Case Report and Analysis of an Intriguing Phenomenon in Schizophrenia: Incubus Syndrome

Introduction

Incubus syndrome is a rare and intriguing psychopathological condition where individuals, particularly women, harbour a strong belief that they are being sexually visited by a demonic presence. The term was derived from medieval European folklore, where it described a demon thought to engage in sexual assault, particularly women while they slept. It is also known by various other names such as incubo, night hag, pnigalion, (classical) nightmare, pnigalium. ¹ Even though this has not yet been classified in the International Classification of Diseases (ICD-11) or the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR), it is still a subject of fascination and debate as this syndrome serves as a testament to the enduring influence of cultural beliefs on human experiences and perceptions of the unknown. We report a case of incubus syndrome in a schizophrenia patient from East India, highlighting the limited available literature on the subject despite numerous cases presented to clinics.

Case Report

A 45-year-old married female with a boy child, hailing from a middle socio-economic background and separated from her spouse since the age of 28, sought help at the psychiatry outpatient department, expressing concerns about recurrent abnormal experiences that baffled both herself and her family.

Diagnosed with schizophrenia, she recounted feeling intensely targeted sexually by a man for the past two and a half months. These encounters were accompanied by vivid hallucinations of a male figure within her home whom she depicted as a malevolent figure with glowing eyes and a menacing demeanour. However, her family members did not mention encountering similar experiences. She further described that throughout the day she would feel a tingling sensation in her genitals and inner thighs, along with sensations of her breast and genitals being touched. She vividly described feeling the rhythmic movement of phallus inside her and could hear the man’s voice instructing her to comply with his commands, accompanied by his groaning. This would excite her. However, these sensations intensified as night fell. She admitted experiencing multiple orgasms throughout the day. Furthermore, she believed that she was being haunted by a spirit, sent by individuals seeking revenge from her for an old conflict. There was no history suggestive of any other sleep-related disorders, post-traumatic stress disorder, cognitive dysfunction or substance use disorder. However, her grandmother had been diagnosed with schizophrenia.

Her blood pressure and pulse were within normal limits. She had a normal BMI. Physical examination of all the systems revealed no abnormalities. Her illness was marked by blunted affect, apathy, thought inhibition, bizarre delusions, somatic delusion, delusional perception, auditory, tactile and visual hallucinations as well as disruptions in biological functioning.

Various tests including complete blood count, blood glucose level, liver function test, renal function test, serum electrolytes, thyroid function test, electroencephalogram and computed tomography of the brain were conducted, revealing no abnormalities. Given the information at hand, a diagnosis of paranoid schizophrenia (F-20.0, according to ICD-10) with incubus syndrome was established. She was on 4 mg of risperidone earlier. Upon the emergence of new symptoms, she was prescribed a daily dosage of 400 mg of amisulpride. Regular monitoring for the past three months has shown an improvement in her symptoms.

Discussion

The history of incubus syndrome is intertwined with cultural beliefs, folklore and medical understanding spanning various eras. Accounts of this syndrome can be found in ancient texts such as the Babylonian Talmud, and the works of ancient Greek and Roman scholars and was formerly ascribed to metaphysical entities. ² Similarly, in Arab culture, comparable sexual behaviours are attributed to jinns. ³ However, with the advancement of medical science, incubus syndrome has been reinterpreted as a psychological disorder characterised by hallucinatory experiences during sleep, often occurring in the context of conditions such as sleep paralysis, narcolepsy or schizophrenia. According to a meta-analysis, the lifetime prevalence of this syndrome is estimated to be 0.11 in normal individuals and 0.41 in schizophrenia patients. ⁴

In 1664, a Dutch physician documented earlier instances where women reported being assaulted by a demon and experiencing paralysis during such encounters. ⁵ These experiences can be described as distressing sexual hallucinations, sometimes referred to as genital hallucinations. Eugen Bleuler, a prominent psychiatrist, observed that in schizophrenia, tactile and bodily hallucinations often initially manifest as sensations in the genital area. ⁶ Research indicates that sexual hallucinations are more commonly reported by women and in schizophrenia patients with prevalence ranging from 1.4% in recently admitted patients to 44% in chronic schizophrenia patients. It is also evident from our case that this syndrome involves multimodal sexual hallucinations and individuals might encounter abnormal spontaneous sensations of orgasm and be troubled by hallucinated smell or other sensations. This phenomenon can be proposed by the involvement of dopaminergic pathways in the causation of sexual hallucinations in schizophrenia patients. ⁷ Additionally, our case report identifies the presence of delusion of control, a criterion necessary for diagnosing schizophrenia, which could be interpreted as expansion of sexual experiences. ⁸ This presentation could also be attributed to Schneiderian first rank symptom, that is, somatic passivity, where individuals report their actions, thoughts and sensations being controlled by an external agency, demarcating between self and other agency. Here, there were mainly passive movements that were felt. ⁹

We have accounts of incubus syndrome reported in sleep-related disorders, panic disorder, and post-traumatic stress disorder. Furthermore, there have been suggestions that incubus syndrome could serve as a precursor to schizophrenia. The individual under our care did not experience any such distress and exhibited a satisfactory response to antipsychotic coverage, establishing a connection between the observed phenomenology and psychosis. Nonetheless, this syndrome has not been categorised differently due to overlapping symptoms with schizophrenia such as auditory hallucinations and delusions, suggesting a common underlying neurological or psychiatric mechanism. This elucidates the reasons for its underreporting in literature.

The change of medication from risperidone to amisulpride on emergence of new symptoms could be attributed to the sexual side effects like decreased libido, erectile dysfunction and ejaculatory disorder. ¹⁰ The shift in medication was done as sexual dysfunction might increase sexual hallucinations. The basis of which is psychologically linked to memories, dream content or fantasies being ‘projected out’ in low states of consciousness, hypnosis or dreaming. ¹¹

Conclusion

This article likely represents the initial case documented from East India and adds to the limited body of literature concerning this syndrome.^8,12,13 Additionally, comprehending the relationship between incubus syndrome and schizophrenia emphasises the significance of tailored treatment strategies.