Venlafaxine Linked to Probable Induction of De Novo Vocal Tics

The Expanding Spectrum of Antidepressant-Induced Movement Disorders

Antidepressants are cornerstones of therapy for major depressive disorder and anxiety, yet their influence on motor pathways can lead to a variety of involuntary movements [1]. Drug-induced myoclonus, which involves sudden, brief muscle contractions, and other extrapyramidal symptoms are often linked to alterations in serotonin and dopamine signaling within the basal ganglia [2, 3]. While neurodevelopmental tics typically emerge in childhood, the sudden onset of repetitive vocalizations in adults requires a careful differential diagnosis to distinguish between functional behaviors and medication-induced effects [4, 5]. A 2025 systematic review identified level A evidence linking selective serotonin reuptake inhibitors, including citalopram and sertraline, to drug-induced myoclonus [2]. Furthermore, recent clinical evidence suggests that the serotonin-norepinephrine reuptake inhibitor venlafaxine may specifically induce vocal tics, requiring drug discontinuation to achieve symptom resolution [6]. Identifying these rare adverse events is critical for clinicians to ensure patient safety and prevent unnecessary diagnostic escalation.

Clinical Presentation and Quantitative Severity Assessment

The clinical report details the case of a 57-year-old woman who was initially diagnosed with anxiety and prescribed venlafaxine. She demonstrated a positive clinical response to the medication for three months before electing to discontinue the treatment. Following the cessation of therapy, her anxiety symptoms recurred, leading to the decision to re-initiate venlafaxine. Within a few days of restarting the medication, the patient experienced the rapid onset of frequent and distressing vocal tics. This temporal relationship is a critical diagnostic indicator for clinicians, as the symptoms emerged almost immediately upon the re-introduction of the serotonin-norepinephrine reuptake inhibitor. To quantify the severity of the movement disorder, the researchers utilized the Yale Global Tic Severity Scale (YGTSS), a clinician-rated instrument used to assess the nature and impact of tic symptoms. At the time of presentation, the patient received a Total Tic Score of 22, a value that indicates moderate symptom severity. Furthermore, the patient earned a YGTSS impairment score of 20, reflecting a significant negative impact on her daily functioning and quality of life. These objective measures, combined with the patient's report of the tics being highly distressing, underscore the importance of monitoring for extrapyramidal side effects even in patients who previously tolerated the same medication without incident.

Establishing Causality and Distinguishing SNRI Effects

To determine the likelihood that the medication was the direct cause of the movement disorder, the researchers performed a causality assessment using the Naranjo Adverse Drug Reaction Probability Scale (a standardized questionnaire used to determine the probability that an adverse event is related to drug therapy rather than other factors). The patient received a Naranjo score of 7, a value that indicates a probable relationship between the administration of venlafaxine and the subsequent development of vocal tics. This objective assessment is particularly significant for clinicians because it helps differentiate drug-induced symptoms from primary tic disorders or other neuropsychiatric conditions that may emerge during the course of treatment for anxiety. While previous medical literature has documented associations between antidepressants and the development of tics, those cases have historically involved selective serotonin reuptake inhibitors (SSRIs) or atypical antidepressants. Specifically, prior reports have linked the use of Sertraline (an SSRI) and Mirtazapine (an atypical antidepressant) to the onset of motor tics. However, this case represents the first reported instance of venlafaxine-induced vocal tics, marking a departure from the established literature which had not previously associated serotonin-norepinephrine reuptake inhibitors (SNRIs) with this specific side effect. Furthermore, this study is the first to report vocal tics specifically in association with any antidepressant medication, as previous documented cases were limited to motor manifestations.

Mechanisms of Dopaminergic Dysregulation and Management

Venlafaxine is a serotonin norepinephrine reuptake inhibitor (SNRI) frequently prescribed for the management of major depressive disorder and generalized anxiety disorder. While it is generally considered a safe and well-tolerated medication, its use is associated with common side effects such as nausea, insomnia, and tremors. Beyond these systemic issues, venlafaxine has been linked to neuropsychiatric side effects, most notably akathisia, a movement disorder characterized by a subjective feeling of inner restlessness and a compelling need to be in constant motion. Although several antidepressants have been associated with the development of motor tics, this study identifies a unique risk for vocal tics, which have not been previously reported in the literature for this class of medication. The researchers propose that the pathophysiology of these vocal tics involves a complex interaction between serotonergic augmentation and dopaminergic dysregulation in fronto-striatal circuits, which are the neural pathways connecting the frontal lobe to the basal ganglia that mediate motor and cognitive control. Under this model, the increased serotonin levels provided by the SNRI may indirectly modulate dopamine concentrations. This modulation can trigger the expression of tics in susceptible individuals who may have a lower threshold for dopaminergic fluctuations. For the practicing clinician, recognizing this potential side effect is vital for patient safety. The findings suggest that early detection and discontinuation of the medication can prevent further complications and lead to complete symptom resolution, ensuring that drug-induced vocalizations are not misdiagnosed as primary psychiatric or neurological disorders.

References

1. Revet A, Montastruc F, Roussin A, Raynaud J, Lapeyre‐Mestre M, Nguyen TTH. Antidepressants and movement disorders: a postmarketing study in the world pharmacovigilance database. BMC Psychiatry. 2020. doi:10.1186/s12888-020-02711-z

2. Rissardo JP, Caprara ALF, Bhal N, Repudi R, Zlatin L, Walker IM. Drug-Induced Myoclonus: A Systematic Review. Medicina. 2025. doi:10.3390/medicina61010131

3. Janssen S, Bloem BR, Warrenburg BPVD. The clinical heterogeneity of drug-induced myoclonus: an illustrated review. Journal of Neurology. 2016. doi:10.1007/s00415-016-8357-z

4. Cavanna AE, Caimi V, Capriolo E, et al. Neurodevelopmental Tics with Co-Morbid Functional Tic-like Behaviors: Diagnostic Challenges of a Complex Tourette Syndrome Phenotype. Brain Sciences. 2025. doi:10.3390/brainsci15050435

5. Mainka T, Balint B, Gövert F, et al. The spectrum of involuntary vocalizations in humans: A video atlas. Movement Disorders. 2019. doi:10.1002/mds.27855

6. Alturaymi MA, Alnakshabandi K. Case Report: A rare phenomenon of venlafaxine induced vocal tics. Frontiers in Psychiatry. 2026. doi:10.3389/fpsyt.2026.1797640