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Quetiapine-Induced Psychosis: A Rare Adverse Effect (2024 Case Report)

Quetiapine, a second-generation antipsychotic medication, is renowned for its efficacy in managing a spectrum of psychiatric conditions, including schizophrenia, bipolar disorder, and major depressive disorder (MDD).

Despite its broad therapeutic utility and a generally favorable side effect profile, quetiapine’s role in rare instances of inducing psychotic symptoms warrants a closer examination.


  1. Quetiapine’s Mechanism of Action: Quetiapine functions primarily by antagonizing dopamine D2 and serotonin 5-HT2A receptors, with a higher affinity for 5-HT2A, modulating both serotonergic and dopaminergic pathways.
  2. Broad Therapeutic Utility: Beyond its antipsychotic properties, quetiapine is effective as a monotherapy or adjunctive treatment for refractory major depressive disorder and for mood stabilization in bipolar disorder.
  3. Side Effect Profile: Quetiapine is associated with a range of potential side effects, including antimuscarinic, antiadrenergic, antihistaminic, and antidopaminergic reactions, though generally considered to have a more benign profile compared to other psychotropic medications.
  4. Quetiapine-Induced Psychosis: A rare but clinically significant occurrence where quetiapine, paradoxically, may induce psychotic symptoms, underscoring the importance of personalized medicine and careful monitoring.

Source: Cureus (2024)

Case Report: Quetiapine-Induced Psychosis (2024)

Valentine et al. detailed a case report of a 42-year-old male with a history of major depressive disorder (MDD), general anxiety disorder (GAD), and episodic suicidal ideation.

The patient, who had no prior history of psychosis, was admitted to an acute inpatient psychiatric hospital due to worsening depression and expressed suicidal plans.

His medication regimen upon admission included bupropion (300 mg daily), escitalopram (10 mg daily), and alprazolam (0.25 mg up to three times a day as needed).

Notably, the patient disclosed occasional recreational cocaine use.


  • Upon admission, the patient exhibited classic symptoms of depression, including avoidance of eye contact, dysthymic affect, and tangential speech.
  • His Columbia Suicide Severity Rating (C-SSR) scale score was 22, indicating a high level of suicidal risk. He denied any history of hallucinations or delusional thinking.
  • Given his refractory MDD and the inpatient setting’s capability for close monitoring, quetiapine was initiated at a dosage of 100 mg daily to address his depressive symptoms and suicidal ideation.

Treatment & Observation

  • After five days of comprehensive treatment, including psychotherapy and quetiapine administration, the patient showed significant improvement in depressive symptoms.
  • However, on the sixth night, he exhibited new-onset psychotic behavior, engaging in conversations with inanimate objects and displaying heightened agitation.
  • These symptoms were absent before quetiapine initiation.
  • His physiological responses included tachycardia and dilated pupils, with no evidence of external substance use based on urine drug screening.

Intervention & Outcome

  • Quetiapine was discontinued due to the suspicion of drug-induced psychosis, and ziprasidone was introduced, leading to the cessation of hallucinations and stabilization of the patient’s mental state.
  • This clinical decision was supported by the patient’s response to the medication change and the absence of psychosis prior to quetiapine administration.

Diagnostic Evaluation

  • The Naranjo Adverse Drug Reaction Probability Scale was employed to evaluate the likelihood of quetiapine-induced psychosis.
  • The patient scored a three, indicating a possible relationship between quetiapine administration and the onset of psychotic symptoms.
  • This score, derived from a structured assessment, supports the clinical suspicion of quetiapine as a possible trigger for the observed adverse reaction.

(Related: Can Antipsychotics Make You Psychotic?)

42-Year-Old with Psychosis After Quetiapine (2024 Case Report)

Researchers documented a case in which a 42-year-old male patient experienced psychosis after treatment with quetiapine for major depression with suicidal ideation.


  • Clinical Observation: Detailed documentation of the patient’s psychiatric history, clinical presentation, and progression of symptoms following the initiation of quetiapine treatment.
  • Medication Adjustment & Monitoring: The patient’s response to the discontinuation of quetiapine and the subsequent initiation of ziprasidone was closely monitored, including the resolution of psychotic symptoms.
  • Use of Diagnostic Scales: The Naranjo Adverse Drug Reaction Probability Scale was utilized to assess the likelihood that the observed psychotic symptoms were an adverse effect of quetiapine.
  • Literature Review: A comprehensive review of existing literature on quetiapine’s pharmacology, therapeutic use, side effect profile, and previously reported cases of quetiapine-induced psychosis was conducted to contextualize the findings.


