INTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, VOL. 6: 4774.3 1 (1991)

EDITORIAL

The prognosis of depression in old age: good, bad or indifferent?

DAVID AMES Senior Lecturer in the Psychiatry of Old Age, University of Melbourne Department of Psychiatry, 7th Floor, Clinical

Sciences Building, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia

AND

NICHOLAS ALLEN Clinical Psychologist, University of Melbourne Department of Psychiatry, 7th Floor, Clinical Sciences Building, Royal

Melbourne Hospital, Parkville, Victoria 3M0, Australia

Depression has been described by Henry Brodaty as the ‘bread and butter’ of old age psychiatry. In four community surveys of old people depression outranked dementia in frequency by a factor of at least three to one (Copeland et al., 1987a and b; Livingstone et al., 1990), and depression is the commonest diagnosis among those aged 65-75 who present to psychiatrists (Post, 1982). After the land- mark study of Roth (1955) affective disorders in the elderly were regarded as having a relatively good prognosis, but this comforting dictum was undermined by the worrying finding of Murphy (1983) that only 35 per cent of 124 subjects treated for a first depression in old age were well one year after presentation. Many old age psychiatrists felt that these findings were at variance with their own practice, and at least two set out to refute them (Baldwin and Jolley, 1986), but eight years after the publication of Murphy’s study there are plenty of unanswered questions regarding the prognosis of depression in old age.

It is important to have accurate data regarding the prognosis of common disorders under current treatment regimes. Patients and their relatives are entitled to accurate statements about likely out- come. Factors associated with good and poor out- comes may point to ways to prevent the disorder under consideration or improve its management, and unless we know the prognosis of a condition as currently managed, we cannot tell whether puta- tive improvements in treatment and care are effec- tive in improving outcome. Without accurate research data clinicians tend to fall back on clinical

impression to form views of the likely outcomes of treated disorder in individual patients. Judge- ment heuristics and biases (cognitive short cuts used to make quick approximate judgements) have a tendency to cause errors in probability judge- ments which violate statistical laws in predictable ways (Schwartz and Griffin, 1986). Subjective prob- ability estimates are partly determined by the ease with which events similar to those under consider- ation can be brought to mind, the so called avail- ability heuristic. The salience of particular cases makes them easier to retrieve from the memory than others, and it may be that clinicians find suc- cessfully treated cases more salient because of the greater satisfaction inherent in the management of such patients. Normal people tend to emphasize positive events in their memories and psychiatrists are likely to prove no exception to this rule. This might help to explain the general surprise at Mur- phy’s findings, and account for her interesting observation that optimistic case-note entries were often at marked variance with the findings of struc- tured follow-up interviews conducted by a clinician who was not involved with the treating team. The views of clinicians are a useful hypothesis generat- ing mechanism, but hypothesis testing requires research to distinguish between those things every- body knows to be true, which are true, and those things everybody knows to be true which are false!

Since the advent of electroconvulsive treatment and antidepressant drugs it has been considered unethical to conduct long-term outcome studies on untreated individuals with depressive illness.

0 1991 by John Wiley & Sons, Ltd.

478 D. AMES AND N. ALLEN

Naturalistic observational research, such as that undertaken on involutional melancholics by Hoch and MacCurdey (1922), is unlikely to be repeated. Over the last three decades, research on the progno- sis of depression in old age has concentrated upon patients with the more severe forms of affective disorder presenting to psychiatrists for treatment. There is far more data relating to patients treated in hospital than to those treated as outpatients. Patients treated in primary care have received scant attention, and although reports of follow-up on depressed subjects detected in epidemiological sur- veys are starting to appear, they are few in number.

