DEPRESSION IN DEMENTIA SUFFERERS

In terms o f the characteristics o f this sample, they would appear to be comparable to the community sample o f dementia sufferers in OrrelTs (1994) study o f life events and dementia in terms o f age and gender. The finding that 40.9% o f the sample o f dementia sufferers were depressed is slightly higher than that reported in other studies where the average rate of prevalence is around 30% (Teri & Wagner, 1992, Ballard et al, 1993) although rates of 40-50% have been reported (Vida et al, 1993). In addition, Orrell (1995a) reported depressive symptoms in 20% o f dementia patients and in 26% o f community dementia controls. The higher than average prevalence o f depression in this sample may be in part a reflection o f the difference in sample selection and measures o f depression used. Ballard et al (1996) reported a higher prevalence o f depression among samples in contact with clinical services than in community samples. Given that the sample in this study were recruited from day centres and outpatient services, this may

Chapt^ Four: Discussion

DSM IV criteria or research diagnostic criteria for major depression. The Cornell scale is primarily used as a measure o f depressive symptomatology and not as a diagnostic tool. Therefore, the rates o f depression in this sample as measured by the Cornell may include some people who would not meet the criteria for clinical depression. However, standard criteria which relies on interview methods may miss depression in the severe dementia group.

The finding that severity o f dementia was unrelated to depression is in keeping with other studies (Fitz & Teri, 1994, Haupt et al, 1995) as is the lack o f association between age and gender and depressive symptoms (Ballard et al, 1996). In this study, rates o f depression were not related to diagnosis. The rate of depression in Alzheimer’s Disease (AD) was 40% and in Multi Infarct Dementia (MID) 40.9%. However, other studies have reported a much higher prevalence in patients with AD than MID (Cummings et al, 19S7). The fact that different diagnostic criteria were used might have important implications in this respect, e.g. persons with MID are more likely to have problems with expression and comprehension o f language and so self report may underrate symptoms.

Life events and depression in dementia

This study found a significant relationship between life events and depression in dementia sufferers. The proportion o f this sample reporting at least one severe and independent life event in the 6 months prior to interview was higher in the depressed

Ctuqpter Four: Discussion

relationship between life events and depression in the elderly (Murphy, 1982, Emmerson et al, 1989). Only those life events which were rated as both severe and independent were included in the analysis and the rate of such life events for the total sample (42.7%) falls between the 48% found by Murphy (1982) and 38% reported by Emmerson et al (1989). In addition, the most frequently reported events were bereavement and ill health which was in keeping with that reported by other studies o f life events in this age group; for example, these events were the most frequently reported in a sample of 188 persons over 65 (Linn, 1980).

The finding o f a significant association between life events and depression in dementia sufferers replicates the findings o f Orrell & Bebbington (1995c), Their study reported a consistent excess of severe and threatening life events in those dementia sufferers with depressive symptoms. In this study, a significant association between life events and depressive symptoms was found for the 0-6 month period, but more specifically, for the 3 months prior to interview. During this period, 61.5% of the depressed group reported at least one life event compared to 38.5% o f the non depressed group. The significance o f 0-3 months has been reported in the work o f Brown & Harris (1978) and Emmerson (1989). However, the rate of life events in this time period is far greater than that reported in either of these studies (42%) and (24%) respectively or the 40% found in dementia sufferers with depression (Orrell & Bebbington, 1995a). In contrast to this study, Orrell & Bebbington (1995c) found a significant association between life events

Chapter Four: Discusâoa

even suggested that events occurring 2-7 months before intervie^v are less strongly associated with depression than those 8-13 months beforehand (Tennant, 1979),

One possible explanation for this difference may relate to the smaller number o f life events occurring in the 4-6 months prior to interview in this sample. It is conceivable that taken together the impact o f life events on depression may span a 6 month period and thus it is not clear where the major effect lies.

Furthermore, it would appear that the occurrence o f only one severe and independent life event is associated with depression in this sample. This study did not find a cumulative effect o f life events since a comparison o f the number of life events with total depression score did not yield any associations. Similar conclusions were drawn by Brown & Harris with a younger sample (1978) although it is contrast with that reported by Linn (1980) who reported a cumulative effect o f stressful life events.