Depression vs. Dementia: How Do We Assess? Depressive disorder and dementia are common in older people, and may occur separately or together. Diagnosis is often challenging because of the frequency of symptoms which are common to both disorders. Unfortunately, underdiagnosis of depression results in missed opportunities to improve functioning, decreased quality of life and possibly even increased mortality. Yet, overdiagnosis of depression may result in unnecessary adverse effects of psychotropic medications. This article suggests approaches to differential diagnosis. By Lilian Thorpe MD, PhD, FRCP ementia increases with age, with These include dysthymic disorder, least two contradictory directions of Dan overall prevalence in Canada depressive epi sodes of a bipolar dis- potentially causal influence. One of 8% in those 65 years and older, order, mood disorders secondary to a hypothesis suggests that depression 2.4% in those aged 65 to 74 years, medical disorder (such as hypothy- leads to dementia, and another that 11.1% in those aged 75 to 84 years, roidism), mood disorders secondary suggests that dementia itself leads and 34.5% in those aged 85 years and to a substance, adjustment disorders to depression. older.1 Alzheimer’s disease (AD) is and bereavement. Depressive disor- The depression-to-dementia dir ec - thought to be the most common type der is commonly seen in all stages of tion is supported by evidence that of dementia in all age groups. How - adult life and, while its prevalence is depressive disorder is a risk factor for ever, younger age groups are more slightly lower in the elderly,4 its developing dementia in later life6 and, likely than older age groups to be sequelae are probably greater in more consistent with this, the best-studied diagnosed with other dementias, such frail people, exerting a more deleteri- people with a biological predisposition as frontotemporal dementia and vas- ous effect on functional abilities and to develop AD (those with Down cular dementia.2 even increasing the length of stay for Syndrome) are thought to have a high Major depressive disorder is also hospitalizations related to primary risk of suffering from depression.7 The common, but is only one of a number medical conditions.5 Depressive dis- association between depression and of disorders listed in the Diagnostic order in seniors can occur as part of a later development of dementia is still and Statistical Manual of Mental lifelong recurrent disorder, or it can not completely understood. One possi- Disorders (DSM-IV)3 with prominent present for the first time in old age. It bility is that depression is an early, pro- depressive symptoms (Table 1).3 is frequently concurrent with other dromal phase of dementia,8 and is medical and mental disorders, includ- caused by the same pathophysiologic ing various dementias. initiators that result in dementia. There Lilian Thorpe MD, PhD, FRCP is also evidence that depression is Clinical Professor of Psychiatry, Relationships Between associated with damage to brain loca- and Professor of Community Health and Epidemiology, Dementia and Depression tions integral to cognitive processes, University of Saskatchewan Dementia and depression have a such as the hippocampus, possibly Saskatoon, Saskatchewan complicated relationship, with at by decreasing neurogenesis.9 This The Canadian Review of Alzheimer’s Disease and Other Dementias • 17 Vascular Dementia those with dementia,17,18 although a Table 1 recent Danish study suggests that this DSM-IV Mental Disorders with Prominent Depressive may now have changed, at least in Symptoms3 Denmark.19 Underdiagnosis of dep - • Major depressive disorder ression in demented seniors is clearly • Dysthymic disorder undesirable, as depressive disorders • Bipolar disorder (depressive episode) in the demented elderly have been • Mood disorders secondary to a general medical condition associated with additional burden, as • Mood disorders secondary to a substance (such as a medication) described above. Undertreat ment with antidepressants may also result • Adjustment disorder with depressed mood in over treatment of depression-asso- • Bereavement ciated behaviors with benzodi- azepines and possibly neuroleptics. process may lower the threshold for depression in dementia by using four Adverse effects of benzodiazepines later observable cognitive loss, even- different scales in the same popula- and neuroleptics are well recognized tually increasing age-adjusted demen- tion, and found that between 27.5% and include increased falls, decreased tia rates. Behaviors associated with and 53.4% of people with mild AD alertness, extrapyramidal side effects, depression, such as heavy alcohol and between 36.3% and 68.4% with decreased mobility, decreased func- uses