Limited effect of screening for depression with written feedback in outpatients with diabetes mellitus: a randomised controlled trial

Data were collected in three tertiary diabetes clinics from different regions in the Netherlands: the VU University Medical Centre (Amsterdam), Radboud University Medical Centre (Nijmegen) and Haaglanden Medical Centre (The Hague). Each clinic serves a patient population of approximately 2,000 diabetes patients, both type 1 and type 2. A random sample of a total of 2,055 outpatients was drawn from the three respective clinics (Amsterdam n = 1,000; (The Hague n = 555, Nijmegen n = 500)). Baseline data has been previously described in detail [25, 26].

At baseline, participants received questionnaire booklets by mail in two waves: the first assessing socio-demographics, clinical data and diabetes-specific distress. The second captured depression and mental healthcare consumption. We chose to separate the two booklets in order to avoid over-burdening the respondents. Patients were invited to return the questionnaires in pre-stamped envelopes to the research team. Inclusion criteria were: (1) adult (≥18 years); (2) outpatient with established diabetes (type 1 or type 2); and (3) elevated depression score (Centre for Epidemiologic Studies Depression Scale (CES-D) score of 16 or more). Exclusion criteria were: (1) not being able to read Dutch; (2) a history of suicide attempt(s); (3) a history of hospital admission for depression; and (4) a history of electroconvulsive therapy (ECT) for depression. After completion of the depression questionnaire, respondents who met inclusion criteria were randomly assigned to: (1) CAU; or (2) the screening procedure (SCR). We randomised the participants using computer generated random numbers by SPSS. Allocation could not be completely concealed, due to the fact that physicians also received a copy of the letter regarding the outcome of the diagnostic psychiatric interview, and thus at least knew which participants were allocated to the intervention group. In the Netherlands, standard outpatient diabetes care generally consists of, on average, four regular appointments with an internist and/or diabetes nurse specialist. If needed, other members of the diabetes team can be consulted, such as a dietitian, podiatrist, ophthalmologist or medical psychologist [27]. It is important to emphasise that in the control group (CAU) the assessment of emotional well-being was not followed by feedback to patients and/or healthcare providers. Patients in the SCR group were invited for a Composite International Diagnostic Interview (CIDI), using the sections: Mood Disorders and Anxiety Disorders, allowing for a Diagnostic and Statistical Manual for Mental Disorders (DSM-IV) diagnosis [28]. In the case of a diagnosis of a mood disorder and/or an anxiety disorder, the patient, as well as his/her diabetes specialist and general practitioner, received a letter with the DSM-IV diagnosis, and advice regarding treatment options for depression and/or anxiety. When no mood or anxiety disorder was detected, the patients also received a letter with the outcome of the interview and the advice to contact their physician in case symptoms of depression/anxiety should worsen, as minor depression is known to be an important risk factor for the development of major depression in diabetes [29]. All patients received a brochure developed by mental health professionals and patients, supported by the Dutch Psychological Health Foundation (Fonds Psychische Gezondheid), about depression and its treatment. This brochure contains seven pages of information about the symptoms, the potential causes and the prevalence of depression. It also stresses the importance of seeking treatment, for example cognitive behavioural therapy or use of antidepressant medication. Finally, the brochure provides several useful addresses/phone numbers where patients can acquire further information and suggestions for self-help books (see www.​psychischegezond​heid.​nl/​dynamic/​media/​1/​files/​depressie.​pdf for the brochure [in Dutch].

At the 6 month follow-up, depression and diabetes-distress were reassessed by means of a mail questionnaire. Written informed consent was obtained from all participants and the study was approved by the local medical ethics advisory committee. The investigations were carried out in accordance with the principles of the Declaration of Helsinki as revised in 2000. The present study was not registered as a clinical trial, as the data collection in the three clinics took place between 2003 and 2007 and thus started before the prospective trial registries commenced (2005).

This first questionnaire contained questions on: being single/having a partner, ethnic background (native Dutch, Turkish, Moroccan, or from Surinam, the Netherlands Antilles, Indonesia, or other), highest level of completed education, alcohol consumption and smoking. From the medical records of the patients, the following data were extracted: age, sex, type of diabetes, duration of diabetes, microvascular complications (retinopathy: background or proliferative, nephropathy and neuropathy), cardiovascular disease, most recent HbA_1c and blood pressure.

To assess symptoms of depression, the Dutch version of the CES-D scale was used [30, 31]. This is a 20-item, self-report scale that asks respondents to indicate the frequency of occurrence of 20 depressive symptoms during the previous week. The instrument uses a four-point response set, ranging from ‘rarely or none of the time’ to ‘most of the time or always’. Higher scores indicate more depressive symptoms and a cut-off point of 16 or more is generally accepted as indicative of a clinically significant level of depression symptoms [30, 31]. The automated World Health Organization CIDI-auto is a structured diagnostic interview, which was used to determine whether the patients suffered from a depressive disorder and/or an anxiety disorder, according to DSM-IV criteria [28, 32, 33]. The main advantage of the CIDI-auto is that the questions are fully specified. In our study, lay interviewers, mostly medical or psychology masters students, were trained by a certified CIDI interviewer (FP) to use the CIDI-auto. These interviewers were not blinded to group assignment.

Diabetes-specific emotional distress was assessed using the Dutch version of the PAID survey [34, 35]. This questionnaire consists of 20 items, which can be rated on a five-point Likert scale ranging from 0 (no problem) to 4 (serious problem). Examples of items are: ‘Not accepting diabetes’, ‘Worrying about the future and the possibility of serious complications’, ‘Feeling overwhelmed by your diabetes regimen’ or ‘Feeling alone with diabetes’. Following the recommendation of the measure’s authors, the PAID questionnaire scores are transformed to a scale of 0–100, higher scores indicating more serious emotional problems.

Statistical analyses were performed using SPSS version 16.0 (SPSS Inc., Chicago, IL, USA). The primary outcome variable was depression score; diabetes-distress, mental healthcare use and HbA_1c were regarded as secondary outcomes. The present study has sufficient power to detect a medium effect size of f = 0.25. For example, the correlation between two time measures of CES-D depression score was assumed to be moderately large r(m1, m2) = 0.50. Moreover, with a population standard deviation of the CES-D (each group) equalling 8, the present study was able to detect a difference of four points in CES-D change scores between the two treatment groups with a power of 0.93. The CES-D depression scores can range from 0 to 60 as, for each of the 20 items, the scores range from 0 to 3.

Continuous demographic data for the participants were analysed using independent means t tests, and χ ² tests were used for categorical variables. A p value <0.05 was considered to be statistically significant. Data were analysed according to the intention-to-treat principle with the baseline value carried forward in cases of missing follow-up data. First, by means of t tests and χ ² tests, baseline variables were compared between the intervention and CAU group. Then, general linear model repeated measures were conducted with the CES-D as dependent variable, with two independent variables: time (within-participant) and group (between-participant). The same analysis was performed with the PAID scores or HbA_1c as dependent variable.