  • Clinical Course: The patient developed psychotic symptoms characterized by hallucinations and delusions within days of starting quetiapine, which had not been previously experienced.
  • Medication Response: The psychotic symptoms resolved after quetiapine was discontinued and ziprasidone was introduced, suggesting a possible causal relationship between quetiapine and the onset of psychosis.
  • Naranjo Scale Assessment: The patient scored a three on the Naranjo scale, indicating a possible adverse drug reaction to quetiapine.
  • Literature Context: The case report highlighted the absence of extensive literature documenting quetiapine-induced psychosis, underscoring the rarity and clinical significance of this potential adverse effect.


  • Single Case Report: The findings are based on a single patient case, limiting the generalizability of the results to the broader population.
  • Lack of Rechallenge: Ethical and safety considerations prevented re-administration of quetiapine to the patient, which could have provided more definitive evidence of causality.
  • Potential Confounding Factors: Despite thorough clinical evaluation and monitoring, the potential for confounding factors, including the patient’s past substance use and underlying psychiatric conditions, cannot be entirely excluded.
  • Need for Further Research: The case underscores the need for further empirical research to systematically evaluate the risk and mechanisms of quetiapine-induced psychosis across diverse patient populations.

(Related: How People Feel About Antipsychotics)

Confounding Factors in this Case Report (Quetiapine-Induced Psychosis)

In the exploration of quetiapine-induced psychosis presented in the case report, several confounding factors must be considered.

These factors potentially complicate the interpretation of the causal relationship between quetiapine administration and the onset of psychotic symptoms.

  1. History of Substance Use: The patient’s admitted history of recreational cocaine use, albeit reportedly infrequent, introduces a significant confounding variable. Cocaine’s profound impact on the dopaminergic system could predispose the individual to psychosis, independent of quetiapine use. The temporal gap between cocaine use and the psychotic episode mitigated by the negative drug screen does not entirely exclude the long-term neuropsychiatric consequences of stimulant use as a contributing factor.
  2. Polypharmacy: The patient was on a complex regimen of psychotropic medications, including bupropion and escitalopram, in addition to quetiapine. The interactions between these medications and their cumulative effect on the patient’s neurotransmitter systems could contribute to the development of psychotic symptoms. The synergistic effect of multiple CNS-active agents complicates the isolation of quetiapine as the sole causative factor.
  3. Underlying Psychiatric Disorders: The patient’s pre-existing mental health conditions, including major depressive disorder and general anxiety disorder, represent another layer of complexity. The inherent risk of psychosis associated with these disorders, particularly in severe or treatment-resistant cases, cannot be entirely discounted. This factor complicates the direct attribution of psychotic symptoms to quetiapine use.
  4. Individual Biological Variability: Genetic predispositions or variations in metabolic enzymes (such as those affecting cytochrome P450) could influence the patient’s response to quetiapine, potentially increasing susceptibility to adverse effects. This individual variability in drug metabolism and receptor sensitivity may act as a confounder in assessing the relationship between quetiapine and psychosis.
  5. Lack of Rechallenge: Ethical and clinical considerations often preclude rechallenge with the suspected medication in cases of severe adverse reactions. The absence of rechallenge with quetiapine in this case limits the ability to definitively establish causality based on the recurrence of symptoms upon re-exposure.
  6. Psychosocial Stressors: The report does not detail the patient’s psychosocial context, which can significantly influence psychiatric symptoms. Stressors related to the inpatient psychiatric setting, personal life, or the stress of hospitalization itself could exacerbate underlying conditions or contribute to the emergence of psychosis.

(Related: Can Withdrawal from Antipsychotics Cause Psychosis?)

Mechanisms of Quetiapine-Induced Psychosis

Quetiapine, as an atypical antipsychotic, exerts its therapeutic effects primarily through antagonism of dopamine D2 and serotonin 5-HT2A receptors, among other actions.

