SF 36 health survey questionnaire: I. Reliability in two patient based studies.

OBJECTIVE--To assess the reliability of the SF 36 health survey questionnaire in two patient populations. DESIGN--Postal questionnaire followed up, if necessary, by two reminders at two week intervals. Retest questionnaires were administered postally at two weeks in the first study and at one week in the second study. SETTING--Outpatient clinics and four training general practices in Grampian region in the north east of Scotland (study 1); a gastroenterology outpatient clinic in Aberdeen Royal Hospitals Trust (study 2). PATIENTS--1787 patients presenting with one of four conditions: low back pain, menorrhagia, suspected peptic ulcer, and varicose veins and identified between March and June 1991 (study 1) and 573 patients attending a gastroenterology clinic in April 1993. MAIN MEASURES--Assessment of internal consistency reliability with Cronbach's alpha coefficient and of test-retest reliability with the Pearson correlation coefficient and confidence interval analysis. RESULTS--In study 1, 1317 of 1746 (75.4%) correctly identified patients entered the study and in study 2, 549 of 573 (95.8%). Both methods of assessing reliability produced similar results for most of the SF 36 scales. The most conservative estimates of reliability gave 95% confidence intervals for an individual patient's score difference ranging from -19 to 19 for the scales measuring physical functioning and general health perceptions, to -65.7 to 65.7 for the scale measuring role limitations attributable to emotional problems. In a controlled clinical trial with sample sizes of 65 patients in each group, statistically significant differences of 20 points can be detected on all eight SF 36 scales. CONCLUSIONS--All eight scales of the SF 36 questionnaire show high reliability when used to monitor health in groups of patients, and at least four scales possess adequate reliability for use in managing individual patients. Further studies are required to test the feasibility of implementing the SF 36 and other outcome measures in routine clinical practice within the health service.     

"Specific" scale compared with "generic" scale: a double measurement of the quality of life in a French community sample of obese subjects

STUDY OBJECTIVE: To determine the aspects of quality of life that are affected by weight in the general population, to develop a specific questionnaire (OSQOL) that can measure with reliability and validity the impact of overweight and obesity on well being, and to compare the results with those obtained using a well known generic tool (the "SF 36" scale). DESIGN: Cross sectional survey with matched control group. SETTING: Community. PATIENTS: A permanent survey base of approximately 10,000 representative ordinary households were screened for weight and height. Five hundred subjects were randomly drawn from the sub-sample of adult people with a body mass index equal or greater than 27. A control sample of 500 subjects matched for sex, age, and employment status was drawn from the non-obese population. MAIN RESULTS: A short specific Quality Of Life scale, the OSQOL, was produced that comprises 11 items belonging to four independent dimensions. Using this scale and the SF36, it was found that: (1) moderately obese subjects (27 < or = BMI < 30) did not significantly differ from the control group except for physical capacity; (2) in the group of obese subjects with a BMI > 30, quality of life seemed to be impaired for five of nine dimensions of the SF36 compared with the control population, all related to physical consequences of obesity. This population essentially perceived itself in terms of poor general health. (3) No significant difference was observed between the samples for the psychological and social dimensions of the SF36. CONCLUSION: The quality of life of patients with severe obesity is impaired, but it mainly affects the physical consequences of the disease. The psychological and social repercussions that could have been expected to affect this population were not demonstrated. The hypothesis of a process of adaptation of the person and their social environment cannot therefore be excluded. Methodologically, comparison of the specific OSQOL with the generic SF3 shows clearly that the two kinds of scales correspond to different objectives and should be considered as complementary.       

SF 36 health survey questionnaire: II. Responsiveness to changes in health status in four common clinical conditions.

