For decades, researchers have known that positive mental wellbeing seems to deliver significant improvements in physical health, development, and lifespan – which suggests looking after your mind and mental state is one of the most effective ways to care for the rest of your body as well.

But what's the best way to actually promote personal mental wellbeing? In a new study led by scientists in Australia, researchers cast a wide net, analyzing data from almost 420 randomized trials employing different kinds of psychological interventions to help improve mental states of wellbeing.

The results – a meta-analysis examining data from over 53,000 participants involved in hundreds of psychological experiments – is being billed as the world's largest study of its kind on wellbeing, giving perhaps the most comprehensive overview ever on how interventions can help towards a healthy mind and body.

In the wake of the COVID-19 pandemic and the myriad hardships it has brought all over the world, new insights on how to successfully bolster mental states are in high demand.

"During stressful and uncertain periods in our lives, pro-actively working on our mental health is crucial to help mitigate the risk of mental and physical illness," says mental health researcher Joep Van Agteren from the South Australian Health and Medical Research Institute (SAHMRI).

"Our research suggests there are numerous psychological approaches people should experiment with to determine what works for them."

In itself that might seem obvious, but as the researchers point out, up until now our awareness of psychological interventions' relative efficacy has been obstructed, given much research treats mental wellbeing and mental illness as different things, although they are overlapping concepts in some ways.

Here, the researchers tried to take a broader view, looking at how a wide range of different types of psychological intervention can benefit mental wellbeing, irrespective of any particular theoretical foundation in psychology.

Amongst the many forms of interventions included, two in particular stood out for their consistent associations with positive findings across trial cohorts: mindfulness-based interventions, and multi-component PPIs (positive psychological interventions), which package together a range of treatment methods and activities designed to cultivate positive feelings, behaviors, and thinking patterns.

To a lesser extent, other interventions also appeared to deliver benefits, including acceptance and commitment therapy-based interventions, cognitive therapy, singular PPIs, and interventions focusing on reminiscence.

While the effect sizes of these interventions are often moderate, the analysis here suggests they are linked with positive improvements in wellbeing in both clinical and non-clinical populations – but there's no quick fix, the researchers emphasize.

"Just trying something once or twice isn't enough to have a measurable impact," says co-author Matthew Iasiello, a project coordinator at SAHMRI's Mental Health and Wellbeing program.

"Regardless of what method people are trying out, they need to stick at it for weeks and months at a time for it to have a real effect."

In their paper, the researchers make the same point in a different way.

"Our moderator analysis indicated that improvement in mental wellbeing seems to be related to effort," the team writes.

"While the review did not find a clear linear dose-response effect, with more exposure leading simply to better treatment outcomes, the results do indicate that more intense interventions seem to lead to more pronounced changes."

Another insight by the researchers is that many kinds of psychological interventions can be done safely in volunteer groups or via online platforms, not requiring clinical appointments with professionals such as psychologists.

With mental illness projected to become the largest contributor to disease by 2030, electing to look after yourself with these sorts of activities might not only benefit your own mental wellbeing and health – but the health of the health system too.

"It is therefore potentially a cost-effective addition to current referral pathways and treatment methods," says clinical psychologist Michael Kyrios from Flinders University.

"We need to take everyone's wellbeing seriously and ensure we're taking the necessary steps to improve mental and physical health so we can prevent future complications for ourselves and keep healthcare costs down."

The findings are reported in Nature Human Behaviour.