1. Can major depressive disorder (MDD) be prevented? How do symptoms of depression develop? Can the progression be halted or reversed? Who recovers, who worsens, and what factors influence these outcomes? These are some of the pertinent questions that researchers from the National Healthcare Group (NHG) aim to address through a nationwide longitudinal study on the development and trajectory of depression.
2. MDD, often referred to as depression, is the most common mental health condition in Singapore with 6.3% of the adult population (1 in 16) having had the condition at some point in their lifetime1. The associated burden of disease is substantial, as it can affect the quality of life, functioning, employment, and productivity of individuals living with the condition.
3. Titled Preventing Depression: Investigation in Cohorts of its etiology and Trajectory (PREDICT), the study is led by NHG's specialist centre for psychiatric care in Singapore, the Institute of Mental Health (IMH). It will follow about 3,200 individuals – who have a diagnosis of depression, subsyndromal depression or no depression – aged between 18 and 75 over a period of five years to understand how the diverse risk and protective factors they are exposed to could influence the symptoms of depression. These include biological factors (e.g. age, gender), psychological factors that influence an individual’s thoughts, emotions and behaviours (e.g. self-esteem, resilience, emotional regulation, lifestyle), social factors (e.g. social networks, relationships with family and friends). The study will shed light on what impacts the progression of depression in the local population and help care professionals to identify appropriate interventions or effective preventive strategies.
4. This is the first time that NHG is embarking on a comprehensive longitudinal investigation into the course of depression. While its researchers from IMH have conducted several population-based studies involving depression, such as the Singapore Mental Health Study and the Well-Being of the Singapore Elderly (WiSE) study, they were cross-sectional in nature. This means that the data was collected at a single point in time, allowing researchers to see associations or links between different factors and depression. However, cross-sectional studies do not establish causal or bi-directional relationships (for example, did social isolation lead to depression, or did depression lead to social isolation), which the PREDICT study aims to do.
1Singapore Mental Health Study 2016: Link
5. “Data will be collected at various timepoints so we can better understand how symptoms of depression and their severity change over time as individuals are exposed to a range of risk and protective factors in their day-to-day life. This makes it possible for us to look at how diverse life events and factors influence the development and progression of depression. This, in turn, can help us identify population subgroups who could be more vulnerable to developing depression, giving us an opportunity to intervene early. If we can design appropriate interventions to mitigate the risks they are exposed to, we hope that one day, we would be able to prevent the onset of depression or change the illness trajectory for better outcomes,” says A/Prof Mythily Subramaniam, Assistant Chairman, Medical Board (Research), IMH, NHG and the lead investigator of this study.
6. PREDICT will also shed light on subsyndromal depression (SSD) and its trajectory, an area that is not well understood in Singapore. SSD is a milder form of depression where the symptoms may impact daily life and functioning, but do not meet the diagnostic criteria for MDD.
7. “Subsyndromal depression is a significant risk factor for MDD. Because the symptoms may not be as pronounced, individuals with SSD may go undiagnosed and untreated, increasing their risk of progressing to full-blown MDD. This study will allow us to address important knowledge gaps around the progression of symptoms and recovery, as well as identify modifiable risk factors, such as stress, lifestyle, social support, and how these impact the health of the individuals,” A/Prof Mythily adds.
About the PREDICT study
8. The study aims to recruit 1,229 individuals, aged between 18 and 75, with recent or previous diagnosis of MDD (i.e. depression), 743 with subsyndromal depression, and a control group of 1,229 persons without depression to achieve the following objectives:
- Describe the long-term prognosis of depressive disorders in Singapore. The primary endpoints will include development of comorbidity, suicidality, relapse, treatment non-compliance, resource utilisation, functioning, and recovery among those with depression.
- Examine biopsychosocial determinants, such as chronic physical conditions like diabetes and hypertension, inflammation, emotion regulation and loneliness of the long-term course and consequences of depressive disorders.
- Gain a deeper understanding of the course of subsyndromal depression in Singapore and assess determinants of recovery, progression to depression or other mental disorders, comorbidity, and resource utilisation in this group.
9. Suitable participants will be recruited via referrals from healthcare institutions, such as IMH and NHG Polyclinics, as well as through public outreach.
10. Collection of data began in September 2024, and is currently ongoing. All participants will be followed for five years, during which data will be collected at six time points – at the start of the study to gather baseline information, and once annually after that for up to five years. Participants will undergo comprehensive mental as well as physical health assessments. They may also opt to provide biological samples, such as blood for testing routine blood parameters, metabolic status (e.g. blood sugar and cholesterol) and immunological markers, and hair sample to test for the impact of stressors through cumulative cortisol level. Details on their socio-demographic background, such as age, gender, occupational status, will also be collected.
11. “Biomarkers are also an important aspect of this study,” says Dr Nisha Chandwani, Chief of Department of Mood & Anxiety, IMH, and a co-investigator. “Currently, the diagnosis of depression relies heavily on symptom history, which can be quite subjective and varied. Biomarkers can provide more objective and measurable markers of disease characteristics, which can lead to more accurate, and possibly, earlier diagnosis. Response to treatment also varies from person-to-person, with some people responding better to antidepressants, others to brain stimulation treatments, while some respond better to psychotherapy treatments. Biomarkers can potentially help identify which individuals are more likely to respond to which treatment types, thereby providing a more personalised treatment approach to depression treatment
