SINGAPORE - A study by the Institute of Mental Health (IMH) has identified for the first time the societal cost of six common mental health disorders here, estimated at about $1.7 billion per year.

It found that the healthcare system or society would be expected to incur $3,938.90 more in total costs a year for an individual associated with these conditions compared with someone without a disorder.

The costs refer to healthcare utilisation costs and productivity loss.

The six common mental health disorders identified in the study are major depressive disorder, general anxiety disorder, bipolar disorder, obsessive compulsive disorder, alcohol abuse and alcohol dependence.

The $1.7 billion figure was derived from a 13.9 per cent prevalence rate of common mental health conditions among adults aged 18 and above, an estimated more than 433,000 persons, said IMH on Monday (Oct 4).

These findings were from the second Singapore Mental Health Study, initiated in 2016, which examined the prevalence of common mental health disorders here, their associated factors, treatment gap and the local adult population's help-seeking behaviour.

The study was led by IMH in collaboration with the Ministry of Health (MOH) and Nanyang Technological University, and funded by MOH and Temasek Foundation.

A total of 6,126 participants representing the population were interviewed face-to-face between 2016 and 2018.

To establish costs, the study focused on four components - direct medical care, indirect medical care, intermediate and long-term care services, and productivity loss.

It found that the main drivers of costs were direct medical care and loss of productivity.

The cost of productivity loss in terms of absenteeism ($1,091.60) and presenteeism ($931) per year was found to be much higher in people with mental disorders than those without, which was $597.90 for absenteeism and $302.90 for presenteeism.

Absenteeism refers to the number of days out of the past 30 when individuals were "totally unable to work or carry out normal activities due to problems with physical health, mental health, or use of alcohol or drugs".

Presenteeism refers to the number of days they had to "cut back on the type or quantity of work" due to the same problems.

The average annual excess costs - or additional expenses in terms of healthcare resource utilisation and productivity loss - incurred by a person with comorbid mental and chronic physical conditions were higher than those borne by someone with mental disorders or chronic physical conditions alone.

Comorbidity refers to the presence of two or more diseases or medical conditions in a patient.

Compared with individuals without any mental disorders, those with mental illness tend to incur lower costs for visits to a primary care doctor (polyclinic doctor), restructured hospital allied health worker (for example, physiotherapist, nurse or medical social worker), dentist and traditional medicine practitioner (such as traditional Chinese medicine). But they chalk up higher bills for visits to a restructured hospital doctor and other private allied health workers.

In terms of services, they incur lower costs for hospital admissions, but higher expenses for accident and emergency as well as intermediate and long-term care services, compared with those without any mental disorders.

"Our findings show a substantial economic burden of mental disorders on our society - both in terms of direct medical costs and loss of productivity - and this is similar to studies done overseas," said Dr Edimansyah Abdin, principal biostatistician at IMH's research division.

He added: "However, the total cost estimate of $1.7 billion is likely to be an underestimation of the true cost as the study did not include costs associated with caregiver burden, the use of justice system, peer support services, medications, supported (re-)employment programmes, other social services, and loss of earnings associated with unemployment.

"Also, our analysis in this study is limited to the six common disorders in Singapore and did not include other disorders such as schizophrenia."

Dr Mythily Subramaniam, assistant chairman of IMH's medical board (research), noted that mental health literacy and destigmatisation efforts are crucial for early intervention.

The provision of appropriate medical care and use of evidence-based practices will help manage the cost of healthcare utilisation, she said.

"A focus on occupational rehabilitation and workplace mental health support can help mitigate productivity loss," she added.

She noted that the prevalence of common mental disorders in Singapore is likely to increase in the future and will result in higher incremental cost to society.

"No country in the world can afford a steep escalation in healthcare costs or productivity loss. This further strengthens the case for prevention, early treatment and ancillary support services," she said.

IMH provides psychiatric, rehabilitative and therapy services, trains psychiatrists and mental health professionals, and carries out mental health research.

The study findings come as the Covid-19 pandemic has shone a light on the importance of mental health.