Testamentary capacity in patients with bipolar disorder: clinical, temporal, and forensic criteria for assessing lucidity in the testamentary act

Abstract

Introduction: Testamentary capacity is a requirement for the validity of a will, assessed in a task-specific manner and contemporaneously with the act, rather than on the basis of a psychiatric diagnosis considered in the abstract. Bipolar disorder poses a singular challenge to this assessment because of its episodic course, in which mania, depression, and euthymia alternate, each state having a distinct impact on discernment, risk appraisal, and freedom of will. Objective: To integrate the medico-legal literature on testamentary capacity assessment, findings on decision-making and cognition across the three phases of bipolar disorder, and the Brazilian legal framework. Method: This narrative literature review was conducted and reported according to the recommendations of the Scale for the Assessment of Narrative Review Articles (SANRA). Searches were performed in PubMed/MEDLINE in June 2026 and complemented by a targeted review of Brazilian succession-law doctrine and case law, as well as seminal references retrieved from the reference lists of the included studies. Combinations of the terms “testamentary capacity,” “bipolar disorder,” “psychiatry,” “mania,” “legal capacity,” “decision making,” and “undue influence” were used with the Boolean operators AND and OR. Studies and documents addressing testamentary capacity or decision-making competence, decision-making, cognition or neuropsychological functioning in bipolar disorder, and the legal framework applicable to testamentary acts, written in Portuguese, English, or Spanish, were included. Materials without direct relevance to the topic, duplicate records, and sources of low methodological reliability were excluded. Records were screened by title and abstract, potentially eligible documents were read in full, and nineteen sources comprised the final reference set. Selection was guided by conceptual relevance, methodological robustness, and recency. Discussion: A central proposition is advanced: a bipolar disorder diagnosis alone does not invalidate a will, and the assessment of lucidity must be episodic, temporal, and contextual, anchored in the testator’s mental state at the exact moment of signing. The caveat under Brazilian law regarding an already-interdicted testator, for whom the presumption of incapacity operates more rigidly than in common law, is discussed, as is the distinction between capacity and vulnerability to undue influence. Conclusion: A diagnosis of bipolar disorder, considered in isolation, does not invalidate a will. Testamentary capacity should be assessed episodically, temporally, and contextually, integrating the clinical history, the content of any alterations in judgment, and the relationship between the testator and the beneficiaries. A contemporaneous assessment, conducted and documented when the will is executed, provides the most reliable evidence that the expressed wishes corresponded to a state of preserved discernment.