This research describes the design and evaluation of an internet-based universal program for use in schools with adolescent students to prevent common mental disorders and promote mental health. The research began in response to investigations that showed that rates of mental illness in Australian children, teenagers and adults were high, that these illnesses caused significant burden to individuals and society, and that there were insufficient services to treat. When current interventions are unable to alleviate disease burden it is important to focus on prevention. Mental health prevention should target youth before disorders cause disability and restriction of life choices. A review of the mental health prevention literature supported a universal cognitive behavioural approach in schools. Internet delivery was used to maintain content integrity, enable access to people living in regional and remote areas, and to appeal to young people. Internet delivery makes universal prevention cost effective and feasible. The Intervention Mapping approach was used to direct the design of the program. A feasibility study was conducted to gain opinions from students and teaching staff. Changes were made in light of results from this study and 463 students were then exposed to the program in an effectiveness trial. The effectiveness trial was a before-after design with no control group. Results from this trial provided evidence that the program was acceptable and effective for use by teachers in the intervention schools. Also student behaviour and mood changed in beneficial ways after program administration. Specifically, student reported significantly increased knowledge about stress and coping, use of help-seeking behaviours, and life satisfaction, and significantly decreased use of avoidance behaviours, total difficulties and psychological distress. The study design allows causal inferences to be surmised concerning exposure to the intervention and changes in behaviour and mood, but further evidence is needed before firm conclusions about effectiveness can be posited and generalizations made concerning different populations, settings and times. In conclusion, this thesis provides evidence that a computerised, cognitive behavioural mental health prevention program delivered to adolescent school students by teachers can potentially change student coping behaviours and mood in beneficial ways.

The aim of this thesis is to demonstrate the importance of walking to public health. The first part is characterized by epidemiological research. First, a typology for the measurement of walking is developed. A systematic review is conducted of observational studies to determine the health benefits of walking in its own right. Studies consistently confirm that 30 minutes walking on most days of the week is sufficient to reduce the risk of cardiovascular diseases and non-communicable disease risk. Then, a series of epidemiological analyses describes the prevalence and correlates of walking, using multiple health and non-health surveillance data sets. Surveillance data indicate that the prevalence of walking at the above recommended levels is low across all domains. Between 1991 and 2001 an increase in walking occurred, and was the main contributor to reductions in leisure time physical inactivity; however, the proportion of the population who achieved the recommended amount of physical activity by walking did not change in leisure and transport domains. The next part of the thesis is characterized by health promotion research examining the impact of three population-based approaches to increasing walking among Australian adults. The first was an evaluation of a conversion of rail to trail, as an environmental change intervention; the second was a mass media campaign promoting walking to work, and the third was a targeted print media walking program. Providing environmental supports with minimal promotion had no effect on walking. A nation-wide mass media campaign promoting walking to work increased walking and other moderate intensity physical activity, but process evaluation indicated other promotional efforts contributed as well. The targeted print media randomised trial had the greatest effect on walking, but the increases were not greater than spontaneous change in the control. Increases in total physical activity were achieved only when the intervention was supplemented by the use of a pedometer. The expectation that broader approaches to the promotion of walking will bring about changes at the population level, were not corroborated by these case studies. There is a need for enhancement of walking-specific interventions to influence total PA at the population levels.

The aim of this thesis is to demonstrate the importance of walking to public health. The first part is characterized by epidemiological research. First, a typology for the measurement of walking is developed. A systematic review is conducted of observational studies to determine the health benefits of walking in its own right. Studies consistently confirm that 30 minutes walking on most days of the week is sufficient to reduce the risk of cardiovascular diseases and non-communicable disease risk. Then, a series of epidemiological analyses describes the prevalence and correlates of walking, using multiple health and non-health surveillance data sets. Surveillance data indicate that the prevalence of walking at the above recommended levels is low across all domains. Between 1991 and 2001 an increase in walking occurred, and was the main contributor to reductions in leisure time physical inactivity; however, the proportion of the population who achieved the recommended amount of physical activity by walking did not change in leisure and transport domains. The next part of the thesis is characterized by health promotion research examining the impact of three population-based approaches to increasing walking among Australian adults. The first was an evaluation of a conversion of rail to trail, as an environmental change intervention; the second was a mass media campaign promoting walking to work, and the third was a targeted print media walking program. Providing environmental supports with minimal promotion had no effect on walking. A nation-wide mass media campaign promoting walking to work increased walking and other moderate intensity physical activity, but process evaluation indicated other promotional efforts contributed as well. The targeted print media randomised trial had the greatest effect on walking, but the increases were not greater than spontaneous change in the control. Increases in total physical activity were achieved only when the intervention was supplemented by the use of a pedometer. The expectation that broader approaches to the promotion of walking will bring about changes at the population level, were not corroborated by these case studies. There is a need for enhancement of walking-specific interventions to influence total PA at the population levels.