Independent variables.

In this study we did not use measures specifically designed to assess the IPT such as the Interpersonal Needs Questionnaire (INQ, [30]). Instead, we used various items from our questionnaire to create proxy scales of belongingness and burdensomeness. This approach has several limitations and we took particular effort to validate the constructs. Firstly, the three first authors reviewed the questionnaire and, independently, selected items that they thought were strongly related to the constructs. Secondly, the list of the items was then reviewed by the authors, retaining only the items that proved to be consistent across lists. Thirdly, discrepant items were discussed and a decision was made by consensus about whether to retain or exclude these items. Fourthly, Cronbach’s alpha coefficients were calculated to determine reliability of the proxy scales.

The Perceived burdensomeness and thwarted belongingness scale contains 14 items (7 for each subscale). The items rated the current state or the last two weeks but some items specify both current and past 5 years. Globally the time frame is the current state. The alpha Cronbach was 0.75 with a mean inter-item correlation of 0.18. The perceived burdensomeness subscale (PB) comprised seven items (see Table 1). The alpha Cronbach was 0.57 with a mean inter-item correlation of 0.17. The correlations between each item and the total score were significant and ranged from 0.31 to 0.53 with a mean of 0.44. The seven items of the PB correlated weakly with the thwarted belongingness scale (TB) score. The values ranged from 0.05 (not significant) to 0.3 with a mean value of 0.18. The TB comprised seven items (see Table 1). The alpha Cronbach was 0.64 with a mean inter-item correlation of 0.21. The correlations between each item and the total score were significant and ranged from 0.33 to 0.6 with a mean of 0.49. The seven items of the TB correlated weakly with the PB score; the values ranged from 0.07 (not significant) to 0.33 with a mean value of 0.19. TB and PB were significantly correlated (Spearman’s rho = 0.38, p <0.05).

Anhedonia (ANH-BDI-13): We used the short form of the Beck Depression Inventory (BDI-13) that contains 13 of the 21 items of the original scale introduced in 1961. The items of the BDI-13 and BDI were numbered using capital letters. The BDI-13 comprised 13 items from item # A “Mood” to item # M “Loss of appetite” and the BDI comprised 21 items from item # A “Mood” to item # U “Loss of libido”. The capital letters assigned to items from the BDI-13 were in no way linked to the capital letters assigned to items from and the BDI (e.g. the item rating social withdrawal is numbered # H in the BDI-13 and # L in the BDI). The French version of the BDI-13 has satisfactory psychometric properties. In the present study, the alpha Cronbach was 0.91 with a mean inter-item correlation of 0.6.

In 1996, the BDI-II has been developed in order to adhere more closely to the diagnostic criteria for major depressive episode in the DSM-IV. Contrary to the original BDI and BDI-13, the items of the BDI-II were numbered using Arabic numerals from # 1 “Sadness” to # 21 “Loss of interest in sex”. The item “work inhibition” was dropped from the BDI and replaced by a “loss of energy” item in the BDI-II.

To facilitate the comprehension we used only the Arabic numerals for the items.

Anhedonia was rated using the anhedonia subscale of the BDI as used by Joiner et al. [31]. The anhedonia subscale contains three items (item # 4: lack of satisfaction, item # 12: social withdrawal or loss of interest and item # 21: loss of interest in sex). Other authors [18, 32] included loss of energy (item # 15) in the anhedonia subscale whereas Joiner [31] or Leventhal [33] did not. All of these authors used either the original BDI [31], or the revised version (BDI-II) [18, 32, 33].

Item # 4 rates a lack of satisfaction in the BDI and loss of pleasure in the BDI-II. Item #12 rates social withdrawal in the BDI and loss of interest in the BDI-II. The phrasing of item # 12 in both cases is quasi-identical: in the BDI, the item rates the loss of interest in other people, whereas, in the BDI-II it rates a loss of interest in other people or activities. Thus, in the BDI item # 12 is centered only on people. Item # 21 (Loss of libido), however, is very similar in the original and revised versions of the BDI.

The short form of the BDI includes 3 items of the original version that can be used to rate anhedonia: item # 4 (Lack of satisfaction), item # 12 (Social withdrawal or loss of interest) and item # 15 (Work inhibition).

Joiner et al. [31] reported low reliability (alpha coefficient of 0.57) of the anhedonia subscale in their study of 102 patients presenting either major depression or schizophrenia. However, in two other samples the values of the alpha coefficients were higher (0.69 and 0.73). In the BDI-13, loss of interest in sex was not included. Instead, three other BDI items were used: Lack of satisfaction (LS-BDI-13) (ranging from 0: “I am not particularly dissatisfied” to 3: “I am dissatisfied with everything”); Loss of interest (LI-BDI-13) (ranging from 0: “I have not lost interest in other people” to 3: ”I have lost all interest in other people and don’t care about them at all.”); Work inhibition (WI-BDI-13) (ranging from 0: “I can work as well as before” to 3: “I can’t do any work at all”). The alpha Cronbach for this three-item scale was 0.59 with a mean inter-item correlation of 0.33.

The BDI items are rated using statements that best describe how the subjects have felt during the previous 2 weeks. Thus, the BDI evaluates recent changes or recent depressive symptoms. As the SLIPS [11], the anhedonia subscale of the BDI rates both the recent (or change) anticipatory and consummatory components of anhedonia.

Cognitive/affective symptoms of depression (CA-BDI-13) were assessed using the summation of four items of the BDI-13: sense of failure, guilt, self-hate and self-body image. The alpha Cronbach was 0.71 with a mean inter-item correlation of 0.38. Winer et al. [18] used a 6-item subscale of the BDI-II to measure the cognitive/affective symptoms of depression. Four of these six items were identical to the abridged version of the BDI and were chosen for the present study, thus allowing a comparison between our results and the Winer et al. study [18].

Clinical specialties: The following specialties were taken into account: paediatrics, obstetrics and gynaecology, clinical laboratory specialties, anaesthesiology and intensive care medicine, surgery (including ophthalmologists and otolaryngologists), radiology (including radiation therapy and nuclear medicine), internal medicine (including rheumatology, oncology, hematology, nephrology, geriatry, pulmonary medicine, cardiology, endocrinology, gastroenterology) psychiatry and child psychiatry, and general practice. Previous studies on stress, burnout or suicide in physicians used similar classification of specialties [34, 35]. A marked difference in prevalence of suicide has also been observed between medical specialties, with psychiatrists and anaesthesiologists being at greater risk of suicide compared to other physicians. Paediatricians and radiologists appear to have the lowest risk [36].