Schizophrenia
Research,
3 (1990)
241-25
241
1
Elsevier
SRS 00110
A depression Donald 1University of Calgary, Cross Hospital,
Addington’,
Department
2210 2nd Street
of Psychiatry,
S. W., Calgary,
rating scale for schizophrenics Jean Addington Foothills
Hospital,
and Bernard
Schisse13
1403 29th St. N. W., Calgary, N. W. T2N 2T9, Canada,
AB T2S IS6, Canada, and 3Department Saskatoon, Saskatchewan, Canada
of Sociology,
University
=Holy
of Saskatchewan,
Scales for assessing depression are well developed for non-psychotic populations but have been criticized for being inappropriate for psychotic populations. As a result we have developed a new rating scale for the measurement of depression in schizophrenia based on items selected from the Hamilton Depression Rating Scale and the Present State Examination. The selection was based on a three stage procedure first factor analysis then measures of internal consistency and finally face validity. Ratings of depression were made on 50 acutely ill schizophrenics meeting DSM-III criteria for schizophrenia assessed at two points in time. Our results indicate that several items from both scales form a superior instrument for measuring depression in schizophrenia. The eleven items generated a Cronbach’s alpha of 0.84 at time one and 0.89 at time 2. Key waords: Depression;
(Schizophrenia)
INTRODUCTION
The increasing attention paid to the negative symptoms of schizophrenia in the last decade has brought about the development of a number of negative symptom rating scales (Andreasen, 1982; Lewine et al., 1983; Heinrichs et al., 1984; Iager et al., 1985; Kay et al., 1987). During the same period there has been increasing attention given to depression in schizophrenia because of its significance for diagnosis, treatment and outcome (McGlashan and Carpenter 1976; Knights et al., 1981; Hirsch, 1982; Mandel et al., 1982; Johnson, 1986; Bland, there are a 1987; Siris et al., 1987). However number of difficulties associated with the assessment of depression in schizophrenia. These include the temporal variability of depressive syndromes (Knights et al., 1979; Siris et al., 1984, 1986; Craig et al., 1985) the poor correlation between selfreport and observer reports of depression (Craig Correspondence to: D. Addington, University of Calgary, Department of Psychiatry, Foothills Hospital, 1403 29th St, N.W., Calgary, N.W. T2N 2T9, Canada.
0920-9964/90/$03.50
G 1990 Elsevier
Science Publishers
and Van Natta, 1976; Brown et al., 1979), and the possible overlap with extrapyramidal syndromes (Rifkin et al., 1975; Van Putten and May, 1978) and negative symptoms (Prosser et al., 1987). The full range of depression rating scales used to assess depression in non-psychotic populations has been used in studies of depression in schizophrenia. Despite the finding that patterns of depression in outpatient schizophrenics resemble those in other depressed groups (Weissman et al., 1977) comparisons of different rating scales on the same patients suggest that these scales may measure different dimensions in schizophrenic patients than they do in patients with affective disorders (Craig et al., 1985; Addington and Addington, 1989). Finally different measures of depression appear to be more congruent in the post-psychotic phase of the disorder than in the acute phase of the disorder (Addington and Addington, 1989). The present study was undertaken to derive a new rating scale for depression in schizophrenics which would be useful for assessing levels of depression in this population. The internal reliability of the scale is compared to two existing scales at two stages of the disorder.
B.V. (Biomedical
Division)
248
METHOD
The Hamilton depression rating scale (HDRS) (Hamilton, 1960) and a scale derived from the four depressive syndromes of the Present State Examination (PSE) (Wing et al., 1974) were used to rate a sample of schizophrenics, first, during an acute relapse and again, at six month follow up. Interrater reliability was established by the principal investigator (PI) for the PSE on a separate series of videotaped interviews at the Clinical Research Center at UCLA. Interrater reliability between the PI and research center staff for individual PSE items was 83%. Interrater reliability for the HDRS was established locally by an observer rating interviews done by the PI, interrater reliability was 82%. Subjects were diagnosed according to DSM-III criteria (APA, 1980). Diagnosis was made on the basis of data combined from interviews with a modified form of the PSE (Wing et al., 1974), chart review, and family interview. Patients were all competent to give informed consent and were all receiving antipsychotic medication. Subjects were excluded if they had any of the following: (a) evidence of an organic central nervous system disorder; (b) significant or habitual drug or alcohol abuse in the past year; (c) mental retardation. The following three steps were used in scale construction in the following order: (1) factor analysis was used to select items from the HDRS and PSE(D) which explained, at each of the two points in time, the greatest proportions of variance in the rating of depression: thereby ensuring all items discriminated between schizophrenics who were and were not depressed. (2) Cronbach’s alpha was calculated to assess the internal consistency of the items selected at both points in time. (3) Selected items were assessed for face validity. The internal consistency of the newly constructed scale was compared to that of the HDRS and PSE(D) at both points in time.
