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Clinical psychologist and Visiting Fellow Omid V. Ebrahimi discusses his work here in Oxford and the study he co-leads in Norway – one of the largest of its kind globally.

Omid Ebrahimi


What are you doing here in Oxford?

I am currently three months into a visiting fellowship with the Oxford Precision Psychiatry lab, working on understanding individual differences in how symptoms of depression impact each other over time to obtain a more person-specific understanding of major depressive disorder. It is a pleasure to work with Andrea Cipriani and witness at first-hand the extraordinary work conducted by my lab mates. I am greatly appreciative of how my skills are developing here.


What does your work in Norway focus on?

I am the co-principal investigator, alongside Sverre Johnson, Asle Hoffart and Marieke Helmich, of the Psychological Adaptiveness to Critical Events (PACE) study. This is a large-scale, nationally representative longitudinal investigation which is set to monitor the mental health of Norwegian adults over the next 15 years, until 2038.

The study aims to examine the impact of personal and contextual events on an (inter)national scale, such as loss, economic recession and infectious disease outbreaks, on the development of common mental health disorders, with a particular emphasis on depression and anxiety.

To date, PACE has recruited more than 15,000 adults, of which 3,500 participate in an ecological momentary sub-study, which involves four daily measurements for 30 days per person, resulting in a total of 420,000 observations across individuals. This makes the PACE study one of the largest investigations of its kind to date, and we are grateful to Modum Bad Psychiatric Hospital for hosting this long-term study.


What is unique about this study?

Several factors combine to make this study unique. First, continuing until 2038, it is a 15-year study investigating changes in mental health in the face of forthcoming stressful periods, including personal, national, and global crises. Longitudinal monitoring of the general population across stressful events provides a unique opportunity to identify how critical events may perturbate and put individuals at risk in developing mental health disorders. Second, the study conducts a random probability sample of the adult population through the obtainment of population lists from Norwegian registries, providing a strong sample to investigate changes in mental health over time. And finally, the PACE study combines four unique sources of information to enhance our understanding of mental illness formation.


What are your four classes of data and where are you getting them from?

The study has obtained data from the following information sources from its participants:

1) Information from electronic health records provides us with objective and clinician-rated data, such as hospital visits and medical history.

2) We will also continue to collect longer-term longitudinal data over the 15-year period to measure macro-level changes in mental health across monthly and annual time scales.

3) Having collected ecological momentary assessment data multiple times per day over a monthly time-period to yield 120 assessments per person, we will obtain an understanding of the day-to-day (i.e. micro-level) processes that put individuals at risk for developing mental health disorders.

4) We also collect natural language data by asking participants to tell us about how their mental health changes over time in an unrestricted, open text manner.

While these information sources have been studied in isolation across a range of landmark studies, they have not previously been combined before. This rich and detailed data provides the PACE study with a unique opportunity to improve our understanding of mental health disorders and how they form in the general population.


Could this study be replicated in the UK or other places in the world?

We have just received approval to expand the PACE study with a UK-based sample, where we aim to obtain a baseline sample in the upcoming year.


What are the challenges of this sort of study?

One challenge in such long-spanning studies concerns the retention of participants over time. We have several protocols in place to mitigate this issue and currently observe high retention rates during the first half year of the study.

We also know that psychiatric disorders result from a complex interaction of psychological, environmental, and biological processes. But we have previously largely been precluded from modelling this due to a limited availability of these different data sources in the same group of individuals, lack of granularity in the data on the individual level, and due to a shortage of modelling frameworks allowing for the incorporation and simultaneous study of the complex patterns that these processes form. We have been fortunate enough to obtain some of these key data sources and to recruit a large pool of participants with an extensive number of observations per person, providing us with the resolution and dimensionality to investigate some of these critical patterns.

Nonetheless, the integration of these different data sources is a key issue and there are still gaps in the field concerning the optimal ways to combine such multimodal information sources. This makes the work challenging, but also exciting.


What are you hoping to find out?

As complex systems researchers, we believe that mental health disorders arise and are maintained through reinforcing feedback loops of biopsychosocial processes. Nonetheless, this biopsychosocial model has for a longer period remained compelling in theory, but quite vague in practice. With the granularity of our data and its different sources of information, we hope to advance our understanding about the mechanistic processes involved in this dynamic interplay to identify how adults transition into mental health disorders and how we can prevent them.

As there are likely to be individual differences in how these processes combine over time across individuals, we hope this can bring us closer to obtaining a more precise understanding of mental disorder formation across different segments of the population.