Around 3.2 million Australians live with depression.

At the same time, few Australians meet recommended dietary or physical activity guidelines. What has one got to do with the other?

Our world-first trial, published this week, shows improving diet and doing more physical activity can be as effective as therapy with a psychologist for treating low-grade depression.

Previous studies (including our own) have found “lifestyle” therapies are effective for depression. But they have never been directly compared with psychological therapies – until now.

Amid a nation-wide shortage of mental health professionals, our research points to a potential solution. As we found lifestyle counselling was as effective as psychological therapy, our findings suggest dietitians and exercise physiologists may one day play a role in managing depression.

What did our study measure?

During the prolonged COVID lockdowns, Victorians’ distress levels were high and widespread. Face-to-face mental health services were limited.

Our trial targeted people living in Victoria with elevated distress, meaning at least mild depression but not necessarily a diagnosed mental disorder. Typical symptoms included feeling down, hopeless, irritable or tearful.

We partnered with our local mental health service to recruit 182 adults and provided group-based sessions on Zoom. All participants took part in up to six sessions over eight weeks, facilitated by health professionals.

Half were randomly assigned to participate in a program co-facilitated by an accredited practising dietitian and an exercise physiologist. That group – called the lifestyle program – developed nutrition and movement goals:

• eating a wide variety of foods
• choosing high-fibre plant foods
• including high quality fats
• limiting discretionary foods, such as those high in saturated fats and added sugars
• doing enjoyable physical activity.

The second group took part in psychotherapy sessions convened by two psychologists. The psychotherapy program used cognitive behavioural therapy (CBT), the gold standard for treating depression in groups and when delivered remotely.

In both groups, participants could continue existing treatments (such as taking antidepressant medication). We gave both groups workbooks and hampers. The lifestyle group received a food hamper, while the psychotherapy group received items such as a colouring book, stress ball and head massager.

Lifestyle therapies just as effective

We found similar results in each program.

At the trial’s beginning we gave each participant a score based on their self-reported mental health. We measured them again at the end of the program.

Over eight weeks, those scores showed symptoms of depression reduced for participants in the lifestyle program (42%) and the psychotherapy program (37%). That difference was not statistically or clinically meaningful so we could conclude both treatments were as good as each other.

There were some differences between groups. People in the lifestyle program improved their diet, while those in the psychotherapy program felt they had increased their social support – meaning how connected they felt to other people – compared to at the start of the treatment.

Participants in both programs increased their physical activity. While this was expected for those in the lifestyle program, it was less expected for those in the psychotherapy program. It may be because they knew they were enrolled in a research study about lifestyle and subconsciously changed their activity patterns, or it could be a positive by-product of doing psychotherapy.

There was also not much difference in cost. The lifestyle program was slightly cheaper to deliver: A$482 per participant, versus $503 for psychotherapy. That’s because hourly rates differ between dietitians and exercise physiologists, and psychologists.

What does this mean for mental health workforce shortages?

Demand for mental health services is increasing in Australia, while at the same time the workforce faces worsening nation-wide shortages.

Psychologists, who provide about half of all mental health services, can have long wait times. Our results suggest that, with the appropriate training and guidelines, allied health professionals who specialise in diet and exercise could help address this gap.

Lifestyle therapies can be combined with psychology sessions for multi-disciplinary care. But diet and exercise therapies could prove particularly effective for those on waitlists to see a psychologists, who may be receiving no other professional support while they wait.

Many dietitians and exercise physiologists already have advanced skills and expertise in motivating behaviour change. Most accredited practising dietitians are trained in managing eating disorders or gastrointestinal conditions, which commonly overlap with depression.

There is also a cost argument. It is overall cheaper to train a dietitian ($153,039) than a psychologist ($189,063) – and it takes less time.

Potential barriers

Australians with chronic conditions (such as diabetes) can access subsidised dietitian and exercise physiologist appointments under various Medicare treatment plans. Those with eating disorders can also access subsidised dietitian appointments. But mental health care plans for people with depression do not support subsidised sessions with dietitians or exercise physiologists, despite peak bodies urging them to do so.

Increased training, upskilling and Medicare subsidies would be needed to support dietitians and exercise physiologists to be involved in treating mental health issues.

Our training and clinical guidelines are intended to help clinicians practising lifestyle-based mental health care within their scope of practice (activities a health care provider can undertake).

Future directions

Our trial took place during COVID lockdowns and examined people with at least mild symptoms of depression who did not necessarily have a mental disorder. We are seeking to replicate these findings and are now running a study open to Australians with mental health conditions such as major depression or bipolar disorder.

If this article has raised issues for you, or if you’re concerned about someone you know, call Lifeline on 13 11 14.