OBJECTIVE--To assess the responsiveness of the SF 36 health survey questionnaire to changes in health status over time for four common clinical conditions. DESIGN--Postal questionnaires at baseline and after one year's follow up, with two reminders at two week intervals if necessary. SETTING--Clinics and four training general practices in Grampian region in the north east of Scotland. PATIENTS--More than 1,700 patients aged 16 to 86 years with one of four conditions: low back pain, menorrhagia, suspected peptic ulcer, and varicose veins; and a random sample of 900 members of the local general population for comparison. MAIN MEASURES--A transition question measuring change in health and the eight scales of the SF 36 health survey questionnaire; standardised response means (mean change in score for a scale divided by the standard deviation of the change in scores) used to quantify the instrument's responsiveness to changes in perceived health status, and comparison of patient scores at baseline and follow up with those of the general population. RESULTS--The response rate exceeded 75% in a patient population. Changes across the SF 36 questionnaire were associated with self reported changes in health, as measured by the transition question. The questionnaire showed significant improvements in health status for all four clinical conditions, whether in referred or non-referred patients. For patients with suspected peptic ulcer and varicose veins the SF 36 profiles at one year approximate to the general population. CONCLUSIONS--These results provide the first evidence of the responsiveness of the SF 36 questionnaire to changes in perceived health status in a patient population in the United Kingdom.     

Reliability and validity of the SF-36 in HIV-infected homeless and marginally housed individuals

Objective: To assess the reliability and validity of the Short-Form 36 (SF-36) health survey as a health status indicator among HIV-infected homeless and marginally housed (HMH) individuals. Methods: Between July 1996 and May 2000, a sample of HMH individuals completed interviews that included the SF-36. Responses to the SF-36 were analyzed for missing data, range, internal consistency, and construct validity. Results: Among 330 individuals interviewed, 83% were male, 43% were African-American, and the median age was 39 years. All internal consistency reliability coefficients exceeded 0.70, all item–scale correlations exceeded 0.40, all items were more strongly correlated with their hypothesized scale than any other scale, and all reliability coefficients exceeded inter-scale correlations for the same scale. Three of four physical health scales were significantly associated with CD4 cell count and HIV viral load. All scales were significantly associated with depression. Discussion: We found that scales were internally consistent, items correlated to an acceptable degree with their hypothesized scales, items were distinct from other scales, physical scales were associated with CD4 cell count and viral load, and all scales were associated with depression. These analyses provide evidence for the reliability and validity of the SF-36 as a measure of health status in HIV-positive HMH individuals.     

The development and validation of a short measure of functioning and well being for individuals with Parkinson's disease

Parkinson's disease is a common degenerative neurological condition. A number of general health status measures exist but these may not address areas salient to specific diseases. We report here the development and validation of a short 39 item health status questionnaire for use in Parkinson's disease. Questionnaire items, generated from indepth interviews with people with Parkinson's disease, were developed into a 65 item questionnaire. Data from a postal survey using the 65 item questionnaire were statistically analysed to produce a shorter questionnaire with 39 items and eight scales addressing different dimensions of Parkinson's disease. A second postal survey was conducted in order to assess the reliability and validity of the new 39 item questionnaire. The final questionnaire, referred to here as the 39 item Parkinson's Disease Questionnaire (PDQ-39), proved to have satisfactory internal and test-retest reliability, and construct validity in relation to other measures, reported by respondents with Parkinson's disease.     

Application of the general health status questionnaire SF36 to patients with gastrointestinal dysfunction: initial validation and validation as a measure of change

OBJECTIVE: To determine whether the Short Form (SF36) Health Status Survey is a valid measure of health status and health change for patients with irritable bowel syndrome (IBS). METHODS: The SF36 was self-administered by 116 patients with IBS at the commencement and end of a controlled clinical trial. Patients were recruited through two Sydney teaching hospitals and through private gastroenterologists during 1997 and treated with Chinese herbal medicine. RESULTS: The SF36 health concepts demonstrated internal consistency, construct validity and concurrent validity when applied to patients with significant bowel dysfunction. Patient scores on two health scales of the SF36 (bodily pain, general health) correlated significantly with the bowel symptom scores recorded by patients and gastroenterologists at the beginning and end of the trial period. Actively treated patients significantly improved their scores in four out of eight of the health scales of the SF36 and reported overall improvement compared with inactively treated patients. CONCLUSIONS: The SF36 is a valid measure of general health status in IBS patients, is sensitive to the presence of IBS, and is adequately sensitive to gastrointestinal change in IBS patients. IMPLICATIONS: While the SF36 general health measure is used by the Australian Bureau of Statistics and widely overseas, until recently no data have been available on the sensitivity of the SF36 to gastrointestinal dysfunction or numerous other disorders. The SF36 is not only sensitive to the presence of IBS, it also provides a useful adjunct to current methods of evaluating treatment outcomes for IBS, and potentially other disorders.     

