Mohammed T. Abou-Saleh

Principles and Practice of Geriatric Psychiatry.Editors: Professor John R. M. Copeland, Dr Mohammed T. Abou-Saleh and Professor Dan G. BlazerCopyright & 2002 John Wiley & Sons LtdPrint ISBN 0-471-98197-4 Online ISBN 0-470-84641-070bThe Aetiology of Late-life DepressionMartin Prince and Aartjan BeekmanInstitute of Psychiatry, London, UKIt is vain to speak of cures or think of remedies, until such time aswe have considered of the causes (Galen)Empirics may ease, and sometimes help, but not thoroughly rootout . . . as the saying is, if the cause be removed, the effect is likewisevanquished (Burton, The Anatomy of Melancholy)Late-life depression, when defined according to the broadcriterion of clinical significance, is a common disorder affecting10–15% of the 65+ population 1,2 . Prevalence rates for majordepression are substantially lower, but this category excludescommon forms of late-life depression, particularly those associatedwith bereavement and physical co-morbidity. Longitudinalpopulation-based studies suggest that incidence and maintenancerates are both high, balanced by a high mortality ratio for thoseaffected.The aetiology of late-life depression remains unclear in somerespects. While many population-based studies have been carriedout in Europe and the USA, most of these have been crosssectionalin design, and have limited themselves to univariateanalyses. The results of these investigations therefore appear aslists of cross-sectional associations, possibly confounded by otherfactors. While causal models can, and have been, inferred fromsuch data, the process is fraught with difficulty and can lead toerrors. More recently, good quality prospective studies have beencarried out that have the potential to clarify the aetiology of thesecommon disorders and inform primary and secondary prevention.AGEThe data on the prevalence of major depression from the USEpidemiological Catchment Area (ECA) survey suggested a lowerrate for those aged 65 (1.0%) than for those aged 45–64 (2.3%)and those aged 18–44 (3.4%) 3 . This relatively low prevalence rateamong the older population was confirmed in a Canadian studyusing similar methodology 4 . These findings have been particularlycontroversial, as they could be taken to imply that the managementof depression may require less resources per capita for theold than for the young 5 . They conflict with the general impressionthat the frequency of depressive symptoms and broader depressivesyndromes either increases 6–8 or remains stable 9 with increasingage. The lay administered Diagnostic Interview Schedule (DIS)used to derive DSM-III diagnoses in the ECA excludes symptomsattributable to bereavement, physical illness or cognitive impairment.The ECA findings have been criticized on the grounds thatthe complex standardized symptoms, and the judgemental processrequired for responding to probes used in the DIS, may exceed thecognitive capacity of many older adults, leading to a systematicresponse bias. This may have been a particular problem wheresubjects were required to attribute symptoms to physical or nonphysicalcauses. Older subjects report as many lifetime depressivesymptoms as younger subjects, but are more likely to attributethem to physical causes, meaning that they are then excluded as abasis of diagnosing depression 10 . However a re-analysis of ECAdata reattributing physical symptoms to psychiatric symptoms didnot lead to a disproportionate rise in major depression among theolder age groups 11 .A further curiosity has been the consistent finding that thelifetime prevalence of major depression seems to be lower forelderly subjects (1.4% for those aged 65 in the ECA survey) thanfor younger subjects (7.5% for those aged 30–44, from the samesurvey). It has been suggested that this may represent a cohorteffect, with successive birth cohorts carrying an increasingpropensity for major depression. More plausibly, this findingmay have arisen from a selective tendency for older subjects not torecall earlier undiagnosed episodes 12 and from the selectivemortality of those most vulnerable to repeated severe episodesof depression 8,13 . A broad review of this area reported similarfindings for most psychiatric diagnoses, including schizophrenia,and concluded that cohort trends cannot be safely extrapolatedfrom cross-sectional data 14 .GENDER AND MARITAL STATUSOne of the clearest and most reproducible findings in psychiatricepidemiology is the apparent excess of depression among women.It has been suggested that the extent of this excess varies acrossthe life course, increasing from menarche into mid-life, and thendeclining gradually into late life 15 . The EURODEP consortium16,17 reported a clear-cut excess of depression symptoms inolder women in population-based studies from 13 out of 14European centres. Interestingly, this association was consistentlymodified by marital status, with marriage being protective for menbut a risk factor among women. Marriage is associated withrelatively low mortality and good health, although this protectiveeffect seems to be stronger for men than for women 18,19 . Inyounger people, marriage also protects against depression amongmen but not among women 20 . In Gove’s 20 study, the excess ofdepression in women relative to men was greatest in marriedpeople. This striking finding has been variously attributed to themundanity of housework and the unfavourable position ofwomen who work outside the home 20 to the differences in thenumber and range of role identities by gender and marital status 21and to the burden of childcaring 22 . Brown et al. drew attention tothe lack of satisfaction with the married state expressed byPrinciples and Practice of Geriatric Psychiatry, 2nd edn. Edited by J. R. M. Copeland, M. T. Abou-Saleh and D. G. Blazer&2002 John Wiley & Sons, Ltd