This was a cross-sectional study.

This study was conducted from 2024.01 to 2024.05 at West China Stomatology Hospital of Sichuan University. The initial sample size (384) was calculated with the following equation:

N = Z 2 × ( P × ( 1 − P ) ) E 2 (Z = 1.96, E = 5%, and P = 0.5). Considering the possibility of sample dropout, the overall sample size should be 1.2 times the calculated sample size, i.e., 460 participants. To ensure the representativeness of the sample, the following strict inclusion criteria were formulated: (1) patients aged between 18 and 65 years; (2) patients whose permanent dentition was complete except for third molars; (3) patients diagnosed with Class II or III DFDs by two physicians at a tertiary care hospital; and (4) patients who were informed and consented to participate in this study. The following exclusion criteria were applied: (1) Patients with other types of DFDs (except for sagittal displacement), such as laterognathism of the mandible, hemimandibular hypertrophy, unilateral micrognathia, hemifacial microsomia, and hemifacial atrophy et al; (2) patients with tooth loss (other than the third molars) in the permanent dentition; (3) patients with previous orthodontic treatment; (4) patients with temporomandibular joint disorders, craniofacial deformities such as cleft lip and cleft palate, severe periodontal disease, and/or severe tooth wear or mispositioning; (5) patients suffering from cognitive impairment and/or psychiatric disorders (for example, individuals with schizophrenia or dementia) and those with an inability to communicate due to severe psychiatric disorders; and (6) patients suffering from severe somatic disorders such as cancer, coronary heart disease, and/or aortic dissection.

A total of 500 patients were diagnosed with different types of DFDs at the West China Stomatology Hospital of Sichuan University. A total of 492 patients were invited to participate in this study after meeting the inclusion criteria. A total of 481 patients agreed to participate in this study. Finally, 471 patients with available answer sheets were included in this study. The details of the sampling process are presented in Figure 1 .

An online questionnaire was developed by using WJX software to collect data (), which included three components: patients’ demographic characteristics, patients’ esthetic expectations, and patients’ depression status. Before the formal investigation, the aims, methodology, and precautions of this survey were explained to the participants by one researcher. Then, each participant signed an informed consent form. The online questionnaire was subsequently forwarded to the participants by the researcher for completion.

Strict quality control measures were adopted to ensure the authenticity and rigor of this study. For example, a questionnaire could be submitted only if it took a participant more than two minutes to complete it. The participants could submit the answer sheet only if all the questions were completed. Questionnaires in which only one option for all the items was selected were excluded. Questionnaires in which opposite answers were selected for similar questions were also excluded. All questionnaires were automatically reviewed by the software and then manually verified by the researcher. Overall, 471 questionnaires were collected.

IBM SPSS 26.0 was used to analyze the data in this study. Frequencies and percentages were used to analyze participants’ demographic characteristics, esthetic expectations, and depression status. Differences in depression between groups were detected by the chi-square test, with a significance level of P< 0.05 considered statistically significant in multiple tests. Multivariate logistic regression was used to detect the relationships between the selected factors and patients’ depression status.

Before the research was conducted, all the details about this study, including the research objectives, research tools, and participant information, were carefully reviewed by the Ethical Committee of West China Stomatology Hospital, Sichuan University. This study was approved by the Ethical Committee of West China Stomatology Hospital, Sichuan University (NO. WCHSIRB-D-2023-333). Furthermore, owing to the sensitivity of the research topic, the privacy of the respondents was strictly protected before the investigation was conducted. Primary data were available only to the researchers. All the data were adopted only for academic research. Before the survey started, all the participants were informed about the research objectives, methods, tools, and any other details and consented to participate in this survey.

A total of 471 participants were enrolled in this study. Most of the participants were women (337, 71.5%). A total of 30.8% of the participants were between 21 and 25 years old. Nearly half of the participants had obtained a bachelor’s degree (211, 44.8%). A total of 35.9% of the participants had a salary of 5001–10000 yuan per month. Most of the participants (76.9%) were unmarried. All the details about the participants’ demographic characteristics are shown in ( Table 1 ).

