment—approximately 2.5 million nationwide. That 4% of the depressed in a community study of older people were in receipt of antidepressants while 80% were receiving prescriptions for other medical conditions (45) suggests that depression prompts less of a response from clinicians than physical conditions.

That adversity and illness become common in later life may tempt clinicians to conclude that depression is a natural reaction not needing treatment. Such stereotypical perception that depression is just a consequence of old age is not upheld by community studies (46). The old distinction between reactive and endogenous depressions, implying the former was natural and the latter in need of treatment, was dispelled once it was shown that both respond equally to treatment. Aetiology informs the type of treatment, not its need, just as the cause of pain informs the method, not the need of pain relief.

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