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Understanding hallucinations outside the context of psychotic disorders

An epidemiological, phenomenological and pathophysiological perspective
PhD ceremony:M.M.J. Linszen, MSc
When:September 27, 2021
Supervisors:prof. dr. I.E.C. (Iris) Sommer, prof. dr. P. Scheltens
Co-supervisor:dr. R.M. Brouwer
Where:Academy building RUG
Understanding hallucinations outside the context of psychotic

Hallucinations have traditionally been studied in the context of psychotic disorders, such as schizophrenia. However, they occur in many different diseases, and even in the general population. The research in this thesis aims at improving understanding of hallucinations in hearing impairment, Alzheimer's disease and the general population.

One of the main findings of this thesis is the association between hearing impairment and auditory hallucinations. The worse the impairment, the higher the percentage of people with recent auditory hallucinations. People may hear music, voices, or the doorbell. In some cases, people experience a lot of distress from their hallucinations.Furthermore, it appears that hallucinations are not common in people with early-stage Alzheimer's disease. If hallucinations do occur, other diseases in which hallucinations can occur should also be considered, such as hearing impairment or dementia with Lewy Bodies.The third part of this thesis provides an overview of the very diverse manifestations with which hallucinations can present themselves in the general population. Also, participants from the general population who have recently heard voices appear to make more mistakes on a language perception task.

With the information from this thesis, physicians can improve education and diagnostic assessment of hallucinations. Our findings also provide clues about underlying mechanisms of hallucinations. Finally, our findings are also relevant for the general public. Often, hallucinations are still accompanied by stigma, or the fear of being thought crazy. This thesis shows a much more nuanced perspective of hallucinations.