admission units in a general teaching hospital who were competent and willing to give informed consent. The mean age of the sample was 30.9 years. The mean time since first hospitalization was 8.3 years, mean number of admissions 5.2, and mean age at first admission 22.4 years. A total of 50 subjects entered the study and 41 were successfully assessed at 6 month follow up.
RESULTS
Comparisons between subjects symptom ratings at time 1 and time 2 are presented in Table 1 indicating a significant decline in positive and negative symptoms but a less clear cut decline in depressive symptoms. Results for the second factor analysis are presented in Table 2. Hamilton depression scale items are underlined and the items common at time 1 and time 2 are marked with an asterisk. The results in Table 2 indicate strong factor loadings on factor 1 at time 1 and time 2. The percent of variation explained by factor 1 is quite strong at both times (60% and 86.3% respectively). As well, consistently strong factor score coefficients on factor 1 indicate that the selected items reliably measure one common underlying factor of depression. This conclusion is further tested by subjecting the items at time 1 and time 2 to an analysis of their internal consistency. Results for this analysis are presented in Table 3. Findings from the factor analysis are corroborated. Only one item at time 1 and time 2 dimin-
TABLE
1
Sympiom comparisonS time I vs. time 2
SAMPLE
Negative symptoms Positive symptoms Hamilton (HDRS) PSE (D)
The sample consisted of 50 consecutive voluntary admissions with schizophrenia to two psychiatric
*P
Research,
3 (1990)
241-25
241
1
Elsevier
SRS 00110
A depression Donald 1University of Calgary, Cross Hospital,
Addington’,
Department
2210 2nd Street
of Psychiatry,
S. W., Calgary,
rating scale for schizophrenics Jean Addington Foothills
Hospital,
and Bernard
Schisse13
1403 29th St. N. W., Calgary, N. W. T2N 2T9, Canada,
AB T2S IS6, Canada, and 3Department Saskatoon, Saskatchewan, Canada
of Sociology,
University
=Holy
of Saskatchewan,
Scales for assessing depression are well developed for non-psychotic populations but have been criticized for being inappropriate for psychotic populations. As a result we have developed a new rating scale for the measurement of depression in schizophrenia based on items selected from the Hamilton Depression Rating Scale and the Present State Examination. The selection was based on a three stage procedure first factor analysis then measures of internal consistency and finally face validity. Ratings of depression were made on 50 acutely ill schizophrenics meeting DSM-III criteria for schizophrenia assessed at two points in time. Our results indicate that several items from both scales form a superior instrument for measuring depression in schizophrenia. The eleven items generated a Cronbach’s alpha of 0.84 at time one and 0.89 at time 2. Key waords: Depression;
(Schizophrenia)
INTRODUCTION
The increasing attention paid to the negative symptoms of schizophrenia in the last decade has brought about the development of a number of negative symptom rating scales (Andreasen, 1982; Lewine et al., 1983; Heinrichs et al., 1984; Iager et al., 1985; Kay et al., 1987). During the same period there has been increasing attention given to depression in schizophrenia because of its significance for diagnosis, treatment and outcome (McGlashan and Carpenter 1976; Knights et al., 1981; Hirsch, 1982; Mandel et al., 1982; Johnson, 1986; Bland, there are a 1987; Siris et al., 1987). However number of difficulties associated with the assessment of depression in schizophrenia. These include the temporal variability of depressive syndromes (Knights et al., 1979; Siris et al., 1984, 1986; Craig et al., 1985) the poor correlation between selfreport and observer reports of depression (Craig Correspondence to: D. Addington, University of Calgary, Department of Psychiatry, Foothills Hospital, 1403 29th St, N.W., Calgary, N.W. T2N 2T9, Canada.