Cole (1990) has provided an excellent critical review of studies on the prognosis of depression in old age, published in English and French, between 1950 and mid-1989. The criteria for study selection included a sample of at least 25 patients, inclusion of only patients aged above 60, mean fol- low-up of at least one year, and descriptions of patients’ mental states during follow-up. The most significant finding of his enquiry was that all ten of the studies reviewed had serious multiple flaws when subject to the six evaluation criteria for pro- gnosis of disease propounded by the Department of Clinical Epidemiology and Biostatistics at McMaster University Health Sciences Centre (1981). No study had blind outcome assessment, only one gave a clear definition of relapse, only one other formed an inception cohort designed to identify depression at an early and uniform point in its course, eight lacked adequate description of referral pattern and consequent sample bias, two failed completely to account for interference upon prognosis by extraneous factors and in one study more than 20 per cent of the cohort were lost to follow-up. To these criticisms could be added the observation that three studies lacked any operatio- nal diagnostic criteria, only one used a structured interview to assess subjects, and at least two were retrospective in design. The statistical power of the studies was low because of small sample sizes, the biggest study being that of Kay et al. (1955) with 175 subjects. Seven studies examined inpatients exclusively and the length of follow-up ranged from 6 to 104 months (mean 31.9 months). When the studies were analysed as a group, the shorter fol- low-ups (less than 24 months) found 43.7 per cent of patients to have been well throughout, 15.8 per cent to have relapsed and then recovered, 27 per cent to have been continuously ill, and 13.2 per cent had been assigned to other outcome categories such as relapse without further recovery, death,

emerging dementia or lost to follow-up. The follow- ups of 24 months and longer yielded figures of 27.4 per cent, 34.2 per cent, 9.9 per cent and 28.5 per cent respectively. Factors modifying prognosis were assessed in eight studies. Cognitive impair- ment and physical illness were usually associated with poor outcome, but the age of onset of the first depressive episode and the age of the patient at presentation had an inconsistent effect across studies. Although severity of symptoms was asso- ciated with poor prognosis in four studies, it is notable that the two studies of outpatients alone (Cole, 1985; Magni et al., 1988) and the one that included both inpatients and outpatients (Murphy, 1983) had poorer outcomes than the group as a whole; and the one study which found depressive delusions to indicate a poor prognosis had a very low rate for the administration of electroconvulsive therapy (Murphy, 1983). No study found marital status or living circumstances to be related to out- come, but severe intervening life events were related to poor outcome and property ownership to good outcome in Murphy’s study (1983). Post (1972) found that regular visits by a social worker offered no protection against relapse.

Since the publication of Cole’s review, another study has appeared (Burvill et al., 1991) describing the one year outcome of 103 patients aged 60 and over, presenting to psychiatrists and diagnosed as having Major Depressive disorder (American Psy- chiatric Association, 1980). The great majority of these Western Australian subjects were inpatients, all were examined with a structured interview and assessed for physical illness, cognitive impairment, adverse life events and personality. Despite the care with which the study was conducted it had similar failings to most others in the lack of formation of an appropriate inception cohort, inadequate description of referral pattern, and apparent lack of blind outcome assessment, though in addition to Murphy’s outcome criteria it introduced a poten- tially valuable second outcome classification with reasonably clear criteria for allocating patients to either good or bad outcome groups. The results were similar to those for the studies of less than 24 months duration reviewed by Cole: 47 per cent were well at one year, 18 per cent relapsed and recovered, 24 per cent were depressive invalids or continuously ill, while 11 per cent died, though by the dichotomous outcome criteria developed by the authors only 32 per cent had an unequivocal good outcome. Severe life events in the three months prior to admission were associated with good one-

THE PROGNOSIS OF DEPRESSION 479

year prognosis, but the authors highlight the fact that because of its sample size the study lacked the statistical power to reject the null hypothesis in respect of a host of other variables examined to determine whether they had any effect on prog- nosis.

A second study of note which is yet to appear in print was presented at a meeting of the Royal College of Psychiatrists in July 1990. Meats and Jolley (1 990) addressed the important question of whether depression in late life has a different pro- gnosis from that occurring earlier. They found that 56 elderly depressed inpatients were more likely to be well after a year than 24 younger depressed patients treated in the same unit (68 per cent vs 50 per cent well), and were one third as likely to be classed as having a poor outcome (16 per cent vs 46 per cent), but twice as many of the older patients were dead at follow-up (16 per cent vs 8 per cent). Despite the small size of the sample, this study highlights an interesting area of comparative research which has received little attention to date.