In this study, 308 patients were diagnosed with Class II DFDs, whereas 163 patients were diagnosed with Class III DFDs ( Table 1 ).

The results of this study indicated that nearly half of the patients’ esthetic expectations (240, 51.5%) were extremely high, whereas 75 patients’ esthetic expectations were extremely low. All the details about the participants’ esthetic expectations are shown in ( Table 1 ).

According to the classification criteria for the PHQ-9, scale scores of 0-4, 10-14, 15-19, and 20-27 indicate mild, moderate, moderate-severe, and major depression, respectively. In this study, 322 (68.4%) DFD patients did not have depression, whereas 149 (31.6%) patients had mild depression or above ( Table 1 ).

The results of the chi-square test indicated that demographic information, educational background, and monthly income were related to depression in patients with DFDs. Furthermore, patient depression might be affected by patients’ esthetic expectations and DFD classification ( Table 1 ).

The results of logistic regression demonstrated that, compared with DFD patients who had a master’s degree or above, those with a high school education were more prone to depression (OR=3.848, 95% CI: 1.546-9.574). Compared with Class II DFDs, Class III DFDs were associated with a greater risk of depression (OR=1.458, 95% CI: 1.007–2.078). Compared with those who had extremely low esthetic expectations, patients who had extremely high esthetic expectations (OR: 2.25, 95% CI: 1.053–4.086) were more prone to depression ( Table 2 ).

Depression, which is characterized mainly by a low mood, loss of interest, and lack of energy, can not only significantly exacerbate the risk of self-inflicted harm and suicide but also significantly reduce the success rate of orthognathic surgery and exacerbate postoperative pain in patients with DFDs (6, 14, 15, 32). The results of this study revealed that the incidence of depression in DFD patients was 31.6%, which is significantly greater than that reported in the general population and is consistent with the results of Sebastiani et al (6, 9). Since DFDs can increase the risk of depression in patients and the prevalence of DFDs is as high as 20% in the global population, the significance of interventions for existing as well as future depression in the DFD population is highlighted by this study (1, 6, 12).

Regression analysis indicated that, compared with patients who had a master’s degree or above, patients who had a high school education were more vulnerable to depression. Similar findings have been obtained in other studies of non-DFD populations (33–35). On the one hand, a higher education level is often associated with better socioeconomic status. According to health inequality theory, people with higher education levels have more psychological and material capital to withstand life’s stresses and are more resilient to risky events, thus reducing their risk of depression (34). On the other hand, there may be differences in the cognition of people with different levels of education. When personal appearance is overly mythologized, highly educated people may be more rational, developing a more objective view of their facial features (36). Therefore, psychosocial interventions should be provided to patients with DFDs according to their cognitive level, and psychological resilience should be promoted in patients with low education and socioeconomic levels.

Regression analysis indicated that, compared with Class II DFD patients, Class III DFD patients were more vulnerable to depression. These results are consistent with those of Burden et al., who reported that patients with Class III DFDs were significantly less confident in their appearance than patients with Class II DFDs (37). Sen et al. reported that, compared with Class II DFD patients, Class III DFD patients held more negative opinions about their profiles and considered themselves even more unattractive (38).

Skeletal Class III malocclusion is one of the most prevalent DFDs and is defined as maxillary retrusion, mandibular protrusion, or a combination of both, and the positions of the maxillary and mandibular jaws in patients with Class III DFDs are opposite those of the normal position (2, 39). In general, Class III DFD patients present with anomalies and severe mental distress due to mandibular protrusion and maxillary deficiency (39). Owing to the location of the jawbone defect, patients with Class III DFDs might have greater degrees of social impairment and physical pain than those with Class II DFDs (38). A greater need for orthognathic surgery and greater improvement in quality of life in patients with Class III DFDs after orthognathic surgery than in those with Class II DFDs have also been reported in previous studies (39–41). Thus, Class III DFD patients may have a greater degree of distress to their appearance, occlusion, perceived low appraisal by others, etc., resulting in greater susceptibility to psychological problems such as depression. To support this hypothesis, the present study further explored the relationship between the type of DFDs and patients’ esthetic expectations, and the results revealed that, compared with patients with Class II DFDs, patients with Class III DFDs had significantly greater esthetic expectations. This explains another aspect of the emergence of the phenomenon.