0920-9964/90/$03.50
G 1990 Elsevier
Science Publishers
and Van Natta, 1976; Brown et al., 1979), and the possible overlap with extrapyramidal syndromes (Rifkin et al., 1975; Van Putten and May, 1978) and negative symptoms (Prosser et al., 1987). The full range of depression rating scales used to assess depression in non-psychotic populations has been used in studies of depression in schizophrenia. Despite the finding that patterns of depression in outpatient schizophrenics resemble those in other depressed groups (Weissman et al., 1977) comparisons of different rating scales on the same patients suggest that these scales may measure different dimensions in schizophrenic patients than they do in patients with affective disorders (Craig et al., 1985; Addington and Addington, 1989). Finally different measures of depression appear to be more congruent in the post-psychotic phase of the disorder than in the acute phase of the disorder (Addington and Addington, 1989). The present study was undertaken to derive a new rating scale for depression in schizophrenics which would be useful for assessing levels of depression in this population. The internal reliability of the scale is compared to two existing scales at two stages of the disorder.
B.V. (Biomedical
Division)
248
METHOD
The Hamilton depression rating scale (HDRS) (Hamilton, 1960) and a scale derived from the four depressive syndromes of the Present State Examination (PSE) (Wing et al., 1974) were used to rate a sample of schizophrenics, first, during an acute relapse and again, at six month follow up. Interrater reliability was established by the principal investigator (PI) for the PSE on a separate series of videotaped interviews at the Clinical Research Center at UCLA. Interrater reliability between the PI and research center staff for individual PSE items was 83%. Interrater reliability for the HDRS was established locally by an observer rating interviews done by the PI, interrater reliability was 82%. Subjects were diagnosed according to DSM-III criteria (APA, 1980). Diagnosis was made on the basis of data combined from interviews with a modified form of the PSE (Wing et al., 1974), chart review, and family interview. Patients were all competent to give informed consent and were all receiving antipsychotic medication. Subjects were excluded if they had any of the following: (a) evidence of an organic central nervous system disorder; (b) significant or habitual drug or alcohol abuse in the past year; (c) mental retardation. The following three steps were used in scale construction in the following order: (1) factor analysis was used to select items from the HDRS and PSE(D) which explained, at each of the two points in time, the greatest proportions of variance in the rating of depression: thereby ensuring all items discriminated between schizophrenics who were and were not depressed. (2) Cronbach’s alpha was calculated to assess the internal consistency of the items selected at both points in time. (3) Selected items were assessed for face validity. The internal consistency of the newly constructed scale was compared to that of the HDRS and PSE(D) at both points in time.
admission units in a general teaching hospital who were competent and willing to give informed consent. The mean age of the sample was 30.9 years. The mean time since first hospitalization was 8.3 years, mean number of admissions 5.2, and mean age at first admission 22.4 years. A total of 50 subjects entered the study and 41 were successfully assessed at 6 month follow up.
RESULTS
Comparisons between subjects symptom ratings at time 1 and time 2 are presented in Table 1 indicating a significant decline in positive and negative symptoms but a less clear cut decline in depressive symptoms. Results for the second factor analysis are presented in Table 2. Hamilton depression scale items are underlined and the items common at time 1 and time 2 are marked with an asterisk. The results in Table 2 indicate strong factor loadings on factor 1 at time 1 and time 2. The percent of variation explained by factor 1 is quite strong at both times (60% and 86.3% respectively). As well, consistently strong factor score coefficients on factor 1 indicate that the selected items reliably measure one common underlying factor of depression. This conclusion is further tested by subjecting the items at time 1 and time 2 to an analysis of their internal consistency. Results for this analysis are presented in Table 3. Findings from the factor analysis are corroborated. Only one item at time 1 and time 2 dimin-
TABLE
1
Sympiom comparisonS time I vs. time 2
SAMPLE
Negative symptoms Positive symptoms Hamilton (HDRS) PSE (D)
The sample consisted of 50 consecutive voluntary admissions with schizophrenia to two psychiatric
*P