It is likely that depressed subjects detected in community surveys are different in many respects from the smaller number who consult clinicians for help (Costello, 1990). Kivela et al. (1988) screened persons aged over 60 in a Finnish community with the Zung Depression Scale (1965), then interviewed all high scorers and a random subsample of low scorers with a semi-structured interview. They found that 264 suffered from a DSM-I11 affective disorder (26.8 per cent prevalence rate) which in over three quarters of subjects was classed as Dys- thymia (American Psychiatric Association, 1980). At follow-up, over one year later, 5 cases were lost, 29 were dead, and 13 demented; 109 had good reco- very, but 108 had relapsed or had been conti- nuously ill until follow-up (Kivela et al., 1991). Forty per cent of patients with dysthymic disorder were well at follow-up compared with forty-five per cent of patients who had initially been diag- nosed as having major depression. Treatment fac- tors were not examined in relation to outcome, but neither age nor sex had any effect. Some social fac- tors, and self-rated poor health were associated with poor outcome, but a lack of published confi- dence limits, and the large matrix of variables exa- mined in relation to outcome, make further interpretation of this study difficult. Davidson et al. (1988) reported that depression was significantly associated with mortality at three years in a sample of 1070 elderly Liverpudlians examined with the GMSIAGECAT package (Copeland et al., 1987a),

though the effect was far weaker for depression than that found for organic psychosis. ‘Diagnostic case level’ depressive illness affected 11.5 per cent of the Liverpool sample at index interview. Only 4 per cent of these subjects were receiving antide- pressant drugs, and after three years only one third showed evidence of recovery while one in twenty had developed an organic psychosis (Dewey, per- sonal communication, 1991). Fredman et al., (1989) failed to find an association between depression and two year mortality risk among 1606 elderly participants at one of the Epidemiologic Catch- ment Area study sites, but given the severe metho- dologic deficiencies of that epidemiological undertaking (Burvill, 1987; Snowdon, 1990) per- haps not too much should be made of this result which flies in the face of most other published work on mortality in late life depression (e.g. Murphy et al., 1988).

Despite the methodological imperfections of studies published to date, some tentative conclu- sions may be inferred regarding the prognosis of depression in old age when treated in a psychiatric inpatient facility. Studies of outpatient and com- munity populations are too few or flawed to permit much in the way of inference, though the hypothesis that less severe disorder will be more likely to recover completely than the more serious variety requiring hospital admission (Burvill et al., 1986) is as yet unconfirmed by published work. Most old patients treated for depression in hospital seem to get better, but a sizeable minority fail to recover, or continue to be disabled, despite some improve- ment. As time passes, relapse becomes commoner, consistent with Rennie’s long standing observation (1942) that only 15 per cent of patients of all ages admitted to hospital with depression failed to have a further episode of illness within 20-28 years. The consensus of published work suggests that depres- sion raises the risk of death, and this increased risk may not completely be explained by a higher rate of physical illness among the depressed elderly (Murphy et al., 1988). Specific physical correlates such as cerebral ventricular enlargement may be associated with excess mortality (Jacoby et al., 1981) and require further evaluation. Dementia does not seem to supervene any more frequently in depressed than in non-depressed old people, but the small proportion with depressive pseudode- mentia may have an increased long-term risk of cognitive decline (Kral, 1983; Alexopoulos, 1989). Physical illness also appears to be associated with poor outcome, but evidence regarding sex, age at

480 D. AMES AND N. ALLEN

presentation, age at onset of first depression, type of depression, depression severity, most social factors and treatment variables is too confused or rests on too few studies to allow reliable inference. The most useful immediate lesson from published studies has been applied by many old age psychi- atrists already: elderly depressed patients have a high risk of non-recovery and if they do recover subsequent relapse becomes increasingly likely with the passage of time. Until evidence to the contrary is presented it would seem prudent to pursue ener- getic treatment of index episodes of depression in old age, to review patients frequently, to be liberal in the dispensation of prophylactic medication, and to treat relapses early and aggressively.