While this pharmacological profile is effective in managing various psychiatric disorders, the exact mechanisms by which quetiapine might induce psychosis in rare instances are not fully understood.

However, several theoretical pathways can be proposed based on its pharmacodynamics and the clinical context of the reported case.

  1. Dopamine Receptor Sensitivity: Quetiapine’s antagonistic effect on D2 receptors can lead to an upregulation or increased sensitivity of dopamine receptors in certain brain regions. This paradoxical increase in dopaminergic activity, particularly in the mesolimbic pathway, could potentially contribute to the development of psychotic symptoms in susceptible individuals.
  2. Serotonin-Dopamine Balance: The drug’s higher affinity for 5-HT2A receptors compared to D2 receptors suggests a complex modulation of the serotonin-dopamine balance. While this typically benefits patients by reducing psychotic symptoms and improving mood, an atypical response might disrupt this balance, leading to an overactivation of dopaminergic pathways and the emergence of psychosis.
  3. Impact on Glutamate: Emerging evidence suggests that atypical antipsychotics may also influence glutamatergic neurotransmission. Since glutamate plays a crucial role in cognitive functions and perception, alterations in glutamatergic activity by quetiapine could theoretically contribute to psychotic manifestations.
  4. Pharmacokinetic Variability: Individual differences in the metabolism of quetiapine, possibly related to genetic polymorphisms affecting cytochrome P450 enzymes, can lead to variations in drug levels and responses. In certain cases, this might result in unexpected adverse effects, including the development of psychosis.
  5. Withdrawal from Cocaine Use: Given the patient’s history of cocaine use, the interaction between quetiapine and residual effects or withdrawal from cocaine might have contributed to the onset of psychotic symptoms. Although the drug screen was negative, the long-term changes in dopamine system sensitivity due to cocaine use could interact with quetiapine’s pharmacological action.

Risk Factors for Quetiapine-Induced Psychosis

Identifying specific risk factors for quetiapine-induced psychosis is challenging due to the rarity of this adverse effect.

However, based on the pharmacological properties of quetiapine and the clinical details of reported cases, potential risk factors can be hypothesized.

  • Genetic Predisposition: Genetic variations, especially those affecting drug metabolism (e.g., cytochrome P450 polymorphisms) and neurotransmitter receptor sensitivity, might predispose individuals to atypical responses to quetiapine.
  • History of Substance Use: Patients with a history of substance use, particularly stimulants like cocaine that significantly affect dopaminergic pathways, may be at an increased risk due to altered neurotransmitter system regulation.
  • Preexisting Psychiatric Conditions: While quetiapine is used to treat a variety of psychiatric disorders, individuals with complex or refractory conditions may have an atypical neurochemical profile that responds unpredictably to the medication.
  • Concomitant Medications: The interaction between quetiapine and other medications, especially those affecting neurotransmitter systems or quetiapine’s metabolism, could increase the risk of psychosis.
  • Rapid Dosage Escalation: Although not specifically documented in this case, rapid increases in quetiapine dosage without adequate titration might contribute to adverse reactions, including psychosis, due to abrupt changes in neurotransmitter activity.

(Related: Antipsychotics & Brain Damage, Volume Loss)

Conclusion: Quetiapine Causing Psychosis

This case report sheds light on a rare but clinically significant instance of quetiapine-induced psychosis, challenging the conventional understanding of atypical antipsychotics as solely therapeutic agents in the management of psychiatric disorders.

The detailed analysis of the patient’s clinical presentation, alongside the utilization of the Naranjo Adverse Drug Reaction Probability Scale, underscores the complexity of pharmacological responses and the potential for atypical antipsychotics to induce psychosis in susceptible individuals.

While the precise mechanisms remain speculative, the interaction between quetiapine’s pharmacodynamics and individual patient factors, such as genetic predisposition and history of substance use, emerges as a critical area for further investigation.

Identifying specific risk factors for adverse reactions to quetiapine is imperative for optimizing patient outcomes and tailoring psychiatric care to individual needs.

This case also highlights the importance of vigilant monitoring and readiness to adjust treatment strategies in response to the emergence of new or worsening symptoms.

Overall, this report contributes to the broader discourse on the safety and efficacy of psychotropic medications, advocating for a nuanced and patient-centered approach in psychiatric pharmacotherapy.


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