Menstruation disorders more frequent in women with a history of sexual abuse

OBJECTIVE: To determine the relationship between menstruation disorders and prior sexual abuse. DESIGN: Questionnaire investigation. METHOD: A questionnaire was developed consisting of 50 questions about menstruation disorders, premenstrual syndrome and sexual abuse. The questionnaire was mailed to all female patients aged 12-54 years (n = 1805) of one family practice in Den Helder, the Netherlands. RESULTS: The response rate to the questionnaire was 69% (n = 1254). After excluding women who were postmenopausal, pregnant, without a uterus, or who did not answer the questions on sexual abuse, 947 remained. Of these women, 83 (8.7%) reported having experienced sexual abuse. These women had significantly more dysmenorrhoea, more dysfunctional menstrual bleeding and significantly more menstrual cycle irregularities. CONCLUSION: A statistically significant association was found between menstrual problems and prior sexual abuse. Sexual abuse should be considered in the differential diagnosis and treatment of women who seek medical help for inexplicable menstrual disorders.     

Assessing health status and outcomes in a geriatric day hospital

The study objective was to assess the feasibility and usefulness of recommended outcome measures in older people attending a geriatric day hospital for multidisciplinary assessment and rehabilitation. We used the 'Short Form 36' (SF36) questionnaire which had been proposed as a suitable outcome tool for the elderly, as well as standard assessment scales (eg Barthel index). These were administered by interviewers at the start of day hospital attendance and repeated by postal survey three and six months later. Change in overall health status was rated by the clinical team. The study took place in a geriatric day unit based in a support hospital, specialising in assessment and rehabilitation of older people. Participants were older people referred directly from the community, or following an inpatient day, whose assessment indicated a need for multidisciplinary rehabilitation. Stroke and musculo-skeletal disorders were the commonest underlying conditions. There was a high incidence of non-completion on SF36 questions relating to physical and mental function. Subsequent interviews showed that patients found some questions irrelevant. Floor effects were common. In contrast, the standard scales were invariably fully completed. Compared with local population survey data, respondents had low baseline scores on all SF36 dimensions. Differences over time were probably explained by varying methods of administration. In spite of a clinical perception of improved health status during day hospital attendance, both standard and SF36 scores showed overall deterioration. Two conclusions could be drawn from this study. 1. Measures of physical and mental disability and quality of life gave lower results than expected and continued declining over a six month period, even when the clinical team felt that the patient had improved. 2. Administration of SF36 by an interviewer is essential to obtain meaningful results in older people with poor physical health, which should be interpreted with caution. Goal-specific measures may be more useful in this group of patients.     

Assessment of the SF-36 version 2 in the United Kingdom.

OBJECTIVES: To introduce the UK SF36 Version II (SF36-II), and to (a) gain population norms for the UK SF36-II in a large community sample as well as to explore the instrument's internal consistency reliability and construct validity, and (b) to derive the Physical Component Summary (PCS) and Mental Component Summary (MCS) algorithms for the UK SF36-II. DESIGN: Postal survey using a questionnaire booklet, containing the SF-36-II and questions on demographics and long term illness. SETTING: The sample was drawn from General Practitioner Records held by the Health Authorities for Berkshire, Buckinghamshire, Northamptonshire, and Oxfordshire. SAMPLE: The questionnaire was sent to 13,800 randomly selected subjects between the ages of 18-64 inclusive. OUTCOME MEASURES: Scores for the eight dimensions of the UK SF36-II and the PCS and MCS summary scores. RESULTS: The survey achieved a response rate of 64.4% (n = 8889). Internal consistency of the different dimensions of the questionnaire were found to be high. Normative data for the SF-36 are reported, broken down by age and sex, and social class. Factor analysis of the eight domains produced a two factor solution and provided weights for the UK SF36-II. CONCLUSION: The SF36-II domains were shown to have improved reliability over the previous version of the UK SF36. Furthermore, enhancements to wording and response categories reduces the extent of floor and ceiling effects in the role performance dimensions. These advances are likely to lead to better precision as well as greater responsiveness in longitudinal studies.     

