Dopaminergic function in the psychosis spectrum: an [18F]-DOPA imaging study in healthy individuals with auditory hallucinations

Abstract

Background: The psychosis phenotype appears to exist in the population as a continuum, but it is not clear if subclinical psychotic symptoms and psychotic disorders share the same neurobiology. We investigated whether the dopaminergic dysfunction seen in psychotic disorders is also present in healthy, well-functioning people with hallucinations.

Methods: We compared dopamine synthesis capacity (using 6-[(18)F]fluoro-L-DOPA [[(18)F]-DOPA] positron emission tomography imaging) in 16 healthy individuals with frequent persistent auditory verbal hallucinations (hallucinating group) with that in 16 matched controls.

Results: There was no significant difference in dopamine synthesis capacity in the striatum, or its functional subdivisions, between groups and no relationship between subclinical psychotic symptom severity or schizotypal traits and dopamine synthesis capacity in the hallucinating group.

Conclusions: Altered dopamine synthesis capacity is unlikely to underlie subclinical hallucinations, suggesting that although there may be a phenomenological psychosis continuum, there are distinctions at the neurobiological level.

Keywords: PET; aetiology; dopamine; hallucination; neurochemistry; psychosis continuum; schizophrenia; subclinical; symptom.

Fig. 1.

Striatal dopamine synthesis capacity (K_i ^cer value/min) for subjects and group means (error bars = SD).

Fig. 2.

Showing the relationship between striatal dopamine synthesis capacity (K_i ^cer value/min) and clinical ratings in the hallucinating group. (a) Total Psyrats Auditory Hallucinations Rating Scale score. There was no significant relationship between the 2 variables (r = −.15, P = .6). (b) Peter’s Delusion Inventory Score. There was no significant relationship between the 2 variables (r = −.14, P = .6). (c) Total Schizotypal Personality Questionnaire Score. There was no significant relationship between the 2 variables (r = .13, P = .63).