This study is a retrospective observational analysis of inpatients who received psychiatric consultations at a general center in Seoul, South Korea. Data were extracted from the institution’s electronic medical record system, covering an exhaustive review of 1,286 initial psychiatric consultation requests over a 7-year period (2005–2011). This sample size was based on all eligible cases during the study period who met the inclusion criteria.

The study population was restricted to adult inpatients whose final psychiatric diagnoses were confirmed as insomnia (n=236), anxiety disorders (n=601), or depressive disorders (n=449). To ensure diagnostic homogeneity and the validity of the results, the following inclusion and exclusion criteria were applied:

Inclusion criteria were as follows : 1) the first psychiatric consultation occurring within the study period; 2) a clearly documented psychiatric diagnosis based on DSM-IV-TR criteria at the time of consultation; and 3) complete availability of key clinicodemographic variables, including age, sex, referring department, number of consultations, reconsultation status, and consultationrequest type. Diagnostic group assignment was based exclusively on the final psychiatric diagnosis documented in the official consultation record according to DSM-IV-TR criteria, rather than on the wording of the referral request or chief complaint. Reconsultation was defined as cases in which two or more psychiatric consultations were conducted for the same patient.

Exclusion criteria were: 1) cases with comorbid psychiatric diagnoses whose primary diagnoses could not be clearly determined; 2) incomplete consultation records or missing documentation of CR type; and 3) patients under 18 or over 85 years of age. Patients aged over 85 years were excluded to minimize clinical heterogeneity associated with extreme old age, including a higher prevalence of cognitive impairment and delirium, which could confound consultation patterns.

The study protocol was approved by the Institutional Review Board (IRB) of Konkuk University Medical Center (Approval No. 2026-01-052) and was conducted in strict accordance with the ethical principles of the Declaration of Helsinki. Given the retrospective nature of the chart review, the requirement for individual informed consent was waived, and all personal identifiers were anonymized to ensure patient confidentiality.

Consultation referral pathways were classified using the functional model proposed by Vaz and Salcedo (1996) [14]. This framework categorizes the role of psychiatric intervention based on the timing of symptom onset and its relationship with the primary medical condition as follows:

- Complementary (CR1): Cases where psychiatric care complements or supports the primary treatment of the patient’s physical illness.

- Parallel (CR2): Cases requiring management of pre-existing psychiatric disorders that are independent of the current reason for hospitalization.

- Mending (CR3): Cases where acute psychiatric symptoms emerge after admission, requiring immediate symptomatic relief and short-term intervention.

- Antecedent-conditioned (CR4): Referrals prompted by a known history of psychiatric illness rather than current acute symptoms.

- Misdiagnosis-conditioned (CR5): Cases where non-psychiatric (somatic) symptoms were mistakenly attributed to psychiatric causes by the referring physician.

The classification of CR types was initially performed by a psychiatry resident and subsequently reviewed and finalized through discussion with a board-certified psychiatrist to ensure diagnostic consistency.

Statistical analyses were performed using SPSS version 27.0 (IBM Corp.). Descriptive statistics were utilized to summarize clinico-demographic characteristics, with continuous variables expressed as mean±standard deviation and categorical variables as frequencies and percentages.

To examine differences across the three diagnostic groups, one-way analysis of variance (ANOVA) followed by Tukey’s post-hoc tests was applied for continuous variables such as age and the number of consultations. Categorical variables, including sex, referring department, reconsultation status, and CR types, were compared using the chi-square (χ²) test. Effect sizes were calculated and reported as appropriate (eta-squared for ANOVA, Cramer’s V for chi-square tests).

To identify independent predictors of the Mending (CR3) pathway specifically for insomnia patients, a multivariable logistic regression analysis was conducted, adjusting for potential confounders such as age and sex. The results are presented as adjusted odds ratios (OR) with 95% confidence intervals (CI). Model fit was verified using the Hosmer-Lemeshow test. All statistical tests were two-tailed, and a p-value less than 0.05 was considered statistically significant.

A total of 1,286 patients were included in the final analysis: 236 in the insomnia group (18.4%), 601 in the anxiety disorder group (46.7%), and 449 in the depressive disorder group (34.9%). Significant age variations were observed among the three groups (F=25.10, p<0.001) (Table 1). The insomnia group had the highest mean age (61.96±14.26 years), followed by the depressive disorder group (59.02±16.93 years), while the anxiety disorder group was the youngest (53.40±19.04 years). Patients in the insomnia group were significantly older on average than those in the other two groups (p<0.001). Post-hoc analysis confirmed that the age differences between the insomnia and anxiety groups, as well as between the depressive disorder and anxiety groups, were statistically significant (p<0.001). Regarding sex distribution, the insomnia group had the highest proportion of males (54.7%), whereas females predominated in the anxiety (63.6%) and depressive disorder (68.4%) groups (χ²=36.13, p<0.001) (Figure 1). These findings underscore that inpatient insomnia, as defined by DSM-IVTR criteria, is more frequently observed in older male inpatients.