SF-36健康调查量表中文版的研制及其性能测试

目的 研制SF-36健康调查量表中文版并验证量表维度建立及记分假设、信度和效度。方法 采用多阶段混合型等概率抽样法,用SF-36健康调查量表中文版对1000户家庭的居民进行自评量表式调查;参照国际生命质量评价项目的标准程序,进行正式的心理测验学试验。结果 在收回的1985份问卷中,18岁以上的有效问卷1972份,其中应答者1688人(85．6％),1316人回答了所有条目,372人有1个或以上的缺失答案,无应答者中文盲、半文盲占65．5％。等距假设在活力(VT)和精神健康(MH)维度被打破了,按重编码后值计算维度分数;条目集群的分布接近源量表及其他2个中文译本;除了生理功能(PF)、躯体疼痛(BP)、社会功能(SF)维度,其余维度有相似的标准差;除了SF、VT维度,其余6个维度条目维度相关一致;除了SF维度,7个维度集合效度成功率范围为75％～100％,,区分效度成功率范围为87．5％～100％。一致性信度系数除了SF、VT维度,其余6维度变化范围为0．72～0．88,满足群组比较的要求。两周重测信度变化范围为0．66～0．94。因子分析产生了2个主成分,分别代表生理健康和心理健康,解释了56．3％的总方差。结论 为SF-36健康调查量表适用于中国提供了证据,已知群效度试验将为量表效度提供更有意义的证据。     

Reliability and validity of an occupational health history questionnaire.

This study determined the reliability and validity of a self-administered occupational health history questionnaire. Reliability was evaluated using a test-retest study design based on 123 volunteers (56% participation rate) who were administered the questionnaire approximately 1 month apart. Validity and general acceptability was evaluated in a clinical setting through in-depth clinician interviews of 25 patients. The interviews assessed patients' understanding of and sensitivities to questions and degree of adherence to initial responses after discussing questions with clinicians. All but one question related to repetitive motion exposures showed 84% or higher agreement. Clinician interviews of patients indicated that most questions were well understood, although some patients misinterpreted questions regarding pregnancy history, repetitive motion, and immunization history. Overall, our results suggest that the questionnaire is highly reliable, valid, and acceptable to both clinicians and employees.     

Abnormal bleeding patterns associated with menorrhagia in women in the community and in women presenting to primary care

BACKGROUND: There is an assumption that in women with menorrhagia 'excessive menstrual loss in regular cycles is the most common clinical presentation' yet epidemiological studies show irregular cycles and bleeding are common. OBJECTIVES: To test the hypothesis that, in women who present to primary care with menorrhagia, excessive menstrual loss in regular cycles is the most common clinical presentation, and to determine the frequency with which symptoms known to be associated with gynaecological malignancy occur. METHODS: A postal survey of all women aged 18-54 years was used to identify symptoms of vaginal bleeding in an urban general practice with 10 000 registered patients. Follow-up surveys were carried out at 6 and 12 months. Consultation data from general practice held records were gathered from baseline to 18 months. Women who consulted with increased vaginal bleeding during the 18-month study period were separately analysed according to their self-reported symptoms in the questionnaire completed in the 6 months prior to the consultation. RESULTS: At baseline, of the 736 women in the community identified with menorrhagia, 46% had at least one symptom of irregular vaginal bleeding. In the subgroup of 138 women with menorrhagia who consulted primary care with increased vaginal bleeding, the proportion with at least one symptom of irregular vaginal bleeding was 73%. CONCLUSION: In women with heavy menstrual bleeding, excessive menstrual loss in regular cycles is not the most common clinical presentation in primary care. Guidelines on menorrhagia should acknowledge the variety of symptoms that women with heavy menstrual bleeding present to primary care.     

Comparison of WHOQOL-BREF and SF-36 in patients with HIV infection

The purpose of the study was to evaluate the reliability and validity of the two generic instruments, the WHOQOL and the SF-36, for assessing health-related quality of life in 224 patients with HIV infection. The internal consistency ranged from 0.75 to 0.86 across the WHOQOL-BREF domains and from 0.72 to 0.93 across the SF-36 scales. The scores of all WHOQOL-BREF domains and SF-36 scales correlated positively with the measure of happiness, Sat-HRQOL and self-perceived health status, and correlated negatively with the number and intensity of symptoms. Patients with higher CD4 cell counts scored significantly higher on G4 (general health), three WHOQOL-BREF domains, seven SF-36 scales, and PCS (physical component summary). Patients with fewer symptoms and with less intensity of symptoms had significantly higher scores on all four domains of WHOQOL-BREF, eight scales, PCS, and MCS (mental component summary) of the SF-36 scale. The correlations between the physical, psychological, and social domains of the WHOQOL-BREF and PF (physical functioning), MH (mental health), and SF (social functioning) of the SF-36 were 0.51, 0.75, and 0.54, respectively. There is also good correlation between PCS of the SF-36 and the physical domain of the WHOQOL-BREF (r = 0.48), and between MCS and all four domains of the WHOQOL-BREF (r range = 0.60–0.75). The WHOQOL-BREF domains showed fewer floor or ceiling effect than the SF-36 scales. We concluded that both the WHOQOL-BREF and the SF-36 are reliable and valid health related quality-of-life instruments in patients with HIV infection.     

