Allergic rhinitis represents one of the most widespread chronic atopic disorders globally, significantly disrupting sleep quality, cognitive performance, daily productivity, and emotional well-being. Clinicians have increasingly adopted sublingual immunotherapy as a targeted disease-modifying intervention designed to induce long-term allergen tolerance. However, because chronic systemic allergic inflammation shares complex neuroimmune pathways with mood and affective disorders, researchers have actively sought to evaluate whether allergen desensitization alters neuropsychiatric outcomes. A crucial clinical question revolves around whether initiating sublingual immunotherapy alters the subsequent risk of depression or influences antidepressant prescribing patterns. A recent nationwide Japanese pharmacoepidemiological investigation has provided robust real-world evidence clarifying this relationship. Consequently, understanding these findings enables clinicians to navigate immunotherapy safety profiles with greater diagnostic confidence and ensure holistic psychiatric and immunological patient care.

Neuroimmune Cross-Talk and Allergic Sensitization

Allergic respiratory diseases involve substantial neuroimmune interactions that extend well beyond localized mucosal surfaces. Specifically, systemic cytokines such as interleukin-4, interleukin-5, and interleukin-13 can traverse the blood-brain barrier, potentially modulating microglial activation and central monoaminergic neurotransmission. Furthermore, persistent physical symptoms, severe nasal obstruction, and chronic sleep fragmentation frequently exacerbate psychological distress, creating a bi-directional vulnerability toward clinical depression and generalized anxiety disorders. Therefore, physicians often encounter higher baseline rates of mood disturbances among patients suffering from severe allergic rhinoconjunctivitis. In response to this complex clinical interplay, researchers hypothesized that successful allergen-specific desensitization might reduce neuroinflammation and improve psychological outcomes. Conversely, some clinical observers raised questions regarding whether the intensive immunological stimulation inherent to allergen administration could provoke adverse affective changes. Thus, systematic investigation of real-world prescriptive patterns serves as an indispensable step toward demystifying neuropsychiatric trajectories in atopic populations.

Sublingual Immunotherapy Evaluation in a Nationwide Cohort

To rigorously examine these clinical hypotheses, investigators conducted an extensive retrospective cohort study utilizing a comprehensive nationwide administrative claims database in Japan spanning from 2014 to 2021. The study focused specifically on adult patients diagnosed with Japanese cedar pollinosis, comparing new users of sublingual immunotherapy against matched non-users. In real-world healthcare environments, patients opting for immunotherapy often demonstrate distinctive baseline health-seeking behaviors and comorbidity profiles. Indeed, prior to statistical adjustment, mental health disorders appeared significantly more prevalent among the sublingual immunotherapy cohort than among non-users, despite comparable baseline allergic rhinitis severity. Consequently, the research team implemented sophisticated 1:1 propensity score matching to balance essential baseline variables, including patient age, sex distribution, insurance category, and detailed medical comorbidities. This meticulous analytical approach yielded 3,991 precisely matched patient pairs, effectively eliminating confounding variables and isolating the specific longitudinal impact of sublingual desensitization on subsequent psychiatric pharmacotherapy.

Propensity-Matched Outcomes for Antidepressant Initiation

The primary clinical endpoint evaluated across the matched cohorts was the de novo initiation of antidepressant prescriptions during the follow-up period. Prior to propensity matching, crude incidence rates of antidepressant initiation stood at 5.0 per 1,000 person-years among immunotherapy recipients, compared to 2.9 per 1,000 person-years among non-users. However, after rigorous propensity score balancing accounted for baseline psychiatric disparities, this apparent difference completely dissipated. The multivariable-adjusted analysis revealed a hazard ratio of 1.11 with a 95% confidence interval spanning from 0.73 to 1.69. Furthermore, longitudinal Kaplan-Meier survival curves demonstrated no statistically significant differences in antidepressant-free survival between the matched treatment arms over time. Therefore, the empirical evidence demonstrates that undergoing sublingual immunotherapy neither elevates nor substantially reduces the subsequent likelihood of initiating antidepressant therapy. These robust findings effectively reassure healthcare practitioners regarding the neuropsychiatric safety profile of sublingual allergen tablets and drops.