Adrienne O’Neil, Professor, Food & Mood Centre, Deakin University and Sophie Mahoney, Associate Research Fellow, Food and Mood Centre, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Would you give up your sense of smell to keep your hair? What about your phone?

A 2022 US study compared smell to other senses (sight and hearing) and personally prized commodities (including money, a pet or hair) to see what people valued more.

The researchers found smell was viewed as much less important than sight and hearing, and valued less than many commodities. For example, half the women surveyed said they’d choose to keep their hair over sense of smell.

Smell often goes under the radar as one of the least valued senses. But it is one of the first sensory systems vertebrates developed and is linked to your mental health, memory and more.

Here are five fascinating facts about your olfactory system.

1. Smell is linked to memory and emotion

Why can the waft of fresh baking trigger joyful childhood memories? And why might a certain perfume jolt you back to a painful breakup?

Smell is directly linked to both your memory and emotions. This connection was first established by American psychologist Donald Laird in 1935 (although French novelist Marcel Proust had already made it famous in his reverie about the scent of madeleines baking.)

Odours are first captured by special olfactory nerve cells inside your nose. These cells extend upwards from the roof of your nose towards the smell-processing centre of your brain, called the olfactory bulb.

From the olfactory bulb they form direct connection with the brain’s limbic system. This includes the amygdala, where emotions are generated, and the hippocampus, where memories are created.

Other senses – such as sight and hearing – aren’t directly connected to the lymbic system.

One 2004 study used functional magnetic resonance imaging to demonstrate odours trigger a much stronger emotional and memory response in the brain than a visual cue.

2. Your sense of smell constantly regenerates

You can lose your ability to smell due to injury or infection – for example during and after a COVID infection. This is known as olfactory dysfunction. In most cases it’s temporary, returning to normal within a few weeks.

This is because every few months your olfactory nerve cells die and are replaced by new cells.

We’re not entirely sure how this occurs, but it likely involves your nose’s stem cells, the olfactory bulb and other cells in the olfactory nerves.

Other areas of your nervous system – including your brain and spinal cord – cannot regenerate and repair after an injury.

Constant regeneration may be a protective mechanism, as the olfactory nerves are vulnerable to damage caused by the external environment, including toxins (such as cigarette smoke), chemicals and pathogens (such as the flu virus).

But following a COVID infection some people might continue to experience a loss of smell. Studies suggest the virus and a long-term immune response damages the cells that allow the olfactory system to regenerate.

3. Smell is linked to mental health

Around 5% of the global population suffer from anosmia – total loss of smell. An estimated 15-20% suffer partial loss, known as hyposmia.

Given smell loss is often a primary and long-term symptom of COVID, these numbers are likely to be higher since the pandemic.

Yet in Australia, the prevalence of olfactory dysfunction remains surprisingly understudied.

Losing your sense of smell is shown to impact your personal and social relationships. For example, it can mean you miss out on shared eating experiences, or cause changes in sexual desire and behaviour.

In older people, declining ability to smell is associated with a higher risk of depression and even death, although we still don’t know why.

4. Loss of smell can help identify neurodegenerative diseases

Partial or full loss of smell is often an early indicator for a range of neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases.

Patients frequently report losing their sense of smell years before any symptoms show in body or brain function. However many people are not aware they are losing their sense of smell.

There are ways you can determine if you have smell loss and to what extent. You may be able to visit a formal smell testing centre or do a self-test at home, which assesses your ability to identify household items like coffee, wine or soap.

5. You can train your nose back into smelling

“Smell training” is emerging as a promising experimental treatment option for olfactory dysfunction. For people experiencing smell loss after COVID, it’s been show to improve the ability to detect and differentiate odours.

Smell training (or “olfactory training”) was first tested in 2009 in a German psychology study. It involves sniffing robust odours — such as floral, citrus, aromatic or fruity scents — at least twice a day for 10—20 seconds at a time, usually over a 3—6 month period.

Participants are asked to focus on the memory of the smell while sniffing and recall information about the odour and its intensity. This is believed to help reorganise the nerve connections in the brain, although the exact mechanism behind it is unclear.

Some studies recommend using a single set of scents, while others recommend switching to a new set of odours after a certain amount of time. However both methods show significant improvement in smelling.

This training has also been shown to alleviate depressive symptoms and improve cognitive decline both in older adults and those suffering from dementia.

Just like physiotherapy after a physical injury, olfactory training is thought to act like rehabilitation for your sense of smell. It retrains the nerves in your nose and the connections it forms within the brain, allowing you to correctly detect, process and interpret odours.

Lynn Nazareth, Research Scientist in Olfactory Biology, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.