Quality of life and parkinson's disease: Translation and validation of the US Parkinson's Disease Questionnaire (PDQ-39)

Parkinson's disease is a common progressive neurodegenerative disorder affecting an estimated 4 million people worldwide. A number of general health status measures exist but few fully capture the subjective evaluation of life quality associated with Parkinson's disease. We report here the results of: (1) translating the British PDQ-39 into a US version, (2) validity and reliability of the new US PDQ-39 questionnaire, and (3) parallel validation analyses following the method published in the development of the British version of the PDQ-39. Data were collected by postal survey on 150 patients recruited from neurology clinics in the Seattle area. A short, generic health status measure (SF-36) was used to test convergent validity, and a three-day test–retest assessed the reliability of the PDQ-39. The US version of the PDQ-39 demonstrated acceptable internal consistency ( = 0.51 to 0.96) and proved to be reproducible (0.86 to 0.96). Subscales of the PDQ-39 showed convergence with like scales of the SF-36 and was able to discriminate between levels of symptom severity.     

Assessment of patients with menorrhagia: How valid is a structured clinical history as a measure of health status?

A patient-administered questionnaire for menorrhagia based on the type of questions asked when taking a gynaecological history was developed and tested using the following steps: literature reviews, devising the questions, testing responses for internal consistency and test-retest reliability and validating the questionnaire by comparing patient's scores with their responses to the SF-36 general health measure, and with family practitioner perceptions of severity. The main sample consisted of 351 women with menorrhagia, 246 referred to gynaecology ambulatory clinics and 105 from four large training practices in North-east Scotland. Following testing, two questions were discarded from the questionnaire. The final questionnaire demonstrated a good level of reliability and the resulting patient scores correlated significantly with their scores on the scales making up the general health measure. The questions asked in taking a clinical history from a woman with menorrhagia can be used to construct a valid and reliable measure of health status. This clinical measure may be a useful guide in selection for treatment and in the assessment of patient outcome following treatment.This research and the Health Services Research Unit are both funded by the Chief Scientist Office of the Scottish Office Home and Health Department; however the opinions expressed are those of the authors, not the SOHHD.     

Measuring the health of Scottish drug users

Information on how individuals perceive their own health is important for providing appropriate health‐related support and monitoring health over time. The Short Form 36 (SF‐36) Health Status Questionnaire is one of the most widely used generic measures of self‐perceived health status. Despite this, there has been no large‐scale research documenting the SF‐36 scores of problem drug users in the UK. The present paper has two aims: (1) to compare the self‐perceived health of a sample of problem drug users with that of a sample from the general population; and (2) to investigate differences between the self‐perceived health of various subgroups of problem drug users. In total, 1179 individuals starting a new episode of drug misuse treatment in Scotland were invited to complete a structured questionnaire that included the SF‐36. Out of these, 1033 (87.6%) agreed and 990 successfully completed all SF‐36 questions. The 990 completers were more likely than the 43 partial completers to be male [odds ratio (OR) = 0.45; 95% confidence interval (95% CI) = 0.24–0.85] and not in prison (OR = 0.36; 95% CI = 0.19–0.68). The reliability of the SF‐36 – measured by internal consistency – was very good (Cronbach's α > 0.7 for all eight dimensions). Comparing the respondents’ mean dimension scores with those of a sample from the UK general population revealed that the drug users’ health was consistently worse than that of the general population (> 20 points on seven out of the eight scales). Differences between the mean SF‐36 scores of various subcategories of respondents were analysed using t‐tests or an analysis of variance, as appropriate. The factors considered were: sex; age; imprisonment; relationship status; homelessness; and recent drug injection. Significant differences between particular groups of respondents were identified. Despite limitations with the data presented, the paper highlights the utility of the SF36 for drug misuse treatment providers.     

