The Life Course Epidemiology of Psychotic Symptoms in Schizophrenia and Other Psychoses: from environment to psychosis

John Grace QC PhD Scholarship 2015 -  University College London, Division of Psychiatry,

Supervisor: Dr James B Kirkbride 

Research Student: Jennifer Dykshoorn

Start Date: September 2015
Scientific goal: 

The scientific goal of this proposed PhD project is to (a) test which types of psychotic symptoms are most strongly linked to socio-environmental risk factors, (b) establish 
when such associations are strongest over the life course, and (c) examine the direct and mediated pathways through which such risk factors contribute to psychosis aetiology. 


Schizophrenia risk is strongly linked to urban living and ethnic minority status. We don’t know, however, whether these factors act on specific psychotic symptoms which underpin schizophrenia (i.e. hallucinations, delusions, paranoia, changes in mood, impaired thinking or social withdrawal). In this PhD research project we will use statistical data from two population-based studies to (a) investigate which psychotic symptoms are most strongly linked to detailed social & environmental factors in childhood and adolescence, (b) establish the ages when such associations are strongest, and (c) examine the pathways through which these factors increase risk of symptoms.

Personal Profile

I am a PhD student, working with Dr. James Kirkbride and Dr. Glyn Lewis in the Division of Psychiatry at UCL. My current research focuses on social and spatial determinants of psychotic disorders, including schizophrenia. For part of my research, I am collaborating closely with researchers at the Karolinska Institutet.

My research investigates the timing of exposure to adverse social environments in order to explore how these experiences influence the risk of developing psychotic disorders. I will be using longitudinal data available through record linkages in Sweden as well as the ALSPAC birth cohort from Bristol in order to investigate these questions.          

My research is made possible through the generous support of Mental Health Research UK and UCL Overseas Research Scholarship. 

2016 Report

Psychotic disorders, including schizophrenia and bipolar disorder with psychotic symptoms, are serious mental illnesses that have a debilitating impact on individuals and society. While both genetic and environmental markers have been linked to the development of psychotic disorders, it is unclear whether there are sensitive windows during which exposure to adverse social environments, including migration and social exclusion, increases risk.
My research investigates the timing of exposure to such factors in relation to the development of psychotic disorders, with the hope that by better understanding the timing of exposures can provide important information to what underlying mechanisms are affected.

I am finishing the first analysis for this, where I was able to use Swedish registry data to investigate how timing of migration affects the risk of developing affective and non-affective psychosis. My analysis looked at over 2 million people, and I conducted a survival analysis which revealed an increased risk of psychosis for both first and second-generation migrants. Figures 1 and 2 show the age- and sex- adjusted hazard ratios ((which compare the rate at which diagnoses of psychotic disorders happen in each group (e.g. migrants, second-generation migrants) to the reference group (e.g. Swedish born)) for non-affective and affective psychosis by migrant status. These figures show a significantly increased risk for both diagnostic categories in both first and second-generation migrants, when compared to the Swedish-born (with Swedish-born parents) population.

Figure 1: Age- and sex-adjusted hazard ratios                                 
Figure 2: Age- and sex-adjusted hazard 
for non-affective psychosis by migrant status                                   ratios for affective psychosis by migrant status

* denote significantly increased hazard ratio in that group compared to the
reference category, in this case Swedish born individuals.

I also demonstrated the increased risk of psychosis appears to vary age at which migration occurred. I have been accepted to present these results as part of a symposium at the European Psychiatric Association’s Epidemiology and Social Psychiatry in November. In the next phase of research, where I will be using these data to investigate how timing of maternal migration affects risk among second- generation migrants. I will also examine if the increased risk of psychotic disorders varies according to country of origin. I hypothesize that the adverse stressors may be exaggerated among those who have moved from countries that are very culturally different from Sweden, which in turn may have an increased impact on mental health, including psychotic disorders.

In addition to making progress on my research questions, I have had the opportunity to co-author a book chapter, participate in teaching and lecturing the MSc students, and attending training courses and conferences to increase my knowledge and skills. I was also awarded the UCL Overseas Research Scholarship, which covers the difference between domestic and international fees. This award, in combination with the support from MHRUK, allows me to continue this fascinating research.