If the preceding sentence reads a little like a state- ment in favour of motherhood and apple pie, it should not be interpreted as any cause for com- placency. In the competitive world of health provi- sion there is an imperative need for health providers to demonstrate that what they purport to do is actually of benefit to those who receive their wares. If old age psychiatry is to justify a maintained or increased share of existing health resources it must demonstrate unequivocally that treating depression in the old conveys benefits that can be understood even by health economists. There is a clear need for well designed prognostic studies of depression in elderly subjects. These should be conducted among inpatients and outpatients treated by psy- chiatrists, those presenting to primary care, and those discovered by community surveys. Such stu- dies should take account of the McMaster Univer- sity recommendations reiterated by Cole, and should aim to study samples in excess of 200 so as to prevent a lack of validity due to the statistical imprecision conferred by small sample size (Burvill et al., 1991). Britain with its unified system of health care and low rate of private psychiatric practice looms as an ideal venue for such work, but because environmental, social, cultural and genetic factors may influence outcome, there is a need for comple- mentary studies in different countries. It would be best if future studies employed structured inter- views and operational diagnostic and outcome cri- teria which are internationally recognized and will allow direct comparison between studies. Diag- noses should be made using more than one diagnos- tic system simultaneously in order to minimize the theoretical biases inherent in individual systems (McGorry et al., 1989). Published material should contain sufficient data to permit inclusion in later meta-analyses. Prognostic studies should be

regarded as an important preliminary to the much needed investigation of the effect of randomly assigned treatment packages upon the immediate and long term outcome of depression in old age. All psychiatrists involved in providing services to the elderly should consider what contribution they can make to the advancement of knowledge in this key area of practice.

ACKNOWLEDGEMENTS

Eleanor Flynn and Tim Layton offered helpful comments on drafts of the manuscript, and Yvonne Liddicoat provided invaluable secretarial assist- ance.

REFERENCES

Alexopoulous, G. S. (1989) Late-life depression and neurological brain disease. Int. J. Geriat. Psychiat. 4, 187-190.

American Psychiatric Association. (1980) Diagnostic and Statistical Manual of Mental Disorders 3rd ed. Ameri- can Psychiatric Association, Washington, DC.

Baldwin, R. and Jolley, D. (1986) The prognosis of depression in old age. Brit. J. Psychiat. 149,574583.

Burvill, P. W., Stampfer, H. and Hall, W. (1986). Does depressive illness in the elderly have a poor prognosis. Aust. N. Z . J. Psychiatry 20,422-427.

Burvill, P. W. (1987) An appraisal of the NIMH Epide- miologic Catchment Area Program. Aust. N.Z. J. Psy- chiatry 21, 175-184.

Burvill, P. W., Hall, W. D., Stampfer, H. G. and Emmer- son, J. P. (1991) The prognosis of depression in old age? Brit. J. Psychiat. 158,6471.

Cole, M. (1985) The course of elderly depressed out- patients. Can. J. Psychiatry, 30,217-220.

Cole, M. (1990) The prognosis of depression in the elderly. Can. Med. Assoc. J. 143,633-639.

Copeland, J. R. M., Dewey, M., Wood, N., Searle, R., Davidson, I. and McWilliam, C. (1987a) Range of mental illness among the elderly in the community: prevalence in Liverpool using the GMS-AGECAT package. Brit. J. Psychiat. 150,815-823.

Copeland, J. R. M., Gurland, B. J., Dewey, M. E., Kel- leher, M. J., Smith, A. M. R. and Davidson, I. A. (1987b) The distribution of dementia, depression and neurosis in elderly men and women in an urban com- munity: assessed using the GMS-AGECAT package. Int. J. Geriat. Psychiat. 2, 177-1 84.