Reliability of questionnaire responses as compared with interview in the elderly: views of the outcome of transurethral resection of the prostate.

Three hundred and eighty-eight men undergoing transurethral resection of the prostate for benign prostatic hypertrophy completed a presurgical questionnaire and three follow-up questionnaires 3, 6 and 12 months after surgery. The questionnaires covered details of prostatic symptoms, general health, and expectations and results of surgery. At each follow-up point 40 randomly selected patients were interviewed by two female research assistants. The response rate to the questionnaires was over 90% at each follow-up point while that for the interviews was lower at around 80%. We examine the reliability of the postal questionnaires in assessing health status by comparing questionnaire and interview responses, with a view to the wider employment of such a method in the follow-up of surgical patients. In general, and as reported elsewhere, responses to questions on easily defined topics are highly comparable between questionnaire and interview. Responses to more subjective questions are moderately reliable, but with a tendency for postal questionnaires to underestimate a patient's health problems. It is difficult to assess the reliability of the questionnaires with regard to questions of an intimate nature since such questions caused embarrassment during interview with consequent incomplete responses.     

Towards measurement of outcome for patients with varicose veins.

OBJECTIVE--To develop a valid and reliable outcome measure for patients with varicose veins. DESIGN--Postal questionnaire survey of patients with varicose veins. SETTING--Surgical outpatient departments and training general practices in Grampian region. SUBJECTS--373 patients, 287 of whom had just been referred to hospital for their varicose veins and 86 who had just consulted a general practitioner for this condition and, for comparison, a random sample of 900 members of the general population. MAIN MEASURES--Content validity, internal consistency, and criterion validity. RESULTS--281(76%) patients (mean age 45.8; 76% female) and 542(60%) of the general population (mean age 47.9; 54% female) responded. The questionnaire had good internal consistency as measured by item-total correlations. Factor analysis identified four important health factors: pain and dysfunction, cosmetic appearance, extent of varicosity and complications. The validity of the questionnaire was demonstrated by a high correlation with the SF-36 health profile, which is a general measure of patients' health. The perceived health of patients with varicose veins, as measured by the SF-36, was significantly lower than that of the sample of the general population adjusted for age and a lower proportion of women. CONCLUSION--A clinically derived questionnaire can provide a valid and reliable tool to assess the perceived health of patients with varicose veins. IMPLICATIONS--The questionnaire may be used to justify surgical treatment of varicose veins.     

An improved questionnaire for assessing quality of life after acute myocardial infarction

This paper reports our experience with the use of an improved self-administered questionnaire for assessing quality of life (QOL) after acute myocardial infarction. The modified questionnaire significantly increased the proportion of patients able to answer all questions from 84%–92%. The additional questions in the improved questionnaire increased the total variance explained by the Emotional, Physical and Social QOL factors from 65.8%–66.5%. Internal consistency and construct validity were assessed and found to be high. Overall, we have found that this improved questionnaire is easy to administer and that it possesses desirable properties of validity and reliability.This work was supported by a grant from the National Health and Medical Research Council of Australia (NH&MRC).     

Assessing the validity of the SF-36 General Health Survey

Our objective was to assess the validity of the SF-36 General Health Survey against the Social Maladjustment Schedule (SMS) and two questionnaire measures, the Social Problem Questionnaire and the Nottingham Health Profile (NHP) in a random subsample of 206 men and women from the Whitehall II study, a longitudinal survey of health and disease amongst 10,308 London-based civil servants. We found that social functioning on the SF-36 correlated significantly with social contacts, total satisfaction and total management scores on the SMS, and social isolation and emotional reactions on the NHP. General mental health on the SF-36 was associated with marriage, social contacts, leisure scores, total satisfaction and total management scores on the SMS, and emotional reactions, energy level and social isolation on the NHP. Conversely, physical functioning and physical role limitations were generally not associated with the SMS but were associated with physical abilities and pain on the NHP. In conclusion, this study offers evidence of the discriminant validity of the general mental health and physical functioning scales of the SF-36. We also found moderate construct and criterion validity for the social functioning scale of the SF-36 and considerable overlap between the general mental health and social functioning scales.