Therefore, for patients with DFDs, targeted psychological interventions should be provided according to the type and location of the jaw defect. Attention should be given to boosting self-confidence, correcting negative self-perceptions, and improving depression in patients with Class III DFDs.

Regression analysis indicated that, compared with patients whose esthetic expectations were extremely low, patients whose esthetic expectations were extremely high were more vulnerable to depression. The results of this study are consistent with Pikoos et al. (42). Esthetic expectations are defined as the extent to which a patient wishes to improve his or her appearance through surgery (27). Esthetic expectations contribute to enhancing patients’ compliance with surgery while also increasing their risk of psychological disorders, which is a “double-edged sword” (9). Studies of patients undergoing plastic surgery have demonstrated that these patients experience higher levels of emotional distress about their appearance than the general population does and that improving their appearance is the most important motivation for undergoing surgery. When plastic surgery patients have excessive expectations, their risk of depression is significantly greater (42–44).

Patients are more likely to develop somatoform dysmorphic disorders and negative cognition about their appearance when they are overly concerned about their facial defects and present high levels of esthetic expectations (43). Patients may even fall into the vicious circle of “inappropriate cognition– negative emotions–distorted cognition” (45). According to Beck’s cognitive theory of depression, cognitive components and cognitive processes are susceptibility factors for depression. When an individual develops cognitive biases, as soon as a negative event occurs, negative automated thoughts are generated, followed by depression (46).

Therefore, in psychological interventions for patients with DFDs, patients’ esthetic expectations for surgery should be assessed, and unrealistic expectations and biased perceptions should be corrected to reduce the risk of depression in these patients.

Depression is a serious psychiatric disorder that significantly contributes to the global burden of disease. Previous studies have shown that patients with DFDs are at increased risk of comorbid depression. However, the causes of comorbid depression in patients with DFDs remain unclear. The results of this study suggested that a low education level, class III DFD, and high esthetic expectations were risk factors for depression in patients with DFDs and clarified the potential causes of comorbid depression in some patients with DFDs, which can help health care professionals provide targeted psychological interventions according to patients’ different cognitive levels, types of disorders, and expectations and reduce the prevalence of depression in patients with DFDs.

This study has several limitations. First, a convenience sampling method rather than random sampling was used, which may have resulted in bias, and the sample included only 471 patients. This may lead to the sample being unrepresentative. Subsequent studies should increase the sample size to increase representativeness. Second, this was a cross-sectional study that was unable to explore the process by which individuals’ mental states are affected by DFDs. Therefore, longitudinal studies are needed. Third, deformities other than those in the sagittal plane may also cause depression in patients; for example, laterognathism of the mandible may also contribute to depression. To avoid the bias caused by this influence, this study did not include DFDs other than sagittal deformities. This may have resulted in the results of the study being limited to patients with Class II and Class III DFDs and may not be applicable to patients with other malformations. Therefore, future studies should also expand the scope of the discussion of types of DFDs. Furthermore, the present study did not discuss the effect of the severity of skeletal deformity on depression in patients, which is one of the limitations of this study. Future studies should explore the effect of the severity of skeletal deformity on patient depression based on quantitative indicators such as the ANB angle and wits value to deepen the understanding of the effect of DFD on patients’ psychological status. Finally, this study explored only the effects of demographic factors, disease type, and esthetic expectations on depression in patients with DFDs; however, numerous factors influence depression in patients with DFDs, and therefore, future studies should consider additional influencing factors.