and vascular risk factors like moderate to severe AD were found to tioning and increased mortality. cigarette smoking,10 may also inde- rate positive for depression. Studies Efforts have been made to increase pendently increase later cognitive comparing differences in the preva- the recognition of depression in those loss, while medications prescribed to lence of carefully diagnosed depres- with dementia, and widely used treat depression, especially those sive disorders between matched instruments such as the Minimum with strong anticholinergic effects, demented and non-demented popula- Data Set20 include quality indicators could conceivably have adverse cog- tions are not frequent, but suggest that to alert administrators of patients with nitive effects, although this effect is motivational deficits in dementia may likely depression who are not being likely more transient. be the greatest difference between treated with antidepressants. Review The dementia-to-depression dir- these groups, rather than typical of these quality indicators may pre- ection in the potentially causal rela- DSM-IV major depressive disorder.13 cipitate discussion with attending tionship between the two disorders is However, regardless of the exact physicians, who have the opportunity supported by findings that people prevalence of formally diagnosed to institute appropriate treatment. with dementia appear to have a high- depressive disorder in dementia, it Unfortunately, this process may er prevalence of depression.11 does seem that depressive syndromes also result in an overdiagnosis of However, prevalence rates vary wide- are very common in those with depressive disorder due to the high ly depending on the study population dementia, and that this comorbidity prevalence of behavioral symptoms (psychiatric outpatients, Alzheimer causes increased deficits in function- in dementia such as apathy and reac- registries, old-age homes), instru- ing, increased problematic behav- tive mood symptoms, which overlap ments used, and diagnostic defini- ior,11 increased nursing-home place- with those seen in major depressive tions. Most problematically, the term ment,14 increased caregiver stress,15 disorder. Treatment with antidepres- depression is used to denote different and increased mortality.16 sants is increasingly also known to be clinical concepts, which are not associated with adverse effects, most always equivalent to a diagnosis of Under- and Overdiagnosis of problematically in older, frail popula- DSM-IV major depressive disorder. Depression in Dementia tions. Anticholinergic effects of the Muller-Thomsen et al12 illustrated Depressive disorder has long been tricyclic antidepressants may cause large variability in the diagnosis of thought to be underdiagnosed in confusion, constipation, urinary reten- 18 • The Canadian Review of Alzheimer’s Disease and Other Dementias Depression vs. Dementia tion, and visual-accommodation prob- lems. Postural hypotension may cause Table 2 falls, and cardiac effects are particu- DSM-IV Symptoms of a Major Depressive Episode larly dangerous in overdose. Newer • Depressed mood medications, such as selective sero- • Markedly diminished interest or pleasure tonin reuptake inhibitors (SSRIs) and • Significant weight change venlafaxine, were initially felt to be • Changes in sleep patterns much safer, but have been increasing- • Psychomotor agitation or retardation ly associated with different, rather • Fatigue or loss of energy than fewer, adverse effects. • Feelings of worthlessness, excessive or inappropriate guilt Gastrointestinal side effects and sleep disturbances appear to be more • Diminished ability to think or concentrate common with this group of medica- • Recurrent thoughts of death, suicidal ideation or suicidal actions tions. Recent research has suggested that SSRIs are no less likely than tri- ing behavior, decreased initiative le,26 the Geriatric Depression Scale,27 cyclic antidepressants to cause falls.21 and interest (apathy), psychomotor the Hamilton Depression Rating They are also associated with a higher agitation, and poor concentration (in Scale,28 the Montgomery and Asberg prevalence of hyponatremia,22 and advanced dementia) are common in Depression Rating Scale29 and the most recently research has suggested dementia without depression. Reac - Zung scale.30 Although these scales they increase fragility fractures.23 tive symptoms such as anxiety and vary considerably in how much they Finally, SSRIs have been associated tearfulness are also seen frequently are affected by impairments in lan- with increased apathy,24 even in those in dementia without depression, and guage, awareness and comprehen- who have been appropriately diag- may be related to retained aware- sion, none is useful in