To protect confidentiality, all dates are expressed relative to the initial psychiatric presentation, which is defined as T = 0 (initial presentation). Earlier or later events are described as negative or positive intervals from this time point. A relative timeline of key clinical events is summarized in Table 1. A 17-year-old Japanese female presented with complete amnesia that had begun 3 weeks prior. Her mother, diagnosed with depression 4 years earlier, had been hospitalized approximately 1 month before the initial psychiatric presentation (T =  −1 month) owing to worsening symptoms. Around age 13 years, the patient had been exposed to repeated conflict and domestic violence involving her mother’s partner. Although her mother did not express suicidal ideation at the time, marked mood fluctuations were evident. As the only daughter among four siblings, the patient had assumed an emotional caregiving role from an early age. She lived with her grandmother and younger brother, while her older siblings had already moved out. Despite a complex family background, her developmental milestones were normal, and she demonstrated strong academic and athletic performance, particularly in soccer and softball. Her medical history was unremarkable.

Table 1 Relative timeline of key clinical events

At T =  −5 months, she was found unconscious in a school hallway, showing minimal responsiveness before gradually regaining consciousness over 3 hours. At T =  −2 months, she collapsed in a restroom, displaying fine tremors and mild oxygen desaturation, but recovered during transportation to the hospital. No structural, cardiopulmonary, or metabolic abnormalities were documented in the available records. The transient desaturation was considered most plausibly related to shallow breathing during reduced responsiveness. She also experienced a single prolonged episode of sustained upward eye deviation lasting several hours without documented recurrence. From approximately T =  −1 month, she had daily episodes of transient unresponsiveness of varying durations. These episodes resolved about 3 weeks before T = 0, and were followed by profound retrograde amnesia involving personal, semantic, and procedural memory. Intermittent anterograde amnesia was also noted, with difficulty retaining recent interactions.

Owing to the persistence of symptoms, the patient initially consulted an internal medicine department. Laboratory tests, chest X-ray, electrocardiogram, and brain magnetic resonance imaging (MRI) revealed no abnormalities. She was subsequently referred to psychiatry at T = 0 (initial presentation) under suspicion of a psychogenic etiology. Records from prior emergency evaluations were unavailable, and the patient had no recollection of those events. During the psychiatric assessment, she was accompanied by her grandmother and presented as calm, socially appropriate, and cooperative. Although she reported difficulty recognizing familiar faces, names, and locations, she displayed no distress, and often smiled and spoke positively about school and friendships despite the ongoing memory impairment.

The initial working diagnoses considered were epileptic seizures accompanied by amnesia, dissociative amnesia, and dissociative stupor. Electroencephalogram (EEG) and neurological examinations conducted by neurology ruled out epilepsy. She initially denied significant past psychological trauma, making dissociative disorders less likely at first. However, at T =  +12 days (early follow-up after the initial visit), her amnesia had been improving, and she recalled witnessing her mother’s suicide attempt by hanging 2 years prior. She had experienced distressing flashbacks at the time but had not disclosed them, as her academic and daily activities had been unaffected. Her mother’s recent worsening depression was identified as another significant stressor.

Considering her history, generalized amnesia involving significant life events was attributed to intense psychological stress from her mother’s depression and previous suicide attempt, substantially impairing social functioning. With no evidence of substance use, neurological conditions, medical disorders, excessive fatigue, or other psychiatric disorders, dissociative amnesia was diagnosed. Prior to amnesia onset, she had experienced episodic and repetitive reduced voluntary movement and responsiveness to external stimuli, sometimes maintaining subjective awareness. Given the exclusion of organic and other psychiatric disorders causing impaired consciousness, dissociative stupor was diagnosed. She also exhibited involuntary upward eye deviation (a single prolonged episode without recurrence) without an identifiable organic cause, significantly affecting her daily functioning. In the absence of other medical or psychiatric explanations, conversion disorder was diagnosed. In terms of diagnostic systems, the clinical picture was consistent with ICD-10/ICD-11 categories of dissociative amnesia and dissociative stupor, and with DSM-5 categories of dissociative amnesia and functional neurological symptom (conversion) disorder [1, 2, 4].

Initially, the symptoms caused distress, but strong social support facilitated recovery. Given the strong psychological stressors underlying the symptoms, supportive psychotherapy, psychoeducation, and environmental stabilization were considered the most appropriate treatment approach. Pharmacotherapy was not administered in this case, as psychological interventions were given priority. In addition, considering the patient’s age and psychological adaptability, enhancing self-awareness and coping skills was preferred over medication reliance.

As symptoms resolved after T =  −3 weeks, supportive psychotherapy without medication was continued, emphasizing psychoeducation and gradual memory reintegration. Outpatient follow-ups focused on supportive psychotherapy, reassurance, and psychoeducation on dissociative symptoms, emphasizing their reversibility. The patient and her caregivers received guidance on coping strategies to manage stress and prevent recurrence. Although she occasionally expressed concerns about memory-related difficulties and future uncertainty, these were addressed through structured discussions and problem-solving strategies.

Her memory steadily improved without recurrence of dissociative stupor or conversion disorder symptoms. Family and teacher reports indicated no significant ongoing stressors beyond her mother’s past suicide attempt and recent depressive exacerbation. As her symptoms improved, she adapted well to daily life at home and school, with only mild residual amnesia. Given her overall progress, additional psychotherapeutic interventions were deemed unnecessary. Outpatient visits continued at her request until full symptom remission. As her memory gradually returned and her daily routine stabilized, the patient expressed a growing sense of relief and regained confidence.