Degree Name

Doctor of Philosophy


School of Health Sciences


Depression, anxiety and substance abuse are the leading diagnoses of mental illness in Australia, and are most commonly treated with medication and psychological intervention. The Physical Activity Guidelines Advisory suggested that physical activity could protect against symptoms of anxiety and depression, and against the development of an anxiety or depressive disorder. Several nutrients including omega 3 fatty acids, folate, vitamin B12, vitamin B6, zinc, iron, selenium and antioxidants (vitamins C and E) have also been linked to mental health. Despite the growing interest in lifestyle management of mental illness, there has been a dearth of naturalistic studies evaluating interventions in ‘normal practice’ rather than highly supervised clinical trials.

This randomised controlled trial evaluates a lifestyle intervention that was designed to fit within the Australian Enhanced Primary Care Scheme which provides rebates for up to five annual visits to allied health professionals including dietitians and exercise physiologists. GPs in the Illawarra region of New South Wales were invited to refer adult patients currently being treated for depression and/or anxiety. Patients were randomised into either an intervention or attention control group. The intervention consisted of a series of six visits (including assessments) to a dual qualified dietitian/exercise physiologist (DEP) over a 12-week period. DEPs utilised motivational interviewing and activity scheduling to engage patients in individually-tailored lifestyle change.

From 2006 to 2008, 142 patients between the ages of 18 and 84 years were referred to participate. A total of 32 men and 77 women completed an initial assessment. On average, participants were overweight or obese (mean BMI 31.1 kg m-2, mean waist circumference 104.6 cm for males and 92.6 cm for females). Patients reported mild to moderate symptoms of depression, anxiety and stress. Nutrient intakes were similar to those of the general Australian population, however only 17% of participants met the Estimated Average Requirement (EAR) for folate, 57% met the EAR for calcium, and 78% met the EAR for magnesium. Magnesium intake was significantly negatively correlated with reported symptoms of depression. Australian modified Healthy Eating Index (Aus-HEI) scores for diet quality were significantly negatively correlated with Depression Anxiety and Stress Scale (DASS-21) scores. Fifty-three percent of participants demonstrated below average fitness. The National Physical Activity Guidelines were met by 50.5% of participants, but only 18% of participants met the recommendations for vigorous physical activity. Men were significantly more active than women. Total time spent in physical activity, and time spent in vigorous physical activity, were found to be significantly inversely related to depression and total DASS scores. Participants were most likely to choose a combination of both physical activity and dietary goals (n=55), followed by physical activity goals only (n=20). Walking was the most popular physical activity goal (n=69). There was significant improvement over time in DASS scores for the treatment group, but this was not significantly greater than improvements achieved by the control group. Improvements in the control group may have occurred in response to other treatments such as medication or counselling. Both the treatment and control groups improved their participation in physical activity, fitness levels and diet quality over the course of the study period. Intake of iron and folate declined in the control group and improved in the treatment group. Results suggest that patients may be able to initiate lifestyle change with simple activities such as walking or reducing portion sizes, but require professional assistance with more complex dietary modification. Positive feedback was received from both GPs and patients, suggesting that the proposed model of care would be suitable in a primary care environment.