Costello, C. G. (1990) The similarities and dissimilarities between community and clinic cases of depression. Brit. J. Psychiat. 157, 812-821.

THE PROGNOSIS OF DEPRESSION 48 1

Davidson, I. A., Dewey, M. E. and Copeland, J. R. M. (1988) The relationship between mortality and mental disorder: evidence from the Liverpool longitudinal study. Znt. J. Geriat. Psychiat. 3,95-98.

Department of Clinical Epidemiology and Biostatistics, McMaster University Health Sciences Centre. (1981) How to read clinical journals: 3. To learn the clinical course and prognosis of disease. Can. Med Assoc. J.

Fredman, L., Schoenbach, V. J., Kaplan, B. H. et al. (1989) The association between depressive symptoms and mortality among older participants in the Epide- miologic Catchment Area-Piedmont Health Survey. J. Gerontol. 44, S149-S156.

Hoch, A. and MacCurdey, J. (1922) The prognosis of involutional melancholia. Arch. Neurol. Psychiatry 7 , 1-37.

Jacoby, R., Levy, R. and Bird, J. (1981) Computed tomo- graphy and outcome of affective disorder: a follow-up study of elderly patients. Brit. J. Psychiat. 139, 288- 292.

Kay, D., Roth, M. and Hopkins, B. (1955) Affective disorders in the senium: their association with organic cerebral degeneration. J. Ment. Sci. 101, 302-316.

Kivela, S.-L., Pahkala, K. and Laippala, P. (1988) Preva- lence of depression in an elderly population in Finland. Acta Psychiatrica Scand. 78,401-413.

Kivela, S.-L., Pahkala, K. and Laippala, P. (1991). A one-year prognosis of dysthymic disorder and major depression in old age. Znt. J. Geriat. Psychiat. 6,

Kral, V. (1983) The relationship between senile dementia (Alzheimer type) and depression. Can. J. Psychiatry 28,304-306.

Livingstone, G., Hawkins, A., Graham, N., Blizard,

124,869-872.

81-87.

B. and Mann, A. (1990) The Gospel Oak Study: preva- lence rates of dementia, depression and activity limit- ation among elderly residents in inner London. Psychol. Med. 20,137-146.

Magni, G., Palazzolo, 0. and Bianchin, G. (1988) The course of depression in elderly outpatients. Can. J. Psychiatry 33,21-24.

McGorry, P., Copolov, D. L. and Singh, B. (1989) The validity of the assessment of psychopathology in the psychoses. Aust. N. Z. J. Psychiatry, 4,469482.

Meats, P. and Jolley, D. (1990) Prognosis of depression in the elderly [abstract] In: The Royal College of Psy- chiatrists Annual Meeting 1990, Abstracts, 34-35.

Murphy, E. (1983) The prognosis of depression in old age. Brit. J. Psychiat. 142, 1 11-1 19.

Murphy, E., Smith, R., Lindesay, J. and Slattery, J. (1988) Increased mortality rates in late-life depression. Brit. J. Psychiat. 152,347-353.

Post, F. (1972) The management and nature of depressive illness in late life: a follow through study. Brit. J. Psy- chiat. 112,393404.

Post, F. (1982) Functional disorders: I. Description, inci- dence and recognition. In: The Psychiatry of Late Life (R. Levy and F. Post Eds) Blackwell Scientific, Oxford.

Rennie, T. (1942) Prognosis in manic-depressive psy- choses. Am. J. Psychiatry 98,801-814.

Roth, M. (1955) The natural history of mental disorders in old age. J. Ment. Sci. 101,281-301.

Schwartz, S. and Griffi, T. (1986) Medical Thinking: The Psychology of Medical Judgement and Decision Making, Springer-Verlag, New York.

Snowdon, J. (1990) The prevalence of depression in old age. Znt. J. Geriat. Psychiat. 5 , 141-144.

Zung, W. (1965) A self rating depression scale. Arch. Gen. Psychiatry 12,65-70.