Case Study: Mirtazapine-Induced Intensification of Hypnagogic Hallucinations in a Young Adult

Case at a Glance

A 20-year-old male with mixed anxiety-depressive disorder presented with a one-year history of hypnagogic visual hallucinations. His symptoms significantly worsened in intensity and frequency three weeks after initiating treatment with Mirtazapine 15mg, prompting concern about the medication's side effects and his family history of bipolar disorder.

Patient's Story

The patient, a 20-year-old male weighing 80kg, reported experiencing visual phenomena for approximately one year. These events occurred exclusively as he was trying to fall asleep or when he would close his eyes in a relaxed state. He described seeing spiders, insects, and faces. A particularly recurrent and disturbing image was the perception of looking down his bed to see two arms reaching over the footboard, as if a figure was hiding underneath. He also noted an unusual ability to accurately visualize his room with his eyes closed, even perceiving the motion of his own hand when waved in front of his face. He had previously dismissed these experiences as a normal part of the brain preparing for sleep.

Initial Assessment

The patient was diagnosed with mixed anxiety-depressive disorder prior to the escalation of his symptoms. Three weeks before seeking further advice, he was prescribed Mirtazapine 15mg daily. Following the initiation of this medication, he reported a marked increase in the vividness of his pre-existing hallucinations. The phenomena expanded to include complex geometric patterns with his eyes closed and, for the first time, simple visual hallucinations with his eyes open in a dark room (seeing spiders on his curtains). Despite the distressing nature of some images, the patient maintained full insight, recognizing that the perceptions were not real. His primary concern stemmed from a family history of bipolar disorder in his mother, leading him to worry if these hallucinations were an early sign of a more severe psychiatric condition.

The Diagnostic Journey

The patient's report was highly characteristic of hypnagogic hallucinations—perceptual disturbances that occur in the transitional state between wakefulness and sleep. These are often considered a benign and relatively common phenomenon. However, the clear temporal relationship between the initiation of Mirtazapine and the significant intensification of these hallucinations strongly suggested a medication-induced side effect. Mirtazapine is known to affect sleep architecture and can cause vivid dreams, which can sometimes bleed into the hypnagogic state. The clinical evaluation focused on distinguishing this side effect from the onset of a primary psychotic disorder. Key differentiating factors were the patient's preserved insight and the absence of daytime hallucinations, delusions, or thought disorganization. While the family history of bipolar disorder warranted caution and monitoring, his current symptom profile was not indicative of a manic or psychotic episode.

Final Diagnosis

1. Mirtazapine-induced exacerbation of hypnagogic hallucinations.
2. Mixed anxiety-depressive disorder (pre-existing diagnosis).

Treatment Plan

The immediate plan involved patient education and reassurance. The patient was informed that hypnagogic hallucinations are typically benign and that their intensification was a known, though not universal, side effect of Mirtazapine. At his scheduled medication review, a discussion was planned to weigh the therapeutic benefits of Mirtazapine for his anxiety and depression against the distress caused by the heightened hallucinations. Treatment options to be considered included:

1. Continuing Mirtazapine with close monitoring, awaiting potential adaptation to the side effect.
2. Reducing the dose of Mirtazapine.
3. Discontinuing Mirtazapine and switching to an alternative antidepressant with a different pharmacological profile.

Outcome and Follow-up

The patient was scheduled for a formal medical review to implement changes to his treatment plan. Follow-up was arranged to monitor both his mood symptoms and the status of his perceptual disturbances after the medication adjustment. He was advised to report immediately if he experienced any new symptoms, particularly hallucinations during full daytime wakefulness, confusion about reality, or any signs of mood elevation, to ensure timely re-evaluation given his family history.