Clinical Implications for Primary Care and Specialist Practice

These pharmacoepidemiological insights offer several vital practice points for primary care physicians, allergists, pulmonologists, and otolaryngologists. First, the data clearly confirm that sublingual immunotherapy does not cause psychiatric destabilization, allowing practitioners to prescribe allergen-specific desensitization without fear of triggering clinical depression. Second, the observed baseline differences emphasize that atopic individuals actively seeking advanced allergen therapies often carry preexisting psychological burdens. Therefore, clinicians must remain vigilant in evaluating baseline mental health independent of allergy treatment choices. Additionally, healthcare providers should incorporate validated mood screening tools during routine atopic assessments, particularly when patients present with chronic fatigue, persistent insomnia, or unremitting nasal congestion. Moreover, recognizing that allergic symptom relief does not automatically replace mental healthcare ensures that patients receive timely multidisciplinary support. Thus, clinicians should foster collaborative care pathways connecting allergy specialists with psychiatry and behavioral health professionals whenever mood disturbances emerge.

Optimizing Comprehensive Atopic and Psychological Management

Achieving optimal therapeutic outcomes in allergic rhinitis requires a comprehensive, dual-focused management paradigm. While allergen immunotherapy effectively modifies underlying mucosal and systemic immunological responses, it operates alongside rather than in place of targeted mental healthcare. Consequently, clinicians must educate patients that sublingual immunotherapy specifically targets allergic cascades, such as eosinophilic infiltration and immunoglobulin E-mediated pathways, without functioning as a primary treatment for depressive disorders. Furthermore, future clinical trials with extended follow-up windows and granular psychiatric rating scales are necessary to evaluate subtle quality-of-life shifts that administrative claims databases cannot fully capture. Meanwhile, medical practitioners in everyday clinical practice should maintain comprehensive clinical documentation, systematically tracking both rhinoconjunctivitis symptom scores and emotional wellness markers. By combining targeted allergen desensitization with empathetic, proactive mental health surveillance, healthcare providers can ensure holistic care that addresses both physical respiratory symptoms and psychological well-being.

Frequently Asked Questions

Does sublingual immunotherapy increase the risk of developing clinical depression?

Current real-world clinical evidence indicates that sublingual immunotherapy does not increase the risk of developing clinical depression. A comprehensive propensity score-matched study demonstrated that antidepressant initiation rates among immunotherapy users were statistically comparable to non-users. Therefore, clinicians can confidently reassure patients that sublingual desensitization does not trigger mood disorders or necessitate subsequent antidepressant pharmacotherapy.

Why did immunotherapy users have higher crude rates of antidepressant use before matching?

Patients who proactively seek sublingual immunotherapy often exhibit higher baseline health awareness and frequent medical consultations. Furthermore, individuals with burdensome allergic symptoms frequently experience chronic sleep disruption, fatigue, and preexisting emotional distress before starting immunotherapy. Consequently, propensity score matching was essential to balance baseline mental health conditions and accurately evaluate the independent effect of allergy desensitization.

How should clinicians monitor mental health in patients undergoing allergy immunotherapy?

Clinicians should screen for depressive symptoms independently of allergen immunotherapy administration during routine atopic evaluations. Specifically, physicians should evaluate sleep quality, persistent fatigue, and mood fluctuations using validated clinical screening questionnaires. If significant depressive symptoms emerge, providers must refer patients for appropriate psychiatric management, as immunotherapy treats allergic hypersensitivity rather than underlying affective disorders.

Disclaimer: This content is for informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult qualified healthcare providers with any questions regarding clinical management or health conditions. Refer to the latest local and national guidelines for clinical practice.

References

Matsushita R et al. Antidepressant initiation after sublingual immunotherapy in Japanese cedar pollinosis: a real-world propensity score-matched cohort study. Curr Med Res Opin. 2026 Aug 30. doi: 10.1080/03007995.2026.2722388. PMID: 42669179.

Khan J. The Psychological Impact of Allergies and the Benefits of Immunotherapy. J Allergy Ther. 2024;15(2):1000342.

Ciprandi G, Silvestri S. Clinical Evaluation of Allergen Immunotherapy for Allergic Rhinitis. Vaccines (Basel). 2026;14(4):326.

Trikojat K et al. Mental health in allergic rhinitis: Depression and suicidal behavior. Curr Treat Options Allergy. 2017;4(3):328-340.