When classified by referring department, the insomnia group had the lowest proportion of referrals from internal medicine (53.0%) and a relatively higher proportion from surgical specialties (47.0%). In contrast, internal medicine was the primary source of referrals for both anxiety (64.1%) and depressive disorders (69.3%) (χ²=17.83, p<0.001) (Table 1).

Consultation intensity was notably lower for insomnia patients (Figure 1). The reconsultation rate was lowest in the insomnia group (27.5%), compared with 39.1% for anxiety and 48.6% for depression (χ²=29.04, p<0.001). Similarly, the mean number of consultations was lowest for insomnia (1.54±1.49), followed by anxiety (1.81±1.48) and depression (2.09±1.81) (F=15.47, p<0.001) (Table 1). These findings imply that inpatient insomnia consultations are more likely to be brief and focused on immediate symp-tom management, whereas anxiety and depressive disorders are associated with greater consultation intensity and continuity of psychiatric care.

The distribution of CR types (CR1–CR5) differed significantly across groups (χ²=91.87, p<0.001) (Table 2). In the insomnia group, CR3 (mending request) was predominant, accounting for more than half of all cases (51.3%) (Figure 2). This was significantly higher than the proportions observed in the anxiety disorder group (24.5%) and the depressive disorder group (36.7%). In the anxiety disorder group, CR1 (29.3%) and CR2 (33.6%) were the predominant request types, whereas in the depressive disorder group, CR2 (36.7%) and CR3 (36.7%) were nearly equally represented. CR4 was relatively more frequent in the anxiety disorder group (12.5%) but uncommon in both the insomnia and depressive disorder groups. CR5 was rare across all groups.

In a multivariable logistic regression analysis adjusted for age and sex, the insomnia group remained independently associated with a significantly higher likelihood of CR3 requests compared to the other groups (adjusted OR=2.41, 95% CI=1.65–3.52, p< 0.001) (Figure 2). These results indicate that psychiatric consultations for insomnia are primarily focused on immediate symptomatic relief for conditions such as acute sleep disturbance or pain-related insomnia rather than comprehensive or long-term intervention. In contrast, consultation requests for anxiety and depressive disorders more frequently reflected the need for diagnostic clarification or parallel psychiatric management of pre-existing conditions, rather than solely addressing acute symptoms.

This study contributes meaningfully by systematically characterizing CR types among inpatients with insomnia and identifying distinctive patterns associated with this group. In particular, applying the classification proposed by Vaz and Salcedo [14] to real-world clinical data allowed us to delineate the specific consultation characteristics associated with insomnia. Nevertheless, several limitations should be noted. First, the study was conducted retrospectively at a single institution, limiting generalizability to broader inpatient populations with insomnia, anxiety, or depression. In addition, this study included only patients who were referred for psychiatric consultation, which may introduce selection or referral bias, as consultation requests are influenced by clinicians’ perceptions, departmental practices, and institutional culture. Additionally, the study did not assess how consultation patterns influenced clinical outcomes. Future studies employing multicenter, prospective designs are needed to examine the impact of insomnia-related consultations on outcomes such as length of stay, readmission rates, and symptom improvement. Second, rare consultation types (e.g., CR4, CR5) were underrepresented, constraining interpretability. Furthermore, although analyses were adjusted for age and sex, other potentially important confounding factors—such as severity of medical illness, pain intensity, delirium risk, medication use, and ward characteristics—were not systematically controlled for, which may have influenced consultation patterns. Third, insomnia was analyzed as a single diagnostic entity, limiting our ability to consider the complex interplay between insomnia and co-occurring anxiety or depressive symptoms. Longitudinal research is warranted to determine whether CR3-dominant referral patterns effectively prevent or detect progression to anxiety or depression and whether early psychiatric intervention enhances long-term outcomes. Experimental studies examining the role of non-pharmacological strategies and multidisciplinary care models are also needed. Finally, the dataset reflects consultation practices from 2005 to 2011 and may not fully represent current patterns shaped by contemporary developments such as digitalized inpatient environments, expanded multidisciplinary consultation systems, and increased incorporation of non-pharmacological sleep interventions (e.g., CBT-I, environmental light adjustments). Future studies should replicate this analysis in modern clinical environments to evaluate temporal changes and ensure contemporary relevance.

This study demonstrated that inpatients with insomnia exhibit consultation request patterns distinct from those of patients with anxiety or depressive disorders. Notably, the predominance of Mending-type (CR3) consultation requests suggests that insomnia in the hospital setting is frequently managed with an acute, symptom-oriented approach, influenced by environmental disruption during hospitalization, physical conditions, and clinical perceptions that regard insomnia as a secondary symptom. However, reliance on CR3-focused management alone may overlook longer-term clinical risks and unmet therapeutic needs. Accordingly, multidimensional strategies—including early psychiatric involvement, environmental modification, sleep hygiene education, and appropriate pharmacological management—should be considered in routine inpatient care. Future multicenter, prospective studies with longitudinal follow-up are warranted to evaluate the effectiveness of both pharmacological and non-pharmacological interventions and to clarify how early, insomnia-focused psychiatric consultation influences long-term outcomes such as delirium, symptom persistence, readmission, and overall clinical trajectory.