Elevated striatal dopamine function in immigrants and their children: a risk mechanism for psychosis

Abstract

Migration is a major risk factor for schizophrenia but the neurochemical processes involved are unknown. One candidate mechanism is through elevations in striatal dopamine synthesis and release. The objective of this research was to determine whether striatal dopamine function is elevated in immigrants compared to nonimmigrants and the relationship with psychosis. Two complementary case-control studies of in vivo dopamine function (stress-induced dopamine release and dopamine synthesis capacity) in immigrants compared to nonimmigrants were performed in Canada and the United Kingdom. The Canadian dopamine release study included 25 immigrant and 31 nonmigrant Canadians. These groups included 23 clinical high risk (CHR) subjects, 9 antipsychotic naïve patients with schizophrenia, and 24 healthy volunteers. The UK dopamine synthesis study included 32 immigrants and 44 nonimmigrant British. These groups included 50 CHR subjects and 26 healthy volunteers. Both striatal stress-induced dopamine release and dopamine synthesis capacity were significantly elevated in immigrants compared to nonimmigrants, independent of clinical status. These data provide the first evidence that the effect of migration on the risk of developing psychosis may be mediated by an elevation in brain dopamine function.

The Search for Environmental Mechanisms Underlying the Expression of Psychosis: Introduction

“…Thus, Selten and colleagues 19 provide an extensive review on the hypothesis that environmental effects, such as minority position, urbanization, traumatization, hearing impairment, and discrimination, may be mediated by "social exclusion" and the experience of "defeat" which in turn may be accompanied by alterations in brain dopamine function. In a direct test of this, Mizrahi and colleagues 20 present experimental neuroimaging work in controls, patients with a psychotic disorder, and CHR individuals, examining the possibility that the risk increasing mechanism of migration and minority position maybe mediated by an elevation in brain dopamine function. In a similarly mixed sample of patients with incident psychotic disorder, CHR individuals, and healthy controls, Klippel et al 21 investigate how stressful contexts and experiences, enhanced threat anticipation, and experiences of aberrant salience combine to increase the intensity of psychotic experiences in daily life using the Experience Sampling Method.…”