2.1. Participants
The participants included three groups: patients with MDD (n=37, 54.05% females, mean age: 28.17, SD: 2.27), patients with SAD (n=35, 54.28% females, mean age: 27.49, SD: 2.06) and HC group (n=35, 48.57% females, mean age: 28.38, SD: 3.41). Patients with MDD and SAD were recruited from four psychological services clinics in Sari, Iran. Patients were diagnosed with MDD or SAD according to the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I)38.
Exclusion criteria for two patient groups were the following: a) any current or past diagnosis of a psychotic disorder, and/or b) autism spectrum or any developmental disorders, and/or c) bipolar disorder and/or d) any neurological diseases such as epilepsy, Parkinson's disease, or severe head injury. Also, they were excluded if they had any substance abuse issues during the preceding six months. Moreover, patients in the SAD group were excluded if they had any history of major depression.
The healthy control (HC) group was recruited from the Islamic Azad University in Sari, Iran. None of the participants in the HC group had a history of any DSM-IV Axis I or Axis II disorders, a brain injury, neurological diseases, and/or evidence of current or past substance abuse.
All participants satisfied the following criteria: they all were a) at least 20 years old, b) capable of understanding the experimental procedure, and c) had normal visual and auditory senses. The ethics committee of the Faculty of Psychology and Education of Shahid Beheshti University approved the procedure. All of the participants gave written informed consent.
2.2. Clinical assessment
For both patient groups, diagnoses were established by the Persian version of Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I)38. All participants completed the Persian version of Beck Depression Inventory-II (BDI-II)39 and the Persian version of the Beck Anxiety Inventory (BAI)40 to assess the severity of depression and anxiety symptoms, respectively. The BDI is a 21-item self-report measure developed to assess the attitudes and clinical symptoms in both depressed and non-depressed psychiatric patients.41 The BAI is a 21-item self-report measure, which evaluates the severity of anxiety symptoms and can differentiate between anxiety and depression.42 In previous studies, the Persian versions of the BDI-II and the BAI had good psychometric properties.39,40 We also employed the Wechsler Adult Intelligence Scale-Revised Version (WAIS-R)43 to assess overall intellectual functioning.
2.3. TOM tasks
2.3.1. Reading in the mind of the eyes Task
To measure the decoding of mental states (i.e., affective aspect) of ToM, we utilized the Reading in the Mind of the Eyes test (RMET)32 translated into Persian44. This test consists of 36 black-and-white photographs of the same size (15cm×6cm) from the eyes area of confederate actors. Three mental states are presented (i.e., neutral, negative, and positive), and the participant is asked to select the option which could best represent the mental state of the picture. Moreover, as a control task, volunteers were required to express their opinions on the gender of each picture (i.e., gender recognition). There was no time limit for answering questions. The total score of each participant in the two tasks was calculated based on the total participant’s correct response to each picture; the highest score a participant can acquire is 36. In addition to the two above-mentioned scores, in agreement with the Harkness et al.45 study and the Richman & Unoka31 pattern, three subscales were also calculated based upon the value of each mental state. Following this pattern, the 36 photographs fit into three separate categories depending on the positive, negative, and neutral values of each mental state (i.e., 8 positive, 12 negative, and 16 neutral). Previous studies have indicated the attentional bias to negative stimuli in depressed individuals46,47; therefore, in this study, we used such scoring for accurate differentiation of three groups in discrimination of positive and negative mental states.
2.3.2. Faux Pas Task
The faux pas task was used to assess the reasoning mental states (i.e., cognitive aspect) of ToM. This test composed of 20 short stories; half of them included a faux pas while the other half excluded a faux pas, considered as control stories. According to Baron-Cohen et al.48, the Faux Pas occurs when a speaker says something without considering if it is something that the listener might not want to hear or know; it typically has negative consequences that the speaker never intended (See Appendix 1). There were no time limits, and therefore, to understand the story entirely, volunteers could read it repeatedly. At the end of every story, there were two faux pas questions together with two control ones. The faux pas questions were about the main character’s intentions and were designed to assess the participant’s thorough understanding as to whether or not they could recognize that a faux pas had occurred in the story.
The control questions aimed to check the reader’s full comprehension of the story. In the Faux Pas Task, participants who answered “yes” to the first question (In the story you just read, has there been a faux pas and/or an embarrassing mistake in a social situation?) were required to answer the next faux pas question; meanwhile, in the stories involving a faux pas, one score was saved for each correct response. In case the subject’s answer to the first question was “no”, they were not asked the consequent question; however, all participants were required to answer the two control questions, even if their answers to the first question had been negative. Ultimately, 20 was the maximum score a participant could achieve on the Faux Pas Questions, and 40 on the control ones.
2.4. Statistical analysis
All statistical analyses were performed using SPSS 23. In data analysis, we compared the affective and cognitive dimensions of the theory of mind in the three groups of MDD, SAD, and HC by a Multivariate analysis